Some Linguistic Hypotheses

* I think that it is very likely that the Korean language family and the Japanese language family are related, even if it is challenging to find "smoking gun" evidence of it today. Japanese may have also have some Manchurian linguistic influence. The broader Altaic hypothesis has less strong support, but there may be something to it.

* I think that it is very likely that the Dravidian language family was influenced by an African language family, with the vectors of that transmission probably being people from the Horn of Africa who also brought some key African Sahel domesticates to Southern India around the time of the South Indian Neolithic ca. 2500 BCE. 

* The Harappan language is almost surely not Indo-European, not Dravidian, and not Munda as a language family. It could conceivably have some connection to language isolates in the general region known as Indo-Pacific languages, or it might not. It is probably the main substrate influence on Sanskrit and through Sanskrit on the other Indo-European languages of India. The script associate with it was probably a proto-script, like a set of emojis or trademarks, and not a full written language. The same is true of the early Vinca script used in the Neolithic Balkans.

* I think that it is very likely that Indo-Aryans (Sanskrit speaking derived people) conquered almost all of India sometime in pre-history and imposing their language and the Hindu religion (although not as faithfully to some of its tenants like vegetarianism), except a small last stronghold, more or less in the vicinity of the modern city of Visakhapatnam, which then reconquered territory from the Indo-Aryans, restoring their dialect of the Dravidian language, but not effectively displacing the Hindu religion that the Indo-Aryan conquerors brought with them. This is why the Dravidian language family seems younger than it really is; it's historic linguistic diversity was wiped out at this point with most of its variants extinguished at this time. As I noted in a post at Wash Park Prophet:

[A]reas that are linguistically Indo-Aryan are more likely to be vegetarian than areas that are linguistically Dravidian, Munda or Tibeto-Burmese. Meat eating may reflect a thinner Indo-Aryan influence even in places that experienced a language shift to Indo-Aryan languages. Vegetarianism may alternatively reflect a stronger influence from the pre-Indo-Aryan Harappan society.

* Brahui, a Dravidian language pocket found far from the geographic range of the other Dravidian language, probably was not within the historic range of the Dravidian languages. Instead, it is probably a result of language shift through elite dominance around 1000 CE or so, by some foreign Dravidian warlord or king.

* Sometime around the Copper Age (a.k.a. the Eneolithic) in Anatolia, people from the eastern highlands brought the Hattic language (which preceded the Hittite language) to Anatolia. It is related to Kassite, other Iranian highland languages, and more remotely to most of the Caucasian languages (which are related to each other even if the connections are hard to establish), to Sumerian, and probably to Elamite. It is also probably related to Minoan. One of the litmus tests of all of these languages is that they were ergative. 

Hattic probably replaced the Neolithic language(s) of Anatolia, including the Western Neolithic language which spread across Europe in two main branches, the Linear Pottery culture (LBK) to through the rivers of the north, and the Cardial Pottery culture to more or less along the Mediterranean coast, which was very different from Hattic. The Western Anatolian Neolithic languages were the substrate languages for the Indo-European language in most of Europe, but not in Anatolia where the Hattic language was the substrate. Hattic substrate influence is the reason that Anatolian Indo-European languages like Hittite seem so diverged from other Indo-European languages, because the Hattic society was much healthier when the Indo-Europeans arrived than in other places where the Indo-Europeans conquered Neolithic societies in a state of collapse. The most basil branch of Indo-European was probably that spoken in the Tarim Basin, which was on a frontier with almost no substrate influence.

* It is very likely that the languages of the European hunter-gatherers are completely lost. The Uralic languages arrived much later. In the Americas and Japan and Australia, we know that indigenous hunter-gather language substrates had very little impact on the food producing conquerer languages, even when indigenous peoples made a large genetic contribution to the people speaking the food producer languages.

* Basque, therefore, is very unlikely to be an indigenous European hunter-gatherer language. It could be the last survivor of the language family of the first farmers of Europe rooted in Western Anatolia frmo around 6000 BCE to 4000 BCE, or it could reflect a very distant outpost of a Copper Age language probably in the same language family as Hattic and Minoan. I probably lean towards the Neolithic hypothesis, as the corpus of Hattic (which remained a written liturgical language for a thousand years after the Hittites took over) and of Basque are both large enough that a connection would have been established by linguists by now if it was present, even though both are ergative languages, but the rarity of ergative languages outside the West Asian highlands, ancient Mesopotamia, and places to the east of that, favor a copper age origin for it. The Paleo-Hispanic languages may have all been a coherent group and Tartessos in Southwest Iberia was metal rich and a strong candidate for the source for Plato's Atlantis story. The "Tartessian culture was born around the 9th century B.C. as a result of hybridization between the Phoenician settlers and the local inhabitants. Scholars refer to the Tartessian culture as "a hybrid archaeological culture".

* We know the Etruscan, Raetic, and Lemnian (together called the Tyrsenian languages, an areal designation, since while the connection of Etruscan and Raetic is pretty solid, the linguistic family connection to Lemnian is not, and possibly Camunic as well, although it could also be related to Celtic) are also not Indo-European languages and pre-date Indo-European:

• Etruscan: 13,000 inscriptions, the overwhelming majority of which have been found in Italy; the oldest Etruscan inscription dates back to the 8th century BC, and the most recent one is dated to the 1st century AD.
• Raetic: 300 inscriptions, the overwhelming majority of which have been found in the Central Alps; the oldest Raetic inscription dates back to the 6th century BC.
• Lemnian: 2 inscriptions plus a small number of extremely fragmentary inscriptions; the oldest Lemnian inscription dates back to the late 6th century BC.
• Camunic: may be related to Raetic; about 170 inscriptions found in the Central Alps; the oldest Camunic inscriptions dates back to the 5th century BC.

The ergative substrate influence probably explains its presence in Indo-European Pashto, Kurdish languages and Indo-Aryan languages, which was shared with Basque and is absent from most Indo-European languages. It suggest that Harappan was probably ergative. The Tyresnian languages apparently non-ergative character suggests that they aren't part of the same language family as Basque, and tends to favor a Copper Age origin for Basque rather than a Neolithic origin for it.

But we haven't deciphered them very well since the corpus of those writings has mostly been lost, and what we have left is mostly monolingual and short. We can't even say with completge confidence that they were all in the same language family, although ancient Rhaetic spoken to the north of Etruscan (not linguistically related to the similarly named modern Indo-European minority language of Switzerland) was probably in the same language family with Etruscan. somewhat conflicting historical evidence suggests that Lemnians were migrants from the Alps and/or northern Italy, probably during the Greek dark ages after Bronze Age collapse had run its course.

We also don't know much about the substrate language that influenced Mycenaean Greek.

An Electroweak Centric Model For Standard Model Mass Generation

The basic intuitive gist of the proposal of this paper is one that I've entertained myself, although I don't have the theoretical physics chops to spell it out at this level of formality and technical detail (and I'm really not qualified to evaluate the merits to this proposal at that level). I've seen one or two other papers (not recent ones) that take a similar approach.

The ratio of the electron mass to the lightest neutrino mass eigenstate is roughly the same as the ratio of the electromagnetic coupling constant to the weak force coupling constant, and both are masses are similar to what would be expected from the self-interactions of electrons and neutrinos via the electromagnetic and weak forces with themselves. Electrons interact via both of these forces, while neutrinos interact only via the weak force.

The down quark mass is about twice as much as the up quark mass, just as the absolute value of the down quark electromagnetic charge is twice the absolute value of the up quark electromagnetic charge. All quarks have the same magnitude of strong force color charge. And all of the fundamental fermions of the Standard Model have the same magnitude of weak force charge. Quarks interact via the strong force, the electromagnetic, and the weak force, so their self-interactions might be expected to be larger than for the electron which doesn't interact via the strong force.

Figuring out how this can work in concert with the three fundamental fermion generations is particularly challenging. I'm inclined to associate it with a W boson mediated dynamic process that sets the relative values of the Higgs Yukawas. This paper doesn't attempt to look beyond the first generation of fundamental fermions in implementing its model.

I'm not thrilled with the "leptoquark" component of this theory, but the fact that it gives rise to neutrino mass without either Majorana mass or a see-saw mechanism is very encouraging.

In the Standard Model of elementary particles the fermions are assumed to be intrinsically massless. Here we propose a new theoretical idea of fermion mass generation (other than by the Higgs mechanism) through the coupling with the vector gauge fields of the unified SU(2) ⊗ SU(4) gauge symmetry, especially with the Z boson of the weak interaction that affects all elementary fermions. The resulting small masses are suggested to be proportional to the self-energy of the Z field as described by a Yukawa potential. Thereby the electrically neutral neutrino just gets a tiny mass through its Z-field coupling. In contrast, the electrically charged electron and quarks can become more massive by the inertia induced through the Coulomb energy of the electrostatic fields surrounding them in their rest frames.

Eckart Marsch, Yasuhito Narita, "On the Lagrangian and fermion mass of the unified SU(2) ⊗ SU(4) gauge field theory" arXiv:2508.15332 (August 21, 2025) (13 pages).

The introduction of the paper is as follows:

According to the common wisdom of the Standard Model (SM) of elementary particle physics, the fermions are intrinsically massless, but they gain their masses via phase transition from the vacuum of the Higgs field. However, this notion introduces many free parameters (the Yukawa coupling constants) that are to be determined through measurements. These have been made at the LHC only for some members of the second and third family of heavy leptons and quarks, yet not for the important first family of fermions, of which the stable and long-lived hadrons form according to the gluon forces of quantum chromodynamics (QCD). 

Here we just consider the first fermion family of the SM and propose a new idea of the fermion mass generation. The key assumption is that their masses may be equal to the relevant gauge-field energy in the rest frames of these charged fermions carrying electroweak or strong charges. Their masses are suggested to originate from jointly breaking the chiral SU(2) symmetry combined with the hadronic isospin SU(4) symmetry, as described in the recent model by Marsch and Narita, following early ideas of Pati and Salam and their own work. Unlike in the SM, in their model both symmetries are considered as being unified to yield the SU(2) ⊗ SU(4) symmetry, which then is broken by the same procedures that are applied successfully in the electroweak sector of the SM. 

The outline of the paper is as follows. We briefly discuss the extended Dirac equation and its Lagrangian including the Higgs, gauge-field and fermion sectors. Especially, the covariant derivative is discussed and the various gauge-field interactions are described. Also the different charge operators (weak and strong) are presented. Then the CPT theorem is derived for the extended Dirac equation including the gauge field terms. The remainder of the paper addresses the idea of mass generation from gauge field energy in the fermion rest frame. Finally we present the conclusions.

The paper's conclusion states:

In this letter, we have considered a new intuitive idea of how the elementary fermions might acquire their finite empirical masses. We obtained diagonal mass matrices as Kronecker products within the framework of the unified gauge-field model of Marsch and Narita. The mass matrices still commute with the five Gamma matrices of the extended free Dirac equation without gauge fields. However, when including them the chiral SU(2) and the hadronic SU(4) symmetries both are broken by the mass term. Thus, the breaking of the initial unified SU(2) ⊗ SU(4) symmetry by the Higgs-like mechanism gives the fermions their different charges as well as specific masses. 

In the SM the initial common mass m is assumed to be zero, and then the Dirac spinor splits into two independent two-component Weyl spinors. But when the gauge fields are switched on, their self-energy gives inertia and thus mass to the fermions in their rest frame. The breaking of gauge symmetry yields the electromagnetic massless photon field E(µ) and the weak boson field Z(µ), which becomes very massive via the Higgs mechanism. It also induces inertia for all eight fermions, yet the resulting masses are rather small owing to the very small Compton wavelength of the Z boson. The neutrino and electron can acquire masses in this way, which yet differ by six orders of magnitude. The hadronic charge of the leptons is zero, and thus they decouple entirely from QCD. It is responsible by confinement through the gluons for the mass of the various resulting composite fermions, in particular for the proton mass. 

The masses of the light fermions are thus argued to originate physically from the major self-energy of the electrostatic field as well as from the minor self-energy of the Z-boson field, which is proportional to the Higgs vacuum that determines the Z-boson mass. It is clear, however, that the masses of heavy composite hadrons, in particular of the proton and neutron, involve dominant contributions from the energy of the binding gluon fields, as the QCD lattice simulations have clearly shown. 

In conclusion, the extended Dirac equation contains a physically well motivated mass term. It remedies the shortcoming of the SM that assumes massless fermions at the outset, whereas the empirical reality indicates that they are all massive. Therefore, the neutrino cannot be a Majorana particle, as it has often been suggested in the literature. This notion is in obvious contradiction to the observed neutrino oscillation, implying clearly finite masses. Chiral symmetry is broken in our theory, yet the parity remains intact. 

Finally, we like to mention the masses of the heavy gauge bosons involved in the above covariant derivative and related matrix. In the reference of the particle data group we find in units of MeV/c^2 the values: M(Z) = 91.2 and M(W) = 80.4. For the “leptoquark" boson V we obtain M(V) = 35.4. For the sum of these masses we find the following surprising results: M(V) + M(Z) = 126.6, which equals within less than a one-percent margin the measured mass of the Higgs boson, M(H) = 125.3. Also, M(W) + M(Z) = 171.6, which again equals within less than a one-percent margin the measured mass of the top quark, M(T) = 172.7. Whether this is just a fortuitous coincidence or indicates a physical connection has to remain open. 

My Confidence In Various Physics Hypotheses

There are various unresolved questions in physics about which I have an opinion. I'm not 100% sure of any of them, but more sure of some than others.

In this post, I give my subjective probabilities for various possibilities, in numbers rounded to avoid spurious accuracy and to increments not less than 1% (even if the true probability expressed as 1% is a bit less than 0.5%):

1. Dark matter phenomena:

* Dark matter phenomena are explained by general relativity or subtle modifications or quantum gravity, that only discernible in weak gravitational fields: 90%

* Dark matter phenomena are explained by a 5th force or a singlet ultralight dark matter boson: 6%

* Dark matter phenomena are explained by dark matter particles of micro-eV to TeV mass: 3%

* Dark matter phenomena are explained by dark matter particles of greater than TeV mass (including composite dark matter candidates such as MACHOs, primordial black holes, and stable heavy hadrons in addition to heavy fundamental particles): 1%

2. Dark energy phenomena:

* Dark energy phenomena are an emergent result of the same gravitational effects that give rise to dark matter phenomena (and do not violate mass-energy conservation): 60%

* Dark energy phenomena are equivalent to the cosmological constant of general relativity: 15%

* Dark energy phenomena exist and are fundamental and not just a side effect of dark matter phenomena, but dark energy is not a constant: 15%

* Dark energy phenomena are a result of flawed astronomy methods and don't really exist: 10%

3. The Lambda CDM model:

* The Lambda CDM model is deeply flawed (even though it may be a useful crude first order approximation): 95%

* The Lambda CDM model is basically correct (although it may omit some minor factors like neutrino masses): 5%

4. Cosmological inflation:

* Cosmological inflation did not happen: 85%

* Some form of cosmological inflation happened: 15%

5. Quantum gravity:

* Gravity is fundamentally a quantum phenomena involving gravitons in Minkowski space: 65%

* Gravity arises from a discrete or quantum space-time (whether or not it also has gravitons): 15% 

* Gravity is emergent from Standard Model forces: 10%

* Gravity is fundamentally a classical and deterministic phenomena: 10%

6. Universe scale asymmetry:

* The universe is not homogeneous and isotropic at the largest possible scales: 65%

* At the largest possible scales, the universe is homogeneous and isotropic: 35%

7. Maximum density:

* There is no physical constraint on maximum mass-energy density: 65%

* There is a maximum mass-energy density greater than the mass-energy density of a minimum mass stellar black hole (such as a Planck scale limitation): 20%

* There is a maximum mass-energy density close to the mass-energy density of a minimum mass stellar black hole: 15%

8. Supersymmetry:

* There is no version of supersymmetry that exists: 99%

* Some version of supersymmetry exists: 1%

9. String Theory:

* Reality is not fundamentally described by string theory: 98%

* Reality is fundamentally described by string theory: 2%

10. Fundamental fermions:

* The Standard Model includes all of the fundamental particles that are fermions: 95%

* The Standard Model omits up to five fundamental fermions (none of which are additional generations of existing Standard Model fundamental fermions) such as a dark matter particle(s) or right handed neutrinos or supersymmetric partners of Standard Model bosons: 4%

* The Standard Model omits at least one additional generation of Standard Model fermions, and/or omits more than five additional fundamental fermions: 1%

11. Fundamental bosons:

* The Standard Model includes all of the fundamental particles that are bosons other than a possible massless spin-2 graviton: 85%

* The Standard Model omits additional fundamental particles that are bosons beyond a massless spin-2 graviton (e.g. additional Higgs bosons, dark matter bosons, dark matter self-interaction bosons, X17 bosons, bosons involved in neutrino mass generation, bosons involved in cosmological inflation and/or dark energy, fifth force carrying bosons, scalar or vector gravitons, massive gravitons, leptoquarks, supersymmetric partners of Standard Model fermions): 15%

12. Sphalerons:

* Sphaleron interactions are physically possible: 50%

* Sphaleron interactions are not physically possible: 50%

13. Stable heavy hadrons:

* There are no stable or metastable hadrons other than the proton and neutron: 95%

* There are stable or metastable hadrons other than the proton and neutron: 5%

14. Stable heavy elements:

* There are no chemical elements with an atomic number in excess of 118 with a half-life of more than 30 seconds: 65%

* There are chemical elements in "islands of stability" with an atomic number in excess of 118 with a half-life of more than 30 seconds: 35%

15. Neutrino mass:

* Neutrinos have Majorana mass: 10%

* Neutrino mass arises from a see-saw mechanism with one or more heavy right handed neutrinos: 5%

* Neutrino mass arises from some other mechanism not yet widely considered: 85%

16. Sterile neutrinos:

* Right handed sterile neutrinos with the same mass as left handed neutrinos exist: 1%

* One or more sterile neutrinos that oscillate or interact with left handed neutrinos, and masses not identical to left handed neutrinos, exist: 2%

* The three left handed neutrinos of the Standard Model are the only neutrinos that exist: 97%

17. Neutrino mass hierarchy:

* The neutrino masses have a "normal" hierarchy: 95%

* The neutrino masses have an "inverted" hierarchy: 5%

18. CP Violation by neutrinos:

* The PMNS matrix exhibits maximal CP violation: 8%

* The PMNS matrix exhibits near maximal CP violation: 85%

* The PMNS matrix exhibits low levels of CP violation: 5%

* The PMNS matrix does not allow for CP violation in neutrino oscillation: 2%

19. Non-standard neutrino interactions:

* There are no non-standard neutrino interactions (i.e. interactions beyond neutrino oscillations and weak force interactions) to be discovered: 90%

* There are some non-standard neutrino interactions: 10%

20. Lepton number and baryon number violation:

* Lepton number and baryon number are always conserved: 50%

* Lepton number and baryon number are only violated in sphaleron interactions: 45%

* Lepton number and baryon number are violated in non-sphaleron interactions (such as neutrinoless double beta decay, proton decay, flavor changing neutral currents, etc.): 5%

21. LP & C:

* The sum of the squares of correctly defined masses of the fundamental particles is equal to the sum of the Higgs vacuum expectation value: 60%

* The sum of the squares of correctly defined masses of the fundamental particles is not equal to the sum of the Higgs vacuum expectation value: 40%

22. Koide's Rule:

* Koide's rule for the masses of charged leptons is true to at least one part per 100,000: 90%

* Koide's rule for the masses of charged leptons is violated by more than one part per 100,000: 10%

23. An extended Koide's rule for quarks:

* The quark masses obey some extended version of Koide's rule: 70%

* The quark masses do not obey some extended version of Koide's rule: 30%

24. The physics desert:

* There are no beyond the Standard Model high energy physics to be discovered between the highest energy scale reached by the Large Hadron Collider (about 10^4 GeV), and energy scales a billion times greater than the highest energy scale reached by the Large Hadron Collider  (about 10^13 GeV): 85%

* There are new high energy physics to be discovered between the highest energy scale reached by the Large Hadron Collider (about 10^4 GeV), and energy scales a billion times greater than the highest energy scale reached by the Large Hadron Collider  (about 10^13 GeV): 15%

25. Planet Nine:

* Planet Nine exists: 65%

* Planet Nine does not exist: 35%

Inflationary Cosmology

I'm skeptical of all of the theories described in the abstract below, but I lack the expertise to say with confidence that none of them are correct. 

I am skeptical because, in short, I think that a more accurate description of gravity which gives rise to apparent dark matter and dark energy phenomena, and a mirror universe model in which an anti-matter universe very similar to our own flows backwards in time from the Big Bang, is likely to explain the observations that inflationary cosmology seeks to explain without requiring an exceedingly brief moment of cosmological inflation very shortly after the Big Bang. 

There are peer reviewed published articles that make claims along these lines, but I haven't devoted the time necessary to gain a firm grasp of this literature.

We give a brief review of the basic principles of inflationary theory and discuss the present status of the simplest inflationary models that can describe Planck/BICEP/Keck observational data by choice of a single model parameter. In particular, we discuss the Starobinsky model, Higgs inflation, and α-attractors, including the recently developed α-attractor models with SL(2,ℤ) invariant potentials. We also describe inflationary models providing a good fit to the recent ACT data, as well as the polynomial chaotic inflation models with three parameters, which can account for any values of the three main CMB-related inflationary parameters A(s), n(s) and r.

Renata Kallosh, Andrei Linde, "On the Present Status of Inflationary Cosmology" arXiv:2505.13646 (May 19, 2025).

Another Dark Matter Particle Model

Overview: An Improvement But Worse Than MOND

Another day, another dark matter particle model. 

This time, a spin-0 massive scalar boson and a spin-1 massive vector boson. Unsurprisingly with the additional degree of freedom that two bosonic dark matter particles can provide relative to single dark matter particle models, it can fit the data a little better than most one parameter dark matter particle models.

The authors "fix the vector boson mass µV = 9 × 10^−26 eV across all galaxies[.]" They allow "the scalar boson mass to vary in the range µS ∈ [10^−10, 10^−16] eV." [Ed. I have converted the MeV units used in the paper for the scalar boson mass to eV units for ease of comparison.]

The vector boson mass is (as is typical of ultralight bosonic dark matter models) of the same order of magnitude as the mass-energy of a typical graviton (for which there is also an obvious theoretical basis for gravitons to vary in mass-energy), suggesting a convergence towards the predictions of a gravitationally based explanation for dark matter phenomena with properties similar to a massless tensor (spin-2) graviton.

The second scalar bosonic dark matter particle found in dark matter sub-halos, however, has less of a clear analog for that mass scale, although the behavior of a scalar boson and a tensor boson have a lot of similarities. The authors of the paper note that:"The origin of this second DM source is unknown, which somehow points to a limitation of the model."

The model doesn't explain why the mass of the scalar bosonic dark matter candidate varies in average mass by a factor of a million from one galaxy to another, despite the fact that all of the bosonic dark matter of both types is assumed to be in its ground state in every galaxy, which is necessary for it to produce the assumed halos shapes. 

To be charitable, however, the number of sub-halos times the mass of each sub-halo could be addressed by varying the number of sub-halos rather than the mass of the dark matter particles in each sub-halo. 

But this would create a different problem. The size of each dark matter sub-halo in the model is basically a function of the mass of the scalar bosonic dark matter candidate (related to its reduced Compton wave length), but not all dark matter sub-halos that are inferred from rotation dynamics and gravitational lensing are the same size.

With three parameters: a fixed vector dark matter particle mass, a scalar dark matter particle mass which can be fit to the data on a galaxy by galaxy basis, and a factor to scale the total amount of dark matter to the total galaxy mass on a case by case basis, with a basically fixed and well-motivated formula for the halo and sub-halo shapes, this model it does almost as well at fitting a galactic rotation curve as a much simpler single fixed parameter MOND model with no parameters that vary from galaxy to galaxy, as shown in the figures below from the paper, although eyeballing it (I've seen the MOND fits to the rotation curves of many similar galaxies many times), it doesn't look like quite as tight a fit.

This model can't predict the total mass of the galaxy from the luminous matter distribution in the way that MOND does, without also resorting to the Tully-Fischer relationship to which MOND is equivalent. And, this model doesn't provide any theoretical explanation for the systemic variation in the mass-luminosity ratio from one galaxy to the next that MOND does.

Given the additional two degrees of freedom in this two type bosonic dark matter model, it's Chi-square fit should have a Chi-square fit two better than a MOND fit, which would be very tight indeed, instead of being sightly worse.

This model also, at least point, has been tested in a much narrower domain of applicability than MOND. It has basically only been tested in selected spiral galaxies in the SPARC sample, while MOND has been fit to essentially all galaxies of all shapes from smallest to largest. MOND doesn't work quite right in galaxy clusters, but this model hasn't been tested in galaxy clusters, so it provides nothing to compare to there. And, while simple extensions of MOND have been fit neatly to the cosmic microwave radiation background (CMB), and there are single particle type dark matter models that have been fit to the CMB, I have not yet seen a two particle type dark matter fit to the CMB and I'm not even really sure who that would work when one of the dark matter particle types has a mass that varies by a factor of a million from one galaxy to the next.

This is an improvement over models that took fifteen or so free parameters to fit galactic rotation curves as well as MOND, that I blogged about quite a few years ago, which still wasn't really any more predictive than this model. But, it is also definitely a work in progress that has multiple problems to solve before it is an attractive dark matter particle model that fits all of the data well.

The Paper

The introduction to the paper explains the model more fully:

Observations of galaxy and galaxy cluster rotation curves reveal a striking deviation from classical expectations. Instead of exhibiting a Keplerian decline, the measured velocities remain unexpectedly flat, extending far beyond the visible boundaries of galaxies. This persistent flatness, commonly known as the Rotation Curves (RC) problem, constitutes a critical argument in favor of non-baryonic dark matter (DM). Various theories have been proposed to explain these anomalies. Some authors have suggested modifications to Newtonian gravity, while others advocate for the existence of invisible, non-interacting DM. The early observations of the Coma cluster together with more precise measurements of galaxy RC during the 1970s reinforced the DM hypothesis. Freeman’s model of spherical halos introduced the concept of a linearly increasing mass function, and subsequent studies have mapped DM halos exceeding quantitatively the observable galactic regions. 

The possibility that galactic halos could be composed of bosonic DM has also been investigated in several works. In particular, models incorporating an ultralight axion-like particle have attracted much attention, as they naturally give rise to DM halos modeled as Newtonian Bose-Einstein Condensates. The Scalar Field Dark Matter model, which is consistent with the ΛCDM paradigm, predicts large-scale phenomena that align with linear-order perturbations. By employing ground state solutions of the Schrödinger-Poisson (SP) system—the only stable configuration where all bosonic particles reside in the lowest energy state—these models successfully reproduce the observed RC. Stability analyses further confirm that while the ground state is robust against gravitational perturbations, excited state configurations remain inherently unstable. 

Models in which a bosonic field minimally coupled to gravity acts as a source of DM are directly linked with bosonic stars. These can be primarily classified into scalar boson stars (BS) and Proca stars (PS), which are localized, regular, horizonless solutions modeled by massive, free or self-interacting, complex scalar and vector fields bound by gravity, respectively. Recent advances have expanded this framework to include ProcaHiggs stars (PHS), where complex vectors interact with real scalars to yield richer dynamics. Moreover, investigations into multi-field configurations have led to the development of multi-state boson stars and ℓ-bosonic stars, thereby broadening the spectrum of viable models. 

Ed. Proca theories were initially devised as massive photon theories. They don't actually describe the behavior of photons well, but does provide the propagators for massive spin-1 bosons, which include the W and Z bosons of the Standard Model.

The vector boson dark matter candidate is essentially a sterile Z boson (i.e. one that unlike the Z boson doesn't interact via the weak force) that is 35 orders of magnitude less massive than a Z boson. The scalar bosonic dark matter candidate is a massive spin-0 boson, much like a sterile Higgs boson (i.e. one that doesn't interact via any non-gravitational force), but 21 to 27 orders of magnitude less massive than the Standard Model Higgs boson. The vector dark matter candidate is about 9 to 15 orders of magnitude less massive than the scalar dark matter candidate.

The primary dark matter halo component has to be less massive than the subhalo dark matter component, because the size of the Bose-Einstein condensate boson star distribution of a less massive bosonic dark matter candidate is large enough to extend across the entire galaxy, while the size of the Bose-Einstein condensate boson start distribution of a more massive bosonic dark matter candidate is only large enough to extend across a dark matter subhalo which is much smaller than a galaxy. 

The theoretical feasibility of bosonic stars has been extensively examined, particularly regarding their formation mechanisms, stability conditions, and dynamical behavior. While initially conceptually conceived as static and spherically symmetric objects, modern studies now routinely explore rotating configurations that manifest as axisymmetric, spinning solutions in both scalar and vector forms. Their versatility in emulating a range of astrophysical objects—including neutron stars, black holes, and intermediate-mass bodies—renders them a powerful tool in astrophysical modeling, allowing to explore the effect of purely gravitational entities. 

This paper explores the modeling of galactic DM halos using bosonic fields, extending the study initiated in [68] and addressing two open issues identified in that work. First, the previous analysis changed the properties of the vector field for each galaxy instead of treating it as a single DM candidate; and second, it introduced an additional dark component without a clear physical justification. As in [68] we employ bosonic vector fields coupled to gravity to represent the primary galactic halo, thus enhancing RC fits when combined with ordinary matter contributions. 

A significant modification in the present work, which addresses the first open issue, is that we now fix the vector boson mass to a specific scale relevant to the problem, allowing only for the field frequency to vary, thereby identifying constraints on this parameter. Regarding the second issue, in [68] the extra component was introduced through an ad-hoc mathematical adjustment, lacking physical motivation and coherence across the configurations. 

Here, we provide a physically meaningful explanation by employing a subhalo model consisting of a scalar bosonic field coupled to gravity to represent intermediate galactic structures. An illustration of our model is depicted in Fig. 1. 

It consists of the following components: the luminous matter contribution, represented by a yellow ellipsoid (the galaxy); a quasispherical main halo formed by rotating vector bosonic matter extending beyond the galaxy, shown in dark grey; and a set of spherical subhalos modeled as scalar boson star-like structures, depicted in light grey. As we show in this paper, this model significantly improves the RC fits presented in [68], in addition to provide a physically justified framework for them.

The structure of the paper is as follows: In Section II we introduce the theoretical framework for the bosonic fields we employ in our model, along with key clarifications regarding the rescalings and physical units used. Section III details how the individual contributions to the RC are obtained from both luminous and DM systems. In particular, this section discusses the model for DM subhalos under the assumption that they could be formed by a distribution of boson stars. Next, in Section IV we compare our model predictions with observational data, using the same sample of galaxies employed in [68]. This section also provides a quantitative assessment of our new model against the fits reported in [68]. A discussion of this study is presented in Section V along with our conclusions. Additional information on the equations of motion for the scalar and vector bosonic models is provided in Appendix A.

Are these models converging on the massless spin-2 graviton, with varying energies, as a dark matter particle that is really just a gravitational explanation for dark matter phenomena?

One wonders what a model with a single massive tensor dark matter particle with continuous range of masses from about 10^-26 eV to 10^-10 eV with masses distributed in something like a power law (or just an empirical estimate of the frequency of gravitational waves at each frequency which might have a lumpy and gappy distribution) fitted to the distribution of gravitational wave strengths observed by gravitational wave detectors would look like. This wide variation of graviton mass-energies is natural and expected in a graviton as dark matter candidate model.

A galaxy length wave-length would be something on the order of 10^-24 Hertz (which is basically undetectable with current gravitational wave detectors), while some rare phenomena could generate gravitational waves with much shorter wave lengths as indicated in the chart shown below from Wikipedia:

The sensitivity rang of existing gravitational wave observatories is shown in this chart from Wikipedia:

This would put the stochastic background gravitational wave wavelengths in the same vicinity as the scalar dark matter particles in the paper's model, while the vector dark matter particles would be far, far below the frequencies that existing gravitational wave observatories can detect in a far noisier background.

If the frequency range of gravitational waves has a very low floor value similar to that of the vector dark matter candidate in the paper, and there is a big gap between that floor value and the low frequency stochastic background, however, this could be a reasonable fit to the two type bosonic dark matter model in the paper.

But, Einstein's Field Equations are structured in a manner that does not depict gravitational waves and/or graviton which have mass-energy (but not rest mass) as possible sources on the right hand side in the stress-energy tensor, and also obscures their self-interactions which are hidden within the many non-linear differential equations on the left hand side. 

So, while the cumulative impact of graviton mass-energy and non-perturbative gravitational self-interactions is potentially significant in galaxy scale or larger systems, it is systemically ignored because it is very hard to extract from Einstein's Field Equations and is negligible in the strong field systems relative to first order general relative effects, like those seen in mergers of compact objects like stars and black holes, in inspiraling binary systems, where purely perturbative approximations like the Post-Newtonian approximations work well.

One way to overcome this would be to use a massive graviton model with a range of masses comparable to the range of graviton mass-energies, which have been better developed theoretically, instead, and to consider qualitatively and in order of magnitude quantities, how that model would behave differently if all of the gravitons were traveling at exactly the speed of light, rather than the slightly below the speed of light speed of a true massive graviton with a slight rest mass with that speed itself varying slightly based upon graviton mass.

Deur's gravitational work has used somewhat similar modeling, although using massless scalar gravitons, and ignoring the differences between scalar and tensor fields (which are quite plausibly comparatively small). And, I suspect that Deur's model would closely approximate this massive graviton model (and the real world data). But, I don't have the general relativity and mathematical expertise necessary to test this myself.

Will A Next Generation Collider See A Sphaleron?

Overview

A new pair of preprints, whose abstracts and citations are set forth below, examine the sphaleron energy threshold with newly updated experimental values of Standard Model physical constants and rigorous calculations, and its other properties. This tells experimentalists very specifically where to look and what to look for when trying to observe a Standard Model sphaleron interaction.

The sphaleron interaction is the only time in the Standard Model of Particle Physics that baryon number and lepton number are not simultaneously conserved. 

But it requires extremely high collider energies to form in detectable numers (an order of magnitude greater collider energy than the nominal energy levels is required because the energy of the interaction must be confined so compactly, so a collider energy of something on the order of 91 TeV is needed to confidently assert that they have been discovered).

Not Yet Observed Standard Model Phenomena

The two biggest predictions of the Standard Model of Particle Physics that haven't been observed yet are the sphaleron and the failure to definitively observe pure glueballs (a strong force bound hadron with no quarks) and certain other hadrons predicted to exist in Standard Model quantum chromodynamics (QCD). 

Standard Model Hadron Predictions Not Yet Seen

Current experiments have more than enough energy to produce glueballs, which are predicted to have masses on the order of 0.5 GeV to 3 GeV in their ground states (while the LHC can create energies up to 14,000 GeV), at some experimentally observed mesons have been provisionally identified as likely glueballs. 

But identifying them definitively against other possible explanations of glueball-like resonances is challenging, since they are electromagnetically neutral, color charge neutral, don't interact via the weak force at the tree-level, and are bosons with integer spins shared by mesons in overlapping mass ranges. Glueballs have a natural tendency to blend into mesons with the same quantum numbers, resulting in mixed hadron resonances.

A similar issue applies to some of the heaviest hadrons predicted by the Standard Model but not yet definitively identified with resonances observed at sufficient statistical significance. But the most massive of these have ground states with masses of 20 GeV or less, and a few new ones are identified every year these days. Observing the last few is mostly just a matter of time.

Similarly, the project of identifying the underlying structure of hadron resonances other than simple pseudo-scalar valence quark-antiquark mesons and simple three valence quark baryons, is progressing one hard won resonance identification at a time with no sweeping explanations for large groups of resonances whose structures do not have a consensus explanation. 

There are even hints of exceeding improbable, short lived, and rare ultrahigh energy toponium (i.e. a meson made up of a top quark and anti-top quark with a mass on the order of 340 to 350 GeV), which would also be enhanced at a next generation higher energy particle collider, with a 73 TeV collider energy with a very large number of collisions, being a key threshold to detect this highly improbable resonance. It is rare not just because it takes high energies, but also because of the high risk that the valence top quark and valence anti-top quark necessary to form one would decay or annihilate with each other, before the quarks could hadronize into the most massive theoretically possible simple quark-antiquark meson. Toponium is almost guaranteed to be seen at a next generation collider along the lines of the LHC but more powerful.

Sphalerons

A sphaleron, in contrast, is basically the only major Standard Model prediction that is not yet confirmed, with an energy scale about 730 times that of a Higgs boson, that requires a bigger accelerator to confirm or rule out, even though the nominal sphaleron energy of 9.1 TeV is less than the 14 TeV peak energy of the LHC.

Analysis

To be clear, this study does not alter the long standing conclusion that sphaleron interactions cannot explain the baryon asymmetry of the universe (i.e. the extreme excess of matter over anti-matter in quarks, which is also true of charged leptons), although it does tweak estimates of what percentage of baryon asymmetry this interaction can explain with Standard Model physics.

I put even odds on whether sphalerons actually exist or not. A mathematically consistent modification of the Standard Model that would make baryon number and lepton number conserved symmetries of the Standard Model, which would make sphalerons impossible, would have almost no important phenomenological consequences for anything other than (i) baryogenesis and leptogenesis in the first few seconds after the Big Bang, which we don't really understand yet anyway and which could be explained without any baryon number and lepton number violations in other ways, such as a mirror universe model, and (ii) the presence or absence of sphaleron decay signatures in ultrahigh energy collider experiments. 

Non-detection of sphalerons would also disfavor a wide variety of grand unified theories (GUTs) and Theories of Everything (TOEs), which usually permit violations of baryon number and lepton number, which makes phenomena like proton decay, which is forbidden in the Standard Model of Particle Physics, rare but possible.

But, detecting sphalerons as predicted would also be a triumph for the Standard Model taken to the extremes of its domain of applicability.

The Standard Model prediction is that there would be a desert of new physics (within or beyond the Standard Model) at energies above those where a sphaleron are observed.

The Papers

The electroweak sphaleron is a static, unstable solution of the Standard Model classical field equations, representing the energy barrier between topologically distinct vacua. 

In this work, we present a comprehensive updated analysis of the sphaleron using current Standard Model parameters with the physical Higgs boson mass of m(H)=125.1 GeV and m(W)=80.4 GeV, rather than the m(H)=m(W) approximation common in earlier studies. The study includes: (i) a complete derivation of the SU(2)×U(1) electroweak Lagrangian and field equations without gauge fixing constraints, (ii) high-precision numerical solutions for the static sphaleron configuration yielding a sphaleron energy E(sph)≃9.1 TeV, (iii) an analysis of the minimum energy path in field space connecting the sphaleron to the vacuum (a 1D potential barrier as a function of Chern-Simons number), and (iv) calculation of the sphaleron single unstable mode with negative eigenvalue ω^2=−2.7m(W)^2, providing analytical fits for its eigenfunction. 

We find that using the measured Higgs mass modifies the unstable mode frequency, with important implications for baryon number violation rates in both early universe cosmology and potential high-energy collider signatures. These results provide essential input for accurate lattice simulations of sphaleron transitions and precision calculations of baryon number violation processes.

Konstantin T. Matchev, Sarunas Verner, "The Electroweak Sphaleron Revisited: I. Static Solutions, Energy Barrier, and Unstable Modes" arXiv:2505.05607 (May 8, 2025).

We present a comprehensive analysis of electroweak sphaleron decay dynamics, employing both analytical techniques and high-resolution numerical simulations. 

Using a spherically symmetric ansatz, we reformulate the system as a (1+1)-dimensional problem and analyze its stability properties with current Standard Model parameters (m(H)=125.1 GeV, m(W)=80.4 GeV). We identify precisely one unstable mode with eigenvalue ω^2 ≃ −2.7m(W)^2 and numerically evolve the full non-linear field equations under various initial conditions. Through spectral decomposition, we quantify the particle production resulting from the sphaleron decay. 

Our results demonstrate that the decay process is dominated by transverse gauge bosons, which constitute approximately 80% of the total energy and multiplicity, while Higgs bosons account for only 7-8%. On average, the sphaleron decays into 49 W bosons and 4 Higgs bosons. The particle spectra consistently peak at momenta k ∼ 1−1.5m(W), reflecting the characteristic size of the sphaleron. 

Remarkably, these properties remain robust across different decay scenarios, suggesting that the fundamental structure of the sphaleron, rather than specific triggering mechanisms, determines the decay outcomes. These findings provide distinctive experimental signatures of non-perturbative topological transitions in the electroweak theory, with significant implications for baryon number violation in the early universe and potentially for high-energy collider physics.

Konstantin T. Matchev, Sarunas Verner, "The Electroweak Sphaleron Revisited: II. Study of Decay Dynamics" arXiv:2505.05608 (May 8, 2025).

The Punic People Were Mostly Greek, Not Levantine, In Ancestry

Ancient DNA from the Iron Age and classical Greco-Roman era reveals that the Punic people were much closer genetically to the Greeks and modern Sicilians than to the Phoenicians of the Levant who founded this maritime empire in the Western Mediterranean.

Punic people from this time period had been expected to be genetically similar to the Phoenicians were had often been assumed to be the ancestors of the Punic people, since archaeological and historical information indicated that the Phoenicians founded Carthage and other Punic cities. Linguistic information had also supported this expectation:

The Punic language, also called Phoenicio-Punic or Carthaginian, is an extinct variety of the Phoenician language, a Canaanite language of the Northwest Semitic branch of the Semitic languages. An offshoot of the Phoenician language of coastal West Asia (modern Lebanon and north western Syria), it was principally spoken on the Mediterranean coast of Northwest Africa, the Iberian Peninsula and several Mediterranean islands, such as Malta, Sicily, and Sardinia by the Punic people, or western Phoenicians, throughout classical antiquity, from the 8th century BC to the 6th century AD.

To the extent that the Punic people were genetically different from the Greeks, this was predominantly due to Iberian and Northwest African admixture, rather than due to Levantine admixture. 

Levantine admixture was completely absent from the Punic sample, except in three individuals (about 5% of the Punic sample analysed with Admixture) who were predominantly Levantine, and another four individuals who were predominantly North African in ancestry with very minor Levantine admixture (but with no Greek, Iberian, or other kinds of ancestry). 

This suggests a narrative in which a 95% Greek-like Punic people may have mostly replaced (without meaningful admixing with) a society in which some people with nearly purely Levantine Phoenicians, and some people were assimilated indigenous Northwest Africans with minor Phoenician ancestry.

Likewise, none of the contemporaneous ancient DNA from the Levant showed any Greek admixture at all, although three of eleven samples had small amounts of North African ancestry, and a fourth had small amounts of Iranian and Iberian ancestry (but no North African admixture).

The paper is Harald Ringbauer, et al., "Punic people were genetically diverse with almost no Levantine ancestors" Nature (April 2025).

As Bernard explains at his blog (via Google translate from French):

Phoenician culture emerged in Bronze Age city-states in the Levant. By the early first millennium BCE, the Phoenicians had established an extensive trade network along the Mediterranean coast as far south as the southwest shores of the Iberian Peninsula, spreading their culture, religion, and language. 

By the mid-sixth century BCE, Carthage, a Phoenician colony in present-day Tunisia, emerged as a major center of power in the central and western Mediterranean, as Levantine influence declined as their cities fell under the control of the Neo-Assyrian and Neo-Babylonian empires. Carthage subsequently came into conflict with Greek city-states in the fifth and fourth centuries BCE, and then with the Roman Empire in the third and second centuries BCE, before its final destruction in 146 BCE. 

In this article, the term Punic is given to all archaeological sites in the central and western Mediterranean associated with Phoenician culture, dated between the sixth and second centuries BCE, corresponding to the hegemony of Carthage in the region.

They analyzed the genomes of 210 ancient individuals from 14 Phoenician or Punic archaeological sites located in the Iberian Peninsula, Sardinia, Sicily, North Africa and the Levant dated between 600 and 150 BCE. There are no individuals older than 600 BCE, because before this date cremation was the most common burial method in these communities.

We don't know if the Phoenician founders of Carthage were later replaced by Greeks, if the original Bronze Age Phoenician colonists were recruited from Greece in the first place with a small endogamous caste of Levantine elites leading them, or if they were brought in by the Phoenicians later on as a caste of maritime people subordinate to the Phoenicians who ultimately rose to become the dominant caste in Punic society as the Bronze Age Phoenician maritime empire fell apart.

The ancient DNA samples come almost entirely from the time period at and after the Punic region lost close contact with the Phoenicians of the Levant.

It is possible that Levantine Phoenicians and Greek/North African/Iberian peoples co-existed in the Punic region but were basically genetically distinct endogamous castes, and that the Phoenician ancient DNA from this later period is mostly absent from the sample because Phoenicians continued to cremate their dead, rather than because they had been replaced, while the other caste that had substantially Greek ancestry buried their dead at this point. (The Bronze Age Greeks also mostly cremated their dead at the point in time when Indo-Europeans conquered them and converted them to an Indo-European language.)

This linguistic data can help us weigh which of the possible narratives to explain the ancient DNA is most plausible.

The fact that the Punic people spoke a Phoenician language, rather than Greek or Latin, however, despite their lack of significant Levantine Phoenician genetic ancestry, suggests that the ancestors of the Punic people with Greek ancestry underwent a language shift from Greek to Phoenician due to elite dominance by a Levantine Phoenician elite.  

If ancestors of the genetically Greek Punic people had replaced the Levantine Phoenician people by simply conquering them, we would have expected the Punic people to speak a language related to Greek rather than a North Semitic language (that is a close linguistic cousin of Hebrew and Arabic).

Yet, the lack of admixture between the caste whose members had any Levantine Phoenician ancestry, and the caste that is mostly Greek in genetic ancestry tends to disfavor the presence of the non-Levantine caste in the earliest Bronze Age founding period of Carthage. This inference is particularly strong in light of that fact that the Phoenicians did have some admixture with the indigenous North Africans who proceeded them in Carthage and the vicinity.

It is more plausible that the primarily Greek caste became part of Punic society in the roughly two and a half entry long time period from the mid-sixth century BCE, when Levantine influence declined as their cities fell under the control of the Neo-Assyrian and Neo-Babylonian empires, to the fifth and fourth centuries BCE, when Carthage subsequently came into conflict with Greek city-states. 

Before that, these Phoenician colonies were probably just Levantine Phoenicians and indigenous North Africans. It also seems likely that this demographic shift took place at the early end of this quarter millennium time period, allowing the dominant-subordinate status of the respective castes to emerge before the conflicts with the Greek city-states reached their high water mark.

Another possibility is that part of what keep a Levantine Phoenician caste distinct and endogamous from a caste with an ancestral Greek core, is that the Levantine Phoenician caste spoke Punic, while the caste with an ancestral Greek core spoke some dialect of Greek as their primary language, but didn't interact with the outside world much because the Levantine Phoenicians were the ruling caste of the Punic world, even though they made up only a modest percentage of the total population. 

This would have some similarities to the situation in medieval Finland while it was under Swedish rule, where power was held by Swedish speakers for centuries, even though most of the people spoke Finnish as their primary language, but with less genetic admixture between the two linguistic groups.

Early Homo Erectus In Spain And Where It Fits In The Larger Narrative

Overview

Anthropologists have found partial Homo erectus remains in Spain from 1.1-1.4 million years ago, adding to 1.97 million year old Homo erectus remains in Grăunceanu, Romania, and 1.77-1.85 million year old Homo erectus remains in Dmanisi, Georgia. 

Homo erectus first appears in Africa. Outside of Africa, Homo erectus remains are most often found in Indonesia and China, dating from around 108,000 years ago in Southeast Asia, back to about 70,000 years after this species evolved in Africa. 

Homo erectus went extinct in most of the world around 1,000,000 years ago, but persisted longer in Southeast Asia and possibly in East Asia, and relict populations of Homo erectus probably admixed with Denisovans at some point when both species existed. A major population bottleneck described below, probably took place in Homo erectus starting around 930,000 years ago, but it didn't result in the complete extinction of the species. Homo erectus was probably extinct by the time that modern humans first ventured beyond South Asia (not long after the Toba eruption ca. 75,000 years ago). It is plausible that the Toba eruption, followed by first contact with modern humans, may have led to the final extinction of Homo erectus, to the final extinction of H. floresiensis and H. luzonensis, and also to the extinction of Denisovans over most of their range (with the last relict Denisovans in Tibet probably going extinct in connection with their contacts with modern humans in this remote place).

We know that Homo erectus evolved in Africa rather than Eurasia, because that is where the species that Homo erectus evolved from, mostly likely H. habilis, but possibly some other African archaic hominin, was located at the time, and not just because the oldest Homo erectus remains are found there.

The oldest identified H. erectus specimen is a 2.04 million year old skull, DNH 143, from Drimolen, South Africa, coexisting with the australopithecine Paranthropus robustus. H. erectus dispersed out of Africa soon after evolution, the earliest recorded instances being H. e. georgicus 1.85 to 1.78 million years ago in Georgia and the Indonesian Mojokerto and Sangiran sites 1.8 to 1.6 million years ago.

(The quoted Wikipedia summary hasn't been updated to reflect the Romanian discovery announced earlier this year.)

Half a million years and a few hundred meters away from this site, there are Homo antecessor remains, from a time when Homo erectus had gone extinct in Europe, almost 700,000 years before Homo erectus went extinct in Asia.

The New Discovery

ATE7-1 fossil face (right) with mirrored 3D model (left). Credit: Maria D. Guillén / IPHES-CERCA / Elena Santos / CENIEH

When the global timeline passed one million years ago, more than half the span of hominin presence in Eurasia had already passed by. The earliest archaeological evidence in Eurasia is more than two million years old—found in places like Shangchen, China, and the Dawqara Formation of Jordan. Just this year Grăunceanu, Romania, joined the list of early archaeological traces of hominins in Europe, dating to an estimated 1.97 million years ago.

Still, I think about the threshold of one million years ago quite often. The number of sites in Eurasia with hominin evidence before one million years ago has grown quite large. It would have been hard to imagine this in 1990, when many scientists wondered if any sites in Eurasia were really older than this. Today there are many. And yet, the number of sites with fossils of hominins is quite a lot smaller than the number with stone artifacts or cutmarked animal bones. Most are in China or Indonesia, in addition to the exceptional site of Dmanisi, Georgia.

In western Europe there may be only two such sites, both in Spain: Sima del Elefante and Barranco Léon.

This week Rosa Huguet and collaborators have reported on a significant new addition to this very humble record. In work at Sima del Elefante in 2022, excavators uncovered a fragmentary facial skeleton, designated as ATE7-1. The estimated age of this fossil face is between 1.4 million and 1.1 million years ago. The new fossil joins two other hominin fossils from this cave deposit, within the same range of ages, a finger bone and a fragment of the front portion of a mandible with several worn teeth, ATE9-1. These fossils have been previously published, the mandible in 2008.

None of these fossils provide much to go on. Huguet and coworkers compared the facial anatomy of ATE7-1 with fossil faces attributed to Homo erectus from Dmanisi, Georgia, and Sangiran, Indonesia. They also compared the face to fossils from Gran Dolina, Spain, attributed to Homo antecessor. This site is located only a few hundred meters from Sima del Elefante but represents hominins and stone artifacts from around 780,000 years ago—as much as a half million years or more later than Sima del Elefante.

The ATE7-1 face is more like most H. erectus faces than either is like the later Gran Dolina fossils.

From John Hawks.

Context

Where does this discovery fit in the larger narrative of archaic hominin evolution?

Neanderthals, Denisovans, and modern humans (i.e. Homo sapiens) all share a Homo erectus ancestor and probably also at least one intermediate archaic hominin ancestor that evolved from Homo erectus.

The oldest archaeological evidence of modern humans, which is, order of magnitude consistent with age estimates for the most recent common ancestor of all modern human uniparental Y-DNA and mtDNA lineages, is about 300,000 years ago in Africa. Modern humans first left Africa around 125,000 to 100,000 years ago, and did so via the Middle East rather than Iberia. But the lion's share of non-African modern humans appear to be descended from a later wave of modern human expansion out of Africa about 50,000-74,000 years ago, with the lion's share of that wave closer to 50,000 years ago than 74,000 years ago. Neanderthal populations largely stalled this expansion into Europe until about 40,000 years ago. One or more of the hominin populations of Southeast Asia, and the jungles of Southeast Asia, probably stalled modern human expansion via the Southern route into Asia until around the time of the Toba eruption around 74,000 years ago (with the eruption possibly weakening these barriers and possibly also creating a reason for the modern humans of South Asia to expand to the Southeast).

The oldest Neanderthal remains are about 430,000 years old. Neanderthals were moribund by 40,000 years ago (with modern human Cro-Magnon people entering Europe around the same time that Neanderthals became extinct and overlapping with them for periods of a thousand or two thousand years or so in any one place), with the final relict population going extinct around 29,000 years ago. The leading explanations for Neanderthal extinction include a wave of volcanic eruptions, climate change, and the growing superiority of modern human hunter-gatherers due to their cultural evolution (e.g. stone technologies and the domestication of dogs) and/or genetic evolution. The range of Neanderthals extended from Northern Wales to the Middle East to South Asia and the Altai Mountains. There was significant Neanderthal admixture with modern humans, probably around 50,000-100,000 years ago (the latest estimates tend to favor a more recent date) in the vicinity of the Middle East or Iran (leaving a DNA legacy in all non-African modern humans), and there was also a more modern admixture with Altai Neanderthals (leaving a DNA legacy in Asian modern humans). Non-Africans today have up to 2% Neanderthal DNA, with Asians having a little more than Europeans, although ancient DNA from modern humans in ancient Eurasia, much closer to Neanderthal admixture sometimes have higher percentages of Neanderthal admixture. Neanderthals had bigger brains than modern humans, but also a more static material culture and less diverse range of hunting prey heavily concentrated around large megafauna (suggesting reduced brain plasticity and less ability to adapt culturally rather than genetically), with modern humans also relied on a wider array of smaller prey like rabbits, smaller birds, fish, and other seafood. At the time of first contact with modern humans, the effective population size of Neanderthals was about ten times smaller than the effective population size of modern human Cro-Magnons, and the effective Neanderthal effective population size ranged from about 3,000-12,000 throughout their existence and was fractured into multiple more or less isolated regional subpopulations.

Wikipedia says this about the extinction of Neanderthals:

The extinction of Neanderthals was part of the broader Late Pleistocene megafaunal extinction event. Neanderthals were replaced by modern humans, indicated by the near-complete replacement of Middle Palaeolithic Mousterian stone technology with modern human Upper Palaeolithic Aurignacian stone technology across Europe (the Middle-to-Upper Palaeolithic Transition) from 41,000 to 39,000 years ago. Iberian Neanderthals possibly persisted until about 35,000 years ago, modern human expansion perhaps impeded by the Ebro River. Neanderthals in Gibraltar may have survived as late as 28,000 years ago at Gorham's Cave. The dating of these late Iberian sites is contested.

Historically, the cause of extinction of Neanderthals and other archaic humans was viewed under an imperialistic guise, with the superior invading modern humans exterminating and replacing the inferior species.

When sapiens began to expand and spread, he eliminated the other contemporary races [including Neanderthals] just as the white man drove out the Australian aborigines and the North American Indians.

— Ernst Mayr, 1950

The assimilation of Neanderthal populations into modern human populations had long been hypothesised with supposed hybrid specimens, and was revitalised with the discovery of archaic human DNA in modern humans. Similarly, the Châtelperronian industry of central France and northern Spain may represent a culture of Neanderthals adopting modern human techniques, via acculturation. Other ambiguous transitional cultures include the Italian Uluzzian industry, and the Balkan Szeletian industry.

Aside from competition with modern humans, Neanderthal extinction has also been ascribed to their low population as well as the resulting mutational meltdown, making them less adaptable to major environmental changes (specifically Heinrich event 4) or new diseases.

The admixture between modern humans and Neanderthals went in both directions. And, some of the late archaeological tool cultures of Neanderthal, which coincide with the arrive of modern humans in Europe, may reflect the increased brain plasticity of hybrid Neanderthal-modern human individuals.

Denisovans (named after the cave in the Altai where the type remains were discovered) probably existed from at least 285,000 years ago to about 25,000 years ago, general in Asia to the east of the Neanderthal range from Altai and Tibet to Southeast Asia, and overlapping with the Neanderthal range in the Altai region. High altitude adaptation DNA admixed from Denisovans are found in Tibetans. Trace levels of Denisovan admixture are found in mainland Southeast Asia and East Asia, and in island Southeast Asia up to the Wallace Line. Modern humans with Australian aboriginal ancestry or Papuan ancestry or Filipino negrito ancestry have substantial Denisovan ancestry (up to 6%) in addition to their Neanderthal ancestry (up to 2%). Presumably, the Denisovan-modern human admixture whose legacies exist in Australian aborigines, Papuans, Filipino negritos, and mainland Southeast Asians and East Asians must have occurred around the time of first contact between the first wave of modern humans in Asia around 50,000 to 75,000 years ago, and was then greatly diluted by subsequent waves of modern human migration west of the Wallace line in Asia. Also, Denisovans presumably went extinct within a thousand or two thousand years or so of first contact with modern humans (which took place much later in Tibet than almost everywhere else).

The exact path from Homo erectus to modern humans, Neanderthals, and Denisovans (and possibly other now extinct archaic species derived from Homo erectus) is a matter of ongoing investigation and debate.

Denisovan mtDNA diverged from that of modern humans and Neanderthals about 1,313,500–779,300 years ago; whereas modern human and Neanderthal mtDNA diverged 618,000–321,200 years ago. Krause and colleagues then concluded that Denisovans were the descendants of an earlier migration of H. erectus out of Africa, completely distinct from modern humans and Neanderthals.

However, according to the nuclear DNA (nDNA) of Denisova 3—which had an unusual degree of DNA preservation with only low-level contamination—Denisovans and Neanderthals were more closely related to each other than they were to modern humans. Using the percent distance from human–chimpanzee last common ancestor, Denisovans/Neanderthals split from modern humans about 804,000 years ago, and from each other 640,000 years ago. 

Using a mutation rate of 1×10^−9 or 0.5×10^−9 per base pair (bp) per year, the Neanderthal/Denisovan split occurred around either 236–190,000 or 473–381,000 years ago respectively. Using 1.1×10^−8 per generation with a new generation every 29 years, the time is 744,000 years ago. Using 5×10^−10 nucleotide site per year, it is 616,000 years ago. Using the latter dates, the split had likely already occurred by the time hominins spread out across Europe. 

H. heidelbergensis is typically considered to have been the direct ancestor of Denisovans and Neanderthals, and sometimes also modern humans. Due to the strong divergence in dental anatomy, they [i.e. Denisovans] may have split before characteristic Neanderthal dentition evolved about 300,000 years ago.

The more divergent Denisovan mtDNA has been interpreted as evidence of admixture between Denisovans and an unknown archaic human population, possibly a relict H. erectus or H. erectus-like population about 53,000 years ago. Alternatively, divergent mtDNA could have also resulted from the persistence of an ancient mtDNA lineage which only went extinct in modern humans and Neanderthals through genetic drift. Modern humans contributed mtDNA to the Neanderthal lineage, but not to the Denisovan mitochondrial genomes yet sequenced. The mtDNA sequence from the femur of a 400,000-year-old H. heidelbergensis from the Sima de los Huesos Cave in Spain was found to be related to those of Neanderthals and Denisovans, but closer to Denisovans, and the authors posited that this mtDNA represents an archaic sequence which was subsequently lost in Neanderthals due to replacement by a modern-human-related sequence.

The intermediate species that is the most recent common ancestor of Neanderthals, Denisovans, and modern humans probably arose not long after a genetic bottleneck which has been inferred from modern DNA. This genetic bottleneck probably occurred in the clade of H. erectus which is ancestral to modern humans. As one secondary source explaining this notes:

Between 930,000 and 813,000 years ago, something nearly ended humanity before it even began. A mysterious bottleneck reduced the human breeding population to just 1,280 individuals, pushing our ancestors to the brink of extinction for an astonishing 117,000 years. 

Scientists have long puzzled over a gap in the African and Eurasian fossil records, and now, a team of researchers may have found the answer. Using a groundbreaking method called FitCoal, they analyzed the genomes of 3,154 modern humans to reconstruct ancient population sizes. What they found was staggering. Nearly 99% of early humans vanished, likely due to extreme climate events such as glaciations, severe droughts, and the collapse of ecosystems.

The world was changing. Glaciation, extreme droughts, and collapsing ecosystems made survival nearly impossible. Food sources vanished, and so did most of our ancestors. Those who remained – just a tiny fraction of the original population – fought to endure in a harsh and unpredictable environment. 

But against all odds, they survived. And in doing so, they may have changed the course of human evolution forever. Scientists believe this bottleneck could have led to the merging of two ancestral chromosomes, forming what we now know as chromosome 2 – a key feature that separates modern humans from other primates.

Around 813,000 years ago, the climate began to shift. Our ancestors may have mastered fire, allowing them to cook food, stay warm, and fend off predators. Populations rebounded, and from that tiny group of survivors, the future of humanity was born. 

This discovery reshapes our understanding of human history, and raises new questions. Where did these survivors live? How did they overcome such extreme conditions? Did this struggle push human intelligence to evolve faster?

The paper that is the basis for this account is Wangjie Hu, et al., "Genomic inference of a severe human bottleneck during the Early to Middle Pleistocene transition" 381(6661) Science 979-984 (August 31, 2023). Its abstract materials state:

Editor’s summary 

Today, there are more than 8 billion human beings on the planet. We dominate Earth’s landscapes, and our activities are driving large numbers of other species to extinction. Had a researcher looked at the world sometime between 800,000 and 900,000 years ago, however, the picture would have been quite different. Hu et al. used a newly developed coalescent model to predict past human population sizes from more than 3000 present-day human genomes (see the Perspective by Ashton and Stringer). The model detected a reduction in the population size of our ancestors from about 100,000 to about 1000 individuals, which persisted for about 100,000 years. The decline appears to have coincided with both major climate change and subsequent speciation events. —Sacha Vignieri 

Abstract 

Population size history is essential for studying human evolution. However, ancient population size history during the Pleistocene is notoriously difficult to unravel. In this study, we developed a fast infinitesimal time coalescent process (FitCoal) to circumvent this difficulty and calculated the composite likelihood for present-day human genomic sequences of 3154 individuals. Results showed that human ancestors went through a severe population bottleneck with about 1280 breeding individuals between around 930,000 and 813,000 years ago. The bottleneck lasted for about 117,000 years and brought human ancestors close to extinction. This bottleneck is congruent with a substantial chronological gap in the available African and Eurasian fossil record. Our results provide new insights into our ancestry and suggest a coincident speciation event.

The proposed climate event was part of the Mid-Pleistocene Transition. Some key aspects of this, in places where Homo erectus reached, were as follows:

Europe

In Europe, the MPT was associated with the Epivillafranchian-Galerian transition and may have led to the local extinction of, among other taxa, Puma pardoides, Megantereon whitei, and Xenocyon lycaonoides. The prevalence of ungulates adapted for grazing increased in the Mediterranean region after the "0.9 Ma event". The northern North Sea Basin was first glaciated during the MPT. The increased intensity of transgressive-regressive cycles is recorded in northern Italy.

Asia

The cooling brought about by the MPT increased westerly aridity in the western Tarim Basin. East Asian Summer Monsoon (EASM) precipitation declined. Grasslands expanded across the North China Plain as forests contracted.

During the MPT, the Indian Summer Monsoon (ISM) decreased in strength. In the middle of the MPT, there was a sudden decrease in denitrification, likely due to increased solubility of oxygen during lengthened glacial periods. After the MPT, the Bay of Bengal experienced increased stratification as a result of the strengthening of the ISM, which resulted in increased riverine flux, inhibiting mixing and creating a shallow thermocline, with stratification being stronger during interstadials than stadials. Paradoxically, variability in Δδ18O in the Bay of Bengal between glacials and interglacials decreased following the MPT.

Africa

In Central Africa, detectable floral changes corresponding to glacial cycles were absent prior to the MPT. Following the MPT, a clear cyclicity became evident, with interglacials being characterised by warm and dry conditions while glacials were cool and humid.

According to one of the leading papers on the 0.9 Ma Event, closely associated with the Homo erectus genetic bottleneck:

The Early-Middle Pleistocene Transition (EMPT) (ca. 1.4–0.4 Ma) represents a fundamental transformation in the Earth's climate state, starting at 1.4 Ma with a progressive increase in the amplitude of climatic oscillations and the establishment of strong asymmetry in global ice volume cycles. The progressive shift from a 41kyr–100kyr orbital rhythm was followed by the first major build-up of global ice volume during MIS 24-22, the so-called “0.9 Ma event”. The Vallparadís Section (Vallès-Penedès Basin, NE Iberian Peninsula) is one of the few Pleistocene series in Europe that spans the onset of the transition (from 1.2 to 0.6 Ma), thus representing a pivotal array of localities to investigate the effect of glacial dynamics on environmental conditions in Southern Europe. Here we inspect the effects of the EMPT on terrestrial ecosystems by examining the dietary adaptations (through dental meso- and microwear patterns) of fossil ungulates from the Vallparadís Section dated before and after the “0.9 Ma event”. Results show a steady presence of open grasslands before MIS 22 and more humid conditions at MIS 21. Both before and after MIS 22, a consistent presence of ungulates with long-term patterns that point to a grazing or grass-rich mixed feeding behaviour is observed, while noticeably, short-term patterns point to increased seasonality right after the “0.9 Ma event” glacial period. This increment of seasonality may have had an important effect on the Mediterranean habitats leading to recurring changes in the quality of plant resources available to large herbivores, which in response periodically adopted more mixed feeding behaviours widening their dietary breadth to consume also sub-optimal food items during adverse seasons.

In particular, during this event, global ice volumes increased substantially, and the Northern Hemisphere experienced increased seasonality and aridity, and surface sea temperatures in the North Atlantic reached their lowest values during the EMPT at this time. Also, grasslands expanded across the North China Plain as forests contracted.

This hypothesis is model dependent, could be impacted by sources of systemic error, like the possible much later extinction of Homo erectus populations derived from the same source population, later hard genetic sweeps of Homo erectus source genes, the effective extinction of modern humans arising from other clades of Homo erectus at some much later time, a lack of consideration of Neanderthal or Denisovan genes in the analysis, and a complete lack of ancient Homo erectus genomes. 

Also, in understanding this narrative one has to recognize that genetics researchers call an "effective population" of 1,280 individuals could have involved a census population at any one time that was many times larger than that. And, this is still about five times as large as the effective population size of the founding population of the Americas, for example. So, the bottleneck wasn't quite as extreme as some popular accounts of it would imply.

But the oldest examples of the species Homo antecessor does first appear in Europe, shortly after this inferred bottleneck, and there are no Homo erectus remains in Europe during or after the time of this inferred bottleneck.

Homo antecessor (Latin "pioneer man") is an extinct species of archaic human recorded in the Spanish Sierra de Atapuerca, a productive archaeological site, from 1.2 to 0.8 million years ago during the Early Pleistocene. Populations of this species may have been present elsewhere in Western Europe, and were among the first to settle that region of the world, hence the name. The first fossils were found in the Gran Dolina cave in 1994, and the species was formally described in 1997 as the last common ancestor of modern humans and Neanderthals, supplanting the more conventional H. heidelbergensis in this position. H. antecessor has since been reinterpreted as an offshoot from the modern human line, although probably one branching off just before the modern human/Neanderthal split.

Despite being so ancient, the face is unexpectedly similar to that of modern humans rather than other archaic humans—namely in its overall flatness as well as the curving of the cheekbone as it merges into the upper jaw—although these elements are known only from a juvenile specimen. Brain volume could have been 1,000 cc (61 cu in) or more, but no intact braincase has been discovered. This is within the range of variation for modern humans. Stature estimates range from 162.3–186.8 cm (5 ft 4 in – 6 ft 2 in). H. antecessor may have been broad-chested and rather heavy, much like Neanderthals, although the limbs were proportionally long, a trait more frequent in tropical populations. The kneecaps are thin and have poorly developed tendon attachments. The feet indicate H. antecessor walked differently than modern humans.

H. antecessor was predominantly manufacturing simple pebble and flake stone tools out of quartz and chert, although they used a variety of materials. This industry has some similarities with the more complex Acheulean, an industry which is characteristic of contemporary African and later European sites. Groups may have been dispatching hunting parties, which mainly targeted deer in their savannah and mixed woodland environment. Many of the H. antecessor specimens were cannibalised, perhaps as a cultural practice. There is no evidence they were using fire, and they similarly only inhabited inland Iberia during warm periods, presumably retreating to the coast otherwise.

Meanwhile:

Homo heidelbergensis (also H. erectus heidelbergensis, H. sapiens heidelbergensis) is an extinct species or subspecies of archaic human which existed from around 600,000 to 300,000 years ago, during the Middle Pleistocene. Homo heidelbergensis was widely considered the most recent common ancestor of modern humans and Neanderthals, but this view has been increasingly disputed since the late 2010s.

In the Middle Pleistocene, brain size and height were comparable to modern humans. Like Neanderthals, H. heidelbergensis had a wide chest and robust frame.

Fire likely became an integral part of daily life after 400,000 years ago, and this roughly coincides with more permanent and widespread occupation of Europe (above 45°N), and the appearance of hafting technology to create spears. H. heidelbergensis may have been able to carry out coordinated hunting strategies, and consequently they seem to have had a higher consumption of meat.

It is debated whether or not to constrain H. heidelbergensis to only Europe or to also include African and Asian specimens, and this is further confounded by the type specimen (Mauer 1) being a jawbone, because jawbones feature few diagnostic traits and are generally missing among Middle Pleistocene specimens.

H. heidelbergensis was subsumed in 1950 as a subspecies of H. erectus but today it is more widely classified as its own species. H. heidelbergensis is regarded as a chronospecies, evolving from an African form of H. erectus (sometimes called H. ergaster).

At least three other archaic hominin species overlapped with hominins from the H. erectus era or later.

• Homo floresiensis – Extinct small human species found in Flores
• Homo luzonensis – Archaic human from Luzon, Philippines
• Homo naledi – South African archaic human species

H. floresiensis and H. luzonensis may have been regional variations of the same species and show similarities with each other. The most plausible theory of their phylogenetic position, in my view, is that both of them were sub-species of H. habilis, and may have left Africa, either independently, or together with either H. erectus, the Denisovan ancestor, or Denisovans themselves. H. floresiensis and Denisovans (and possibly the earliest modern humans to arrive there as well) may have co-existed on the island of Flores, Indonesia (which is past the Wallace line) at some point in  time. There are no remains of H. floresiensis, H. luzonensis, H. habilis, or any other archaic hominins before H. erectus disperses from Africa. 

H. naledi was a South African archaic hominin species that flourished from 335,000 to 226,000 years ago, that was probably not directly ancestral to modern humans or any other non-African archaic hominins, but would have co-existed in time (and possibly space) with the earliest modern humans in Africa.

A November 6, 2024 post at this blog recapped some other possible non-African archaic hominins who existed at the same time that modern humans did: 

Notably the remains of the Red Deer Cave People of China from 14,000 years ago (a few thousand years before the start of the Holocene era) are genetically modern humans and are not archaic hominins despite some of their seemingly archaic features. See also here.

I am also inclined to think that they may yet be a small relict population of small archaic hominins in a remote Indonesian jungle on the island of Sumatra and perhaps Flores as well, where these cryptids, called Orang Pendek, locally, have been attested but not definitively confirmed to still exist. I discuss this further at this post.

Homo floresiensis (discovered in 2003) are commonly known as "hobbits" and have been found on the island of Flores. Their phylogeny is disputed, but I find the theory that they are an asian branch of H. habilis to be most convincing. H. luzonesis (discovered in 2007) is similar and contemporaneous, but found further east in the Philippines and is supported by a less complete archaeological record. Both of these diminutive species are found in association with late Pleistocene tools and "oriental fauna".

Personally, being more of a lumper than a splitter, I'm inclined to see H. floresiensis and H. luzonesis as sub-species variations of the same species ("race" within that species to use some outdated terminology), and likewise to see H. longi, H. juluensis, and Denisovans as sub-species variations of the Denisovan species. The Hualongdong archaic hominin fossils ... could be a hybrid individual, perhaps a Neanderthal-Denisovan hybrid individual (something that has precedent in a Denisovan cave DNA sample).

Academic anthropologists, in contrast, tend to be splitters, in part, because it is cool and career advancing to discover and name your own archaic species, in part because the data is so fragmentary that grouping different fragmentary remains in a clade presumes relationships between the remains that aren't solidly proven, and in part, because it is easy to underestimate how much morphological diversity is possible within a single species if populations of it exposed to different environmental conditions.

H. longi a.ka. "dragon man" dates to an earlier time period (still contemporaneous with modern humans in Africa) in China and Manchuria, was discovered in 1933, and has been hypothesized to be a sister clade to Neanderthals, Denisovans, and modern humans, and a descendant of the pre-modern human hominin species H. antecessor due in part to basal archaic features in the skull.

H. juluensis (literally "big heads") is contemporaneous H. longi, and beyond that time frame into the time frame of H. floresiensis and was discovered from 1976-1979 in China and Tibet. The authors assign this specimen along with Xiahe and Penghu fossils, to the Denisovan species (a sister clade to Neanderthals and modern humans) based upon comparisons of their fossil teeth and rough geographic proximity. H. juluensis is found in association with early Paleolithic tools and remains of Paleoarctic fauna. But they have larger brain cases than H. longi. A previous suggestions of the link between H. longi and the Denisovan species are discussed here and here at this blog. At least one Denisovan tooth has been found in Laos dated to 131,000 years ago.

The article also discusses the Hualongdong archaic hominin fossils that "date to the late Middle Pleistocene (~300,000 years BP) and display a mosaic of characteristics that cannot be easily fitted into any one lineage," although they are closer to H. longi and H. juluensis. This individual could be a hybrid between these two subspecies, with H. erectus, or with a Neanderthal who was far east of his usual range.

Prior to 2021, H. longi and H. juluensis tended to be classified as H. erectus (remains of which start to appear at a much greater time depth in Asia) or as archaic modern humans.

The Narmada and Maba partial skulls, especially the latter, are suggestively associated with Neanderthals by the article.

These Asian archaic species also overlap in time with the Southern African archaic hominin clade H. naledi which is a sister clade to the modern human ancestors and to the common ancestor of modern humans, Neanderthals, and Denisovans, but is not actually among our ancestors. As I explained at the link, this species "is basically a story from The Silmarillion of hominin evolution. It is entertaining, especially for hard core human evolution fans, but it doesn't really advance the plot."

A small number of papers reported genetic evidence in modern Africans of admixture with an archaic hominin "ghost species" in Africa, but subsequent papers have explained this "ghost species" signal as a methodological artifact that merely arises from population structure in early modern human Africans (see also here). But there may have been relict archaic hominins that did not admix with modern humans in Africa that were also contemporaneous with modern humans, at least, early on.

The question of whether behaviorally modern humans started showing advanced behavior around 70,000-50,000 years ago (at the dawn of the Upper Paleolithic era and close in time to the Out of Africa event for modern humans), was associated with an evolutionary leap in their brains is an open and unresolved question. See also here (addressing the question of what made modern humans genetically distinct from archaic hominins).