Razib Khan On Our Current Understanding Of Human Evolution

Razib Khan's latest piece on human evolution in his Unsupervised Learning series takes a step back and looks at how the big picture has changed with new discoveries made in the last several decades.

His main point is that archaic hominin introgression may have originally been a much higher percentage of ancestry, with most archaic hominin introgression expelled in the roughly 1,000 years after the initial introgression due to natural selection and incompatibilities between archaic hominin sourced genes and modern human genes. I suspect that the 10%-20% percentage that he cites is quite a bit too high, but surely this did happen to some extent.

As usual, he educated synthesis of the research and evidence is pretty solid, even if not every assertion he makes in laying out a single coherent narrative (like the Population A and Population B that hybridize to form modern humans, with Neanderthals, Denisovans, and "ghost African" populations all derived from Population A hypothesis in the diagram below) has reached the level of academic consensus yet, and even if there is some room to quibble over fine details.

Some highlights of his piece (but please, click on the link and read the whole thing) are quoted below:

A generation ago, we imagined that Homo sapiens, “thinking man,” emerged fully formed in Africa over 100,000 years ago and swept away all our monstrous kin before us through dint of our sheer genius. Today, it seems more likely that it was we who were the monsters out of the dark, the demons about which Neanderthal mothers would tell their little-ones.

In 2002’s The Dawn of Human Culture, Stanford paleoanthropologist Richard Klein presented what at that time was the standard model of the recent origins of humanity. Some time before 50,000 years ago, a new form of human arose through some sort of mutational jump. Klein posited that our genius, our superiority, was because of a macromutation that enabled us to generate fully articulate language. Before the emergence of this new species of human, there were many varieties of human, or, more precisely, hominin. Neanderthals in Europe and Central Asia, various “archaic” lineages in eastern Eurasia, and also descendants of other Homo forms in Africa. 

Ω humans, whom many popular slogans would refer to as “Africans,” rapidly swept away all these varieties of humanity after 50,000 years.

And so it was for a decade. There were dissents; in 2006 Jeffrey Wall and Michael Hammer published Archaic admixture in the human genome. This paper reflected suspicion among many evolutionary geneticists that the orthodoxy promulgated was too pat and simplistic (see also Magnus Nordborg’s 1998 On the Probability of Neanderthal Ancestry). But‌ despite an underground counter-consensus, very few evolutionary geneticists were vocal on this issue in public. . . . This all changed in 2010, when Svante Paabo and colleagues reported that Neanderthal whole genomes yielded strong evidence of several percent admixture into non-Africans, as well as the discovery of a new human lineage in eastern Eurasia, the Denisovans, who also contributed about 5% of the ancestry of Papuans.

Previous work had almost entirely been a matter of inference derived from contemporary populations. You looked at genetic variation in people alive today and worked backward to plausible models of how that variation could have arisen. In the 1980s, geneticists examined mitochondrial lineages, which represent the direct matrilineal genealogy. Geneticists noticed that all non-African populations nested within African genetic variation. They soon replicated this result with the Y chromosome, passed only through males, and the autosomes (markers on chromosomes 1 through 22) representing the whole genetic heritage. These results neatly dovetailed with the findings of paleoanthropologists like Chris Stringer of the British Museum of Natural History, who argued that modern human morphology, mostly exemplified by traits in human skulls, reflected continuity with African Homo, and not Neanderthals. Following the molecular genetic results, researchers applied similar phylogenetic methods to morphometric traits and discovered the same pattern of non-Africans nesting within African variation.

It was an immaculate and tidy story. . . . And that still seems to be much of the story. But not the entire story.

Over the last few years, geneticists have concluded that a much higher fraction of non-African DNA was originally Neanderthal. In an interview with Dwarkesh Patel Harvard’s David Reich asserted that as much as 10-20% of the overall heritage of early non-Africans, just as they were expanding out of the Near East 50,000 years ago, may have been Neanderthal. 

How then is that today we detect only about 2% Neanderthal genes outside of Africa? 

The genome rapidly sheds genetically incompatible segments within a few thousand years via purifying selection. Because Neanderthals diverged from our predominantly African ancestors 600 to 700,000 years ago, their overall genetic makeup exhibited much more striking incompatibilities with the expanding Africans than occurs when different branches of our own species mix (the deepest division in our own lineage dates to about 200,000 years, when Khoisan ancestors diverged from everyone else). No doubt the same phenomenon applied to Denisovan admixture, which today in some Oceanian populations, like those in New Guinea or the indigenous populations of the Philippines, approaches 5% or so.

What does this all mean? 

Because natural selection changes allele frequencies in ways that are out of step with the overall genome, the signatures that we get from modern and ancient DNA are deceptive as to the demographic dynamics of early anatomically modern humans and the Neanderthals (and Denisovans) whom they encountered. All the evidence, both ancient and modern, points to a tiny non-African ancestry population between 50 and 60,000 years ago, a few thousand individuals at most (some models posit a bottleneck of 200 breeding individuals!). If 10-20% of the ancestry of the early modern human expansion, also known as the Initial Upper Paleolithic (IUP), was Neanderthal, that implies the integration of hundreds of Neanderthals, as opposed to ten or twenty.

Did Archaic Ghost Hominins Admix With Humans In Africa?

This article supports the highly plausible theory that all humans share pre-Out of Africa admixture with "ghost" archaic hominin populations, but the methodology used is fairly new and untested.

Admixture between modern humans and extinct hominins has shaped the genomes of present-day individuals, but reconstructing this history has been constrained by the scarcity of archaic samples and unadmixed outgroup populations. 

We introduce TRACE, a reference- and outgroup-free approach that uses features of ancestral recombination graphs to identify archaic ancestry. Simulations show TRACE has high precision and low false discovery rates. 

Applied to 1000 Genomes, TRACE recovers known Neanderthal and Denisovan introgression and uncovers ghost admixture from uncharacterized hominins in both Africans and non-Africans. Ghost ancestry persists in Neanderthal and Denisovan ancestry deserts, challenging their interpretation as Homo sapiens–specific regions. In Oceanians, TRACE finds deep lineages are enriched in Denisovan compared to Neanderthal regions, supporting super-archaic introgression. TRACE enables mapping archaic introgression without archaic genomes.

Yulin Zhang, Arjun Biddanda, Sarah A. Johnson, Colm O’Dushlaine, and Priya Moorjani, "Recovering signatures of archaic hominin introgression using ancestral recombination graphs" Science (July 30, 2026) (open access) DOI: 10.1126/science.aef887

Replicating MOND In A Spin-Foam Model

Spin-foam is a quantum gravity approach that quantizes space-time, rather than treating gravity as a separate force with a carrier boson comparable to a photon or a gluon.

We argue that effects of the quantum spin-connection foam, which describes quantum gravity according to the precanonical quantization of General Relativity, may already be observed in the form of the small cosmological constant and a modification of Newtonian dynamics at small accelerations, manifested in the flat rotation curves of galaxies. 

We obtain a modification of the Newtonian potential that takes into account the existence of a fundamental small acceleration scale, a∗ = 8πGℏϰ, where ϰ is a parameter with the dimensions of inverse spatial volume that appears on dimensional grounds. The connection between ϰ and the hadronic scale of the mass gap in the pure Yang-Mills sector of the Standard Model leads to an estimated value of a∗ compatible with the Milgromian acceleration scale in MOND. The connection between a*^2 and the cosmological constant leads to a realistic value of the latter. Milgromian MOND, together with a theoretically distinct interpolating function, is derived under the assumption that classical dynamics is modified by the mean-field acceleration calculated from the simplest solution of precanonical quantum gravity in the nonrelativistic approximation. 

We also indicate that the effects of Newtonian dynamics modified by the spin-connection foam may be observable in the Solar System and even in laboratory experiments.

Igor V. Kanatchikov, Valery A. Kholodnyi, "Effects of Quantum Spin-Connection Foam in the Solar System, Galaxies, and the Universe" arXiv:2608.12404 (August 11, 2026) (The Seventeenth Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Astrophysics, and Relativistic Field Theories, Pescara 7-12 July 2024, edited by G. Vereshchagin and R. Ruffini, this https URL, October 2026).

Hadronic B Decay Anomalies

The anomaly of the day is an anomaly in a certain kind of B meson decay. I'm very skeptical and think it will go away and is probably due to poor modeling of the Standard Model prediction, but I'll note its existence in this post for further analysis.

The decays B→PP, where the pseudoscalar P is a π or K, have been studied under the assumption of flavour SU(3) symmetry [SU(3)F]. The global fit shows a 3.6σ discrepancy with the Standard Model (SM). 

Separate fits for ΔS=0 and ΔS=1 decays find parameter sets that differ by a factor of 10, suggesting 1000% SU(3)F breaking, significantly larger than the ∼ 30% breaking expected in the SM. This study has been extended to include final states with η and η′ mesons. The resulting global fit, once again under the assumption of SU(3)F symmetry, is worse, with a 4.1σ deviation from the SM. When theoretical constraints |C˜/T˜| = 0.2 or A˜ = 0 are imposed, the fits worsen, with the discrepancy approaching 5σ. These results hint at new-physics contributions to these decays.

Marianne Bouchard, David London, "Anomalies in Hadronic B Decays" arXiv:2608.11298 (August 11, 2026) (Contribution to the Proceedings of the XVI International Conference on Beauty, Charm, Hyperons in Hadronic Interactions (BEACH 2026), 7-12 June 2026, Firenze, Italy).

Another Alternative To Particle Dark Matter

A Covarying Coupling Constant theory performs similarly to, but not better than MOND. Both are much better at explaining galaxy rotation dynamics than a Cold Dark Matter theory using an NFW dark matter distribution (which is theoretically necessary for truly sterile dark matter particles).

The Covarying Coupling Constants (CCC) framework, developed to account for high-redshift JWST observations, contains a mechanism -- a covarying-constant effective mass field keyed to local density -- that modifies galactic dynamics without particle dark matter. 

We test it against the full Spitzer Photometry and Accurate Rotation Curves (SPARC) sample of 175 disc galaxies, extending an earlier study of a few objects. Working in an inverse formulation, in which each model predicts the baryonic rotation curve from the observed one, we compare CCC against Modified Newtonian Dynamics (MOND) and one- and two-parameter Navarro-Frenk-White (NFW) haloes on identical footing, using the reduced χ2ν. We show that the published sharp density turn-off in the earlier study is unphysical and replace it with a smooth transition -- the density-space analogue of the MOND interpolating function, introducing no new parameter. One-parameter smooth-CCC then performs comparably to galaxy-by-galaxy fitted MOND (the lower χ(ν)^2 in 56 per cent of galaxies, mean χ(ν)^2 of 2.58 versus 2.65; the paired difference is not significant), while two-parameter NFW shows a substantially broader fit-quality distribution and a larger tail of poor or boundary-limited fits (mean χ(ν)^2≈7). The CCC turn-off density is not universal (scatter 0.82 dex) and correlates with galaxy size, qualitatively consistent with a spherical reconstruction applied to flattened disc systems. Recast as an acceleration, however, a(t) = V(flat)^2/R(t) has scatter 0.33 dex (on the 91-galaxy resolved subset) -- matching the MOND scale a0 (0.34 dex) -- and comparable magnitude of order 2×10^−10 m/s^2, with its size correlation removed. Though not designed for galactic dynamics, CCC describes rotation curves as well as galaxy-by-galaxy fitted MOND.

Rajendra P. Gupta, Nikolaos Samaras "Testing Covarying Coupling Constants (CCC) against the full SPARC rotation-curve sample: a like-for-like comparison with MOND and NFW" arXiv:2608.11575 (August 12, 2026).

Denisovan Remains May Be Younger Than First Believed

Not long ago, we were finally able to find decent sized bones that proteins provided proteomic evidence (rather than DNA evidence which was not available) were able to match to Denisovans, which were found on the coast of the main island of Taiwan, finally putting a body together with the ghost population implied by DNA evidence. Two more leg bones were recently found.

Earlier dating had suggested an age for the Taiwanese Denisovan remains of about 160,000 years ago, long before modern humans arrived in the region and overlapping with Homo erectus. Analysis of the new leg bones by a more reliable and credible method, however, reveals that they are actually just 45,000 years old, contemporaneous with a modern human presence in the region.

At one level this isn't a surprise. Modern humans in Southeast and East Asia and Oceania have genetic admixture from Denisovans, so they had to overlap at some point. But it is surprising that the two different dating methods differed from each other by a factor of four.

The chemical analysis also suggests that these Denisovans, like Neanderthals, had a diet heavy in meat from large mammals.

My link is to a blog post by John Hawks who cites his sources:

* Chang, Chun-Hsiang, et al., "The first archaic Homo from Taiwan." 6 Nature Communications 6037 (2015). doi:10.1038/ncomms7037

* Grün, R. & Stringer, C., "Direct dating of human fossils and the ever-changing story of human evolution." 322 Quaternary Science Reviews 108379 (2023). https://doi.org/10.1016/j.quascirev.2023.108379

* Kaifu, Y., Chang, et al., "Denisovan leg bones from Taiwan reveal large body size." bioRxiv (2026). https://doi.org/10.64898/2026.08.07.743438

* Tsutaya, et al., "A male Denisovan mandible from Pleistocene Taiwan." 388(6743) Science 176–180 (2025). https://doi.org/10.1126/science.ads3888

* Yoneda, et al., "Habitat and feeding ecology of a Denisovan from Late Pleistocene Taiwan." bioRxiv (2026). https://doi.org/10.64898/2026.08.07.743455

* Zhang, D., et al., "Denisovan DNA in Late Pleistocene sediments from Baishiya Karst Cave on the Tibetan Plateau." 370(6516) Science 584–587 (2020). https://doi.org/10.1126/science.abb6320

Systemic Deviations From The Radial Acceleration Relation?

There is weak evidence that the radial acceleration relation, which is implied by Milgrom's toy-model MOND theory of weak field gravity, requires a single parameter correction is correlated with the compactness of the galaxies measured, primarily in dwarf galaxies.

Query if this could be due to the external field effect or due to gravitationally bound systems that are not in equilibrium? It could also be due to underestimated systemic error in estimating gas fractions, which is much harder to determine that stellar mass.

We ask whether any one-parameter structural correction to the radial acceleration relation (RAR) can be uniquely recovered from SPARC rotation curves, and answer with an identifiability audit: each candidate is benchmarked against per-galaxy nuisance freedom, with predictive scoring against mass-only and data-quality baselines. 

In the full sample (N = 126) the answer is no: a hybrid compactness term improves the fit, but zero-point freedom absorbs the gain, and in cross-validation the model fails to out-predict a mass-only baseline and loses to a quality-flag baseline. 

One regime retains structural information: in gas-dominated, low-acceleration disks -- where MOND's strict locality and ΛCDM feedback models diverge most sharply -- the RAR residual correlates with compactness (r = 0.46, p = 1.3×10^−4), remains significant under hierarchical partial pooling (β = 0.23, p = 1.7×10^−5; N = 63), and survives canonical joint control for quality, sampling, mass, inclination error, and first-order pressure support (r = 0.30, p = 0.02). All significant results pass a Benjamini-Hochberg correction over the declared 27-test family. 

Three limits temper that survival: it is not significant under rank-based control over the widest proxy set; it resides in faint dwarfs independent surveys do not reach; and after mass control it is shared across the mass-size manifold. Pressure support brackets the interpretation -- isotropic drift correction absorbs a quarter of the amplitude, while a Jeans treatment overcorrects resolved cases -- leaving the physical origin undetermined. The audit's product is the extraction limit: claimed corrections must clear the 0.106 dex per-galaxy nuisance floor, a mass-only baseline, and data-quality stratification.

Lukas A. Sosna, "An Identifiability Audit of One-Parameter Structural Corrections to the Radial Acceleration Relation in SPARC" arXiv:2608.08945 (August 9, 2026).

Is Milgrom's Constant Really Constant?

Reductionist physicists always like to derive physical constants, rather than than simply measure them. This paper proposes a way to do so for modified gravity in a MOND-like theory, expanding the theory's domain of applicability to galaxy clusters while sacrificing the universality of Milgrom's constant, a(0). 

It also hints, as Deur explicitly concludes, that MOND-like effects may be influenced by the extent to which a matter distribution is (or is not) spherically symmetric, and provides a mechanism to explain why MOND-like effects arise.

Modified Newtonian Dynamics (MOND) generally resolves the need for dark matter in galaxy rotation curves introducing a single new constant of acceleration a(0). It is well known that increasing a(0) by a factor of a few can alleviate the residual mass discrepancies that MOND leaves in galaxy clusters. 

Within a parameter-free Machian interpretation of MOND, in which a(0) ∼ GM(u)/R(u)^2 arises from the scalar sum of inverse-square distance gravitational mass contributions in the universe, we promote a(0) to a variable influenced by mass external to a locally enclosed region in the spherically symmetric case. 

Instead of a boost of a(0) in terms of gravitational potentials as in EMOND, we show that a boost in terms of this directionless inverse-square field roughly amounts to the boost needed to accommodate the mass discrepancies of MOND in galaxy clusters. We conclude by beginning to generalize the proposed formulation beyond spherical symmetry.

Manuel Uruena Palomo, Juan David Santander, "Machian MOND: a variable a0 in galaxy clusters" arXiv:2608.04894 (August 5, 2026) (published version in International Journal of Modern Physics D).

Cloud-9

A hydrogen gas cloud, called Cloud-9, that has been observed in deep space in the radio wave frequency, which cannot be seen in the visible light spectrum provides a way to distinguish between different dark matter hypotheses and while the paper below doesn't consider it, between modified gravity theories and dark matter hypotheses.

Starless gas clouds provide a new way to test gravitational dynamics and this is just the first examination of many to come.

Between cold dark matter and self-interacting dark matter, the observations strongly favor self-interacting dark matter, although neither hypothesis is a great fit.

Recently, the Five-hundred-meter Aperture Spherical Telescope discovered a gas-rich hydrogen cloud near M94 in the 21cm band. Lacking an optical counterpart, this object, dubbed Cloud-9, has been identified as a compelling Reionization Limited H Cloud (RELHIC). RELHICs provide exceptionally clean laboratories for probing dark matter, free from the baryonic complexities associated with star formation and feedback. 

We show that the observed hydrogen column density profile of Cloud-9 is consistent with a gas cloud embedded in either a cuspy halo predicted by the standard cold dark matter (CDM) model or a cored halo produced by self-interacting dark matter (SIDM). 

In both cases, the halo must have an unusually diffuse central density. The best-fitting CDM halo lies around 7σ below the cosmological concentration--mass relation, whereas SIDM core-forming halos reduce the tension to only around 3σ. 

We further identify Cloud-9 analogs in the Concerto suite of cosmological zoom-in simulations with velocity-dependent SIDM, demonstrating that RELHICs provide a promising new probe of dark matter self-interactions.

Morgan Ohana, Xingyu Zhang, Hai-Bo Yu, "Cold Dark Matter and Self-Interacting Dark Matter Interpretations of Cloud-9" arXiv:2608.04362 (August 5, 2026).

Meanwhile, another new paper finds that the tight relationship between the distribution of baryonic matter and galactic rotation curves has held true for as far back as at least z=0.42 (i.e. 4.4 billion years ago) with astronomy data.

The Baryonic Tully-Fisher relation (BTFR) is one of the tightest scaling relations for disk galaxies in the local Universe, and therefore is an important tool for studying the fomation and evolution of galaxies. . . . 

A random forest classifier is used to investigate the origin of the outlier component. We find that low signal significance and inaccurate inclinations are the key factors that contribute to the outlier population, indicating that observational effects are the dominant origin. 

Evolutionary trends are examined in three different redshift bins. Both the slope and zero point show consistency within 1-σ uncertainty in the two low redshift bins, indicating no significant evolution.

A Possible Glueball Resonance

A glueball is a strong force bound system without any valence quarks that binds gluons, the carrier bosons of the strong force instead of quarks. A well-established resonance seen in experiments at discovery level significance since 2011, whose internal structure is unclear, is shown in a new preprint to be consistent with a nearly pure pseudoscalar glueball state (i.e. a spin-0, electromagnetically neutral boson with odd parity and no valence quarks).

The properties of glueballs (which depend primarily on a single experimentally measured physical constant, the strong force coupling constant), have been calculated from the very early days of quantum chromodynamics (QCD), which is the Standard Model theory of the strong force. And, there are only a modest number of theoretically possible glueballs. This resonance is on the low end of, but consistent with, the mass predicted for a pseudoscalar glueball.

But distinguishing a glueball resonance from a non-glueball resonance is difficult, and because glueballs are always bosons and share quantum numbers with bosons that include valence quarks, they have a natural tendency to blend with similar bosons making a mere glueball component in a resonance rather than a pure glueball, something that is probably common in reality.

There have only been a few resonances that have been convincingly interpreted as a near pure glueball, and this is one of them. But the fact that this is an analysis of a lone author which has not yet been published in a peer reviewed journal bodes caution in accepting this conclusion as definitive. But to the extent that this analysis holds up, it confirms an important qualitative prediction of QCD (i.e. the existence of glueballs with various quantum numbers that have their predicted masses).

In this work, we take the X(2370) with J^PC = 0−+ as a glueball consists of three valence gluons, and construct a six-quark current based on rigorous current-field duality to obtain the glueball-quark Lagrangian. Then we perform Fierz transformation to bosonize the quark current into a series of three pseudoscalar mesons. At last, we obtain ratios among the partial decay widths of the glueball to three pseudoscalar mesons in a model-independent way, which are compatible with the experimental data from the BESIII Collaboration and support assigning the X(2370) as a glueball.

Zhi-Gang Wang, "Analysis of the X(2370) as a glueball based on rigorous current-field duality" arXiv:2608.03362 (August 4, 2026).

In other physics news, the Higgs boson continues to be consistent with Standard Model expectations in newly observed ways.

Sterile Neutrino Parameter Space Further Constrained

Observations of high energy out space sourced neutrinos from an Earth based neutrino detector further constrain the parameter space of possible sterile neutrinos in a way that the LHC, reactor experiments, and an Antarctica based cosmic ray observatory do not.

While the sterile neutrino mass range probed (1-100 TeV) is vastly greater than the active neutrino mass range, this is a sterile neutrino mass range frequently considered in see saw neutrino mass models, so it is relevant for discriminating between hypotheses.

The money chart, below, is a bit difficult to explain, but the key point is that it adds new constraints that rule out sterile neutrinos with certain properties with masses ca. 12-120 TeV, that other experiments can't probe. 

We investigate the sensitivity of the Pierre Auger Observatory to physics beyond the Standard Model arising from magnetic-moment-induced transitions between active and heavy sterile neutrinos. Such dipole portal interactions can enhance neutrino-nucleon cross sections above a kinematic threshold set by the sterile neutrino mass, leading to observable modifications of neutrino detection rates at ultrahigh energies (UHE). 

We estimate the impact of these interactions on both down-going and Earth-skimming neutrino detection channels, the contrasting responses of which enable discrimination between an enhanced neutrino flux and a modified interaction cross section. Using the non-observation of UHE neutrino candidates, we derive neutrino-flux-dependent constraints with 90% confidence-level on the transition magnetic moment for sterile neutrino masses in the range 1 TeV-100 TeV. Under the assumed flux scenarios, the resulting flavor-independent limits extend existing bounds into previously unexplored parameter space.

Pierre Auger Collaboration, "Search for active-sterile neutrino transitions using Pierre Auger Observatory data" arXiv:2608.01496 (August 2, 2026).

A New Higgs Boson Mass Measurement

Every new precision measurement of the Higgs boson mass is golden, and it is increasingly being pinned down to some precision.

A measurement of the Higgs boson mass in the diphoton decay channel is performed using proton-proton collision data at a center-of-mass energy of 13 TeV. The data set recorded with the CMS detector between 2016 and 2018 is used, corresponding to an integrated luminosity of 138 fb−1. A refined detector calibration and new analysis techniques are employed to improve the precision of the results compared to earlier measurements. The Higgs boson mass is measured to be mH = 125.13 ± 0.15 GeV = 125.13 ± 0.10 (stat) ± 0.12 (syst) GeV. 

In addition, a combination with the mass measurement at center-of-mass energies of 7 and 8 TeV in the diphoton final state is performed resulting in mH = 125.06 ± 0.14 GeV = 125.06 ± 0.09 (stat) ± 0.11 (syst) GeV.

CMS Collaboration, "A measurement of the Higgs boson mass in the diphoton decay channel in proton-proton collisions at s√ = 13TeV" arXiv:2607.28396 (July 30, 2026) (Submitted to Physics Letters B.).

This result compares to a Particle Data Group global average of 125.13 ± 0.11 GeV (S = 1.5).

LambdaCMD Still Broken

No matter how much you fuss with the LambdaCDM based simulations, they generically predict the wrong number and type of satellite galaxies (related study here) producing a 2.4 sigma tension:

The kinematic approach yields a larger diversity in central dark matter densities than expected from the CDM population, as inferred from the stellar-to-halo mass relation, with compact ultra-faints appearing overdense and larger systems appearing underdense. For the ultra-faint dwarfs with at least 10 stars with spectroscopic measurements, this discrepancy persists at the ~2.4σ level across all considered systematic variations on the semi-analytic modeling.

The Hubble tension remains unresolved, which implies that the cosmological constant, Lamba, of the LambdaCDM model, isn't actually constant. And at galaxy scales, CDM has lots of problems:

Small-scale cosmic structure provides a powerful test of the fundamental nature of dark matter (DM). A wide range of DM models impact matter clustering on small scales, including warm, fuzzy, and (self-)interacting DM. In these scenarios, DM physics such as free-streaming, wave interference, and self/Standard Model interactions alter the abundance and internal structure of DM halos. Cosmological and astrophysical probes of nonlinear structure---including dwarf galaxies, strong lensing, the Lyman-α forest, stellar streams, and high-redshift galaxies---are therefore sensitive to these effects. 

Here, we review DM constraints provided by small-scale structure, focusing on observables that probe scales smaller than ∼1 Mpc, which define the frontier of current measurements. We summarize how these constraints have been translated to limits on microphysical DM models, and we discuss key modeling uncertainties and observational systematics. Finally, we highlight the growing importance of probe combination and simulation-based inference for this field, and we overview upcoming observational facilities that will sharpen small-scale structure tests of DM physics.

Ethan O. Nadler, Keir K. Rogers, Alex Drlica-Wagner, "Dark Matter Constraints from Small-Scale Cosmic Structure" arXiv:2607.28564 (July 30, 2026) (73 pages, submitted to Reviews of Modern Physics). The conclusion of this article states:

Over the past two decades, measurements of small scale structure have evolved from potential challenges to the CDM paradigm into a powerful probe of the fundamental nature of DM. For example, the combination of increasingly complete observations of faint galaxies and stellar streams, advances in strong lensing, and the development of flexible, empirically-grounded modeling frameworks has enabled robust inference that connects DM microphysics to data at the small-scale frontier. As a result, these probes now provide among the most stringent constraints on many DM properties, complementing LSS analyses and terrestrial experiments. At the same time, our understanding of small-scale cosmology remains incomplete, and new tensions have emerged on highly nonlinear scales, many of which are related to the inner densities of low-mass subhalos. 

Small-scale structure will likely play a central role in an eventual DM discovery. In the presence of a terrestrial detection, cosmological confirmation will be essential to show that newly-detected particles are the cosmological DM, and small-scale structure provides a uniquely sensitive avenue to achieve this goal. Conversely, evidence for departures from collisionless CDM inferred from nonlinear structure would offer critical guidance for direct detection and collider experiments by narrowing the viable particle DM parameter space. Thus, small-scale structure acts as a bridge between astrophysics and particle physics, creating interdisciplinary opportunities at the interface of astrophysical data and particle theory. 

A key milestone in the coming years will be the detection (or robust exclusion) of DM halos with masses below the galaxy formation threshold. Establishing the existence of completely dark halos would open a new observational window into structure formation and enable the most incisive small-scale structure tests of DM physics to date. On the other hand, an absence of such systems would constitute strong evidence against CDM and for DM physics beyond gravity. Either outcome will mark an important transition in our understanding of DM. 

Realizing the potential of upcoming small-scale structure data will require both observational and theoretical advances. On the observational side, next-generation facilities will dramatically increase the statistical power of current probes while enabling the first DM constraints from new data. On the theoretical side, progress will depend on accurately modeling nonlinear structure across DM scenarios, robustly marginalizing over the impact of baryonic physics on small-scale structure, and combining data from multiple probes in a unified framework. Together, these developments point toward a future in which small-scale structure enables precision tests—and perhaps discovery—of fundamental DM physics.

This article, however, is far too tentative and unwilling to drawn any conclusions from an already abundant supply of observations in its exceptionally long review of the literature and prospects for future study.

While the Hubble tension has received more widespread mainstream attention, the galaxy and galaxy cluster scale issues with cold dark matter particles is, IMHO, the far greater challenge to the LambdaCDM model. In measure after measure, it fails irremediably. 

The Linguistic Golden Age

The most notable findings of the study are that the number of languages in the world was already starting to decline five hundred years before the Columbian exchange and the Renaissance, and that small pre-agricultural populations placed an effective limit on the number of languages spoken in the pre-Holocene era. The peak number of languages was on the order of 10,000 to 35,000 according to the study under various model assumptions.

A linguistic “golden age” flourished between 1,000 to 3,000 years ago when tens of thousands of languages were spoken throughout the world, according to a new study coauthored by Yale linguist Claire Bowern that traces trajectories in global language diversity over the past 12,000 years.

The golden age was followed by a period of rapid decline in linguistic diversity that coincided with the rise of large states and multinational empires, such as the Roman Empire, the researchers found. The finding challenges a commonly held view that widespread language extinction began later, about 500 years ago, with the onset of European colonial expansion.

The languages of expanding states and empires were disproportionately likely to survive while those of absorbed, displaced, or declining populations disappeared, the researchers concluded. This means that the roughly 7,600 languages spoken or signed today represent a small and historically biased sample of the languages that once existed, which has important implications for the study of global patterns in language and culture, they said. . . .

The study, which was published July 23 in the journal Science, is the result of a long international collaboration between experts in language, demography, and evolutionary biology. . . .

Direct evidence of languages doesn’t exist before the appearance of writing about 6,000 years ago. So for the study, the researchers combined ethnographic information, estimates of prehistoric population size, and statistical and social-computational modelling to estimate linguistic diversity over the course of the Holocene — the current geological epoch that began about 12,000 years ago.

To gauge the likely distribution and sizes of populations before the advent of agriculture, the researchers used ethnographic data from 171 hunter-gatherer and fisher societies whose traditional subsistence and mobility had not been profoundly transformed by contact with food-producing populations. They combined these estimates with independent analyses suggesting that the global human population 12,000 years ago was between approximately 4.4 and 7 million. Assuming that the number of languages in the early Holocene corresponded with the number of distinct groups that the total human population could accommodate at the time, between 4,500 and 6,200 languages were spoken 12,000 years ago, the study’s models estimated.

The world immediately before agriculture was probably not exceptionally rich in languages,” said lead author Damián Blasi, an ICREA (Catalan Institution for Research and Advanced Studies) research professor based at the Center for Brain & Cognition at the Pompeu Fabra University in Barcelona, Spain. “There were most likely fewer languages than there are today. Linguistic diversity then grew alongside the human population for thousands of years.”

To capture fluctuations in linguistic diversity as populations expanded dramatically following the onset of agriculture and technological innovation and then contracted through wars, plagues, and other ecological factors, the researchers modelled thousands of possible trajectories connecting language estimates at the beginning of the Holocene with the present.

The models consistently produced patterns indicating that language diversity peaked between 1,000 and 3,000 years ago when upwards of tens of thousands of languages were being spoken worldwide, this period that the researchers call the world’s linguistic “golden age.”

That golden age ended with the rise of states and multinational empires as the dominant groups spread their languages, cultures, and pathogens to previously independent populations, the study shows. European colonialism intensified the steep decline in linguistic diversity, but did not cause it, according to the study.

The loss of so much linguistic diversity over the course of two millennia affected the development of today’s languages, the researchers said.

“The languages we see today are the survivors of a massive and highly selective historical bottleneck,” said study coauthor Russell Gray, director of the Department of Linguistic and Cultural Evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. “A linguistic feature may be common not because it is inherently efficient or better for communication, but because it happened to be carried by populations that expanded. Extinction may have shaped linguistic diversity much more profoundly than we previously appreciated.”

"Study uncovers lost ‘golden age’ of languages: A new study coauthored by Yale linguist Claire Bowern suggests that tens of thousands of languages were spoken between 1,000 and 3,000 years ago." via a Yale University press release.

Conventional linguistic reconstruction methods struggle to reconstruction linguistic pre-history much before 4,000 to 8,000 years ago.

The 7,600 languages spoken today is rapidly falling (according to Ethnologue, there are approximately 7,159 known languages spoken around the world today). A very large share of all languages spoken today have a small number of speakers or are moribund and on the brink of extinction in the next couple of generations or sooner. 

The general consensus is that between 6,000 and 7,000 languages are currently spoken. Some linguists estimate that between 50% and 90% of them will be severely endangered or dead by the year 2100. The 20 most common languages, each with more than 50 million speakers, are spoken by 50% of the world's population, but most languages are spoken by fewer than 10,000 people. . . . More than 50% of the world's endangered languages are located in just eight countries: India, Brazil, Mexico, Australia, Indonesia, Nigeria, Papua New Guinea and Cameroon.

From Wikipedia. About 107 languages are spoken by 7 million people or more and about 200 languages are spoken by a million people or more. A list of the number of languages per country can be found here. 

Roughly 40% of languages have less than 1,000 speakers (that's a total of 3,193 endangered languages) spoken collectively by much less than 3 million people out of 8.3 billion people in the world. About 10 million people speak a language that is spoken by 10,000 or fewer people. About 46 languages have only a single speaker. The Ainu language of Japan has 10 speakers. The median Australian Aboriginal language has 10 speakers. The median Native American language in the U.S. has 12 speakers. The median Brazilian indigenous language has 210 speakers. The median Papuan language has 1,315 speakers. The median Indonesian language has 3,500 speakers. The median Mexican indigenous language has 4,730 speakers. The median languages spoken in Cameroon has 10,000 speakers. The median language in Nigeria has 14,000 speakers. The median language in India has 35,000 speakers. 

Reviving an extinct or endangered or purely liturgical language is not impossible but is very difficult and there have been only about twenty moderately successful attempts to do so. The most successful effort has been the Hebrew language.

The Model Dependence Of Cosmological Neutrino Mass Estimates

Even with greatly relaxed cosmology based bounds in neutrino mass that free it from the strong model dependence it has in the deeply flawed ΛCDM model, cosmology based limits on neutrino mass have a 90% confidence level upper bound that is about five times more strict than direct measurements of neutrino mass.

The relaxed less model dependent bound on neutrino mass still limits the lightest neutrino mass to about 60 meV in an inverted hierarchy scenario, and to about 73 meV in a normal neutrino mass hierarchy. In the restrictive and model dependent ΛCDM model estimation of the neutrino masses, there is a normal neutrino mass hierarchy and the lightest neutrino mass can't be much more than 2 meV which a best fit value that is much smaller than that.

Very low neutrino masses greatly limits the role that neutrinos can play to make up the gap between modified gravity theories that account for most, but not all, dark matter phenomena, such as MOND.

Neutrino oscillations establish that neutrinos are massive, providing the only laboratory detection of physics beyond the Standard Model. Direct kinematic experiments bound the electron-neutrino mass to m(νe) < 0.45 eV (KATRIN, 90% CL), implying ∑m(ν) ≲ 1.3 eV. 

Conversely, cosmology within ΛCDM is highly constraining: Planck CMB, CMB lensing, and DESI DR2 BAO yield ∑m(ν) < 0.056 eV (95% CL), in 2-3σ tension with the inverted-ordering floor (0.10 eV). However, this bound relies on ΛCDM, while data hint at an evolving dark energy. 

To determine the model dependence of cosmic neutrino mass bounds, we deconstruct each probe's sensitivity to late-time physics and pursue two robust routes to a ∑m(ν) bound: 

(i) The existing dark-energy-marginalized route, retaining all data and marginalizing over (w(0),w(a)), is shown to also be immune to flexible binned and cubic w(a) histories, yielding ∑m(ν) < 0.152 eV, sharpening to σ(∑m(ν)) ≈ 0.043 eV with Simons Observatory lensing and Spec-S5 BAO.

(ii) A new late-Universe-free route combines primary CMB, marginalizing over acoustic-peak smoothing via Alens, with the reconstructed lensing spectrum CκκL, removing late-time expansion dependence by construction. This yields ∑m(ν) < 0.41 eV today, tightening to 0.31 eV (Simons Observatory) and 0.28 eV (cosmic-variance limit) across all tested dark-energy models. These relaxed bounds trade statistical power for model independence. Interestingly, they land in the sensitivity range targeted by next-generation laboratory experiments like Project 8 (m(νe) ∼ 0.1 eV), motivating vital synergies between future cosmological and terrestrial neutrino measurements.

Frank J. Qu, et al., "Measuring Cosmic Neutrino Masses Independently of Dark Energy" arXiv:2607.24742 (July 27, 2026).

The Pre-Greek Substrate

A nice Facebook reel discusses the pre-Greek substrate of the Indo-European Greek language for which we have about 1000 Greek words that don't appear to have Indo-European origins as evidence.

The geographic extent of the pre-Greek substrate

It notes the geographic extent of the substrate (which is similar to that of modern Greece plus the west coast of Turkey), and the subject matter of the substrate words including animals, plants, toponyms, terrain types, large sea related words, other natural phenomena, proper names, and particularly notably, most of the gods in the Greek pantheon. It also notes distinctively non-Indo-European phonemes found in many pre-Greek substrate words like "nth" and "ss" which were suffixes in the pre-Greek substrate.

My intuition is the the pre-Greek substrate had a larger than average impact on Greek compared to other Indo-European languages, but probably less than the Indo-Anatolian languages. The fact that many god names were borrowed into Greek also suggests that this may be a general feature also shared by Indo-Aryan (i.e. Sanskrit derived) and Indo-Iranian language, and perhaps by Germanic languages as well.

Some substrate source words:

Davidski At Eurogenes On The Indo-European Homeland

Davidski at Eurogenese has provided some thoughts on the Indo-European homeland in a teaser post with an updated large data set of ancient and modern DNA from Europe. He states:

(Interactive version here)

- Yamnaya is almost certainly derived from Serednii Stih (aka Sredny Stog). I've been talking about this for years and you can probably pick it up without too much trouble in the PCA above. Finally, even Iosif Lazaridis, David Reich, Nick Patterson and friends are now on board with this idea as per their latest paper on the topic (see Lazaridis et al. 2025).

- However, I'm not convinced by the Lazaridis et al. hypothesis that the Caucasus–lower Volga (CLV) cline is intimately linked to the Indo-Anatolian and proto-Anatolian expansions. That's because the CLV cline is an artifact of isolation-by-distance working for thousands of years across a vast and highly diverse landscape, and it includes a wide range of populations that usually have nothing to do with each other.

- The question of who actually spoke Indo-Anatolian first will, in all likelihood, never be solved to everyone's satisfaction. But the number of true candidate groups is actually quite small, and I reckon they're almost certainly all highlighted in my PCA above. Wink, wink, nudge, nudge.

My longstanding hypothesis is that Indo-Europeans established themselves in Anatolia close in time to the first historical attestation of their presence in the 18th century BCE, and that the Indo-Anatolian languages are more divergent than other Indo-European languages due to a stronger substrate effect from the Hattic language and related pre-Indo-European languages from Anatolia, because the substrate culture that they conquered was a vital and functioning Copper Age culture rather than the nearly collapsed Neolithic cultures that other Indo-Europeans encountered as a substrate. I believe that conventional wisdom in the field of historical linguistics attributes too much of the divergence between the Anatolian languages and other Indo-European language to the time depth from their common ancestor dialect.

New Combined Standard Model Constant Measurements

A new study tries to extract several Standard Model Constant measurements from the same data set and obtains results generally consistent with prior efforts to measure the same constants, but with greater uncertainty than the state of the art measurements of these quantities.

X17 Hypothesis Less Constrained Following Reanalysis of Data

The conclusion of a new reanalysis of X17 relevant experimental data loosens the constraints greatly. But, I remain deeply skeptical of its existence.

Also, why use units of 10^-3 GeV instead of MeV in your key chart?

[T]he revised exclusion limits no longer extend to the X17 mass of 16.88 MeV, leaving a sizeable region of parameter space for the vector-boson interpretation of the anomaly, bounded by the NA64 and Orsay constraints. Interestingly, the remaining allowed interval, 6.5 × 10^−5 ≲ εe ≲ 1.1 × 10^−4, is compatible with the recent preliminary measurement of the X17 lifetime. We further observe that, for these coupling values, the X17 decay length for a 100 GeV/c e− beam-dump experiment is of the order of few meters, resulting to an invisible signature for a missing-energy setup such as NA64-e [51]. The X17 parameters space not any longer constrained by E141 could thus be explored in the near future by NA64 through the invisible-mode dataset accumulated so far by the experiment.

Since its first observation by the ATOMKI experiment in 2018, the ∗Be anomaly has attracted considerable interest within the dark sector community as it may indicate the existence of a new fundamental particle with a mass of about 16.9 MeV, the X17. However, the minimal model describing X17 as a new vector boson is severely constrained by null results from legacy beam-dump experiments. Among these, the E141 experiment at SLAC places stringent limits on the X17 coupling to electrons εe in the 5.1 × 10^−5 ≲ εe ≲ 1.7 × 10^−4 region. 

This excludes the possibility of a long-lived X17, potentially in contrast with the preliminary estimate of the particle lifetime recently reported by the ATOMKI collaboration. The E141 limits commonly adopted in the literature rely on reinterpretations of the original analysis under solid but simplifying assumptions. While these studies provide a reliable estimate of the experiment's reach, they rely on approximations that were well justified when the boson mass was largely unconstrained. With the X17 mass now confined to a narrow region by recent experimental observations, a more refined treatment of the E141 sensitivity becomes necessary. 

In this work, we revisit the E141 exclusion limits in the X17 scenario by performing a dedicated reanalysis that incorporates a more accurate treatment of the experimental setup and signal prediction. We quantify the impact of these refinements on the excluded parameter space and discuss their implications for the compatibility between the E141 constraints and the vector boson interpretation of the ATOMKI anomalies.

A. Celentano, A. Marini, L. Marsicano, "Updated E141 constraints on a long-lived X17 vector boson" arXiv:2607.22102 (July 24, 2026).

Another recent X17 paper highlighted by @neo is as follows:

The X17 particle has been proposed to explain the invariant mass anomalies observed in electron-positron pairs during nuclear transitions at the Atomki experiment. Motivated by recent observations of 8B solar neutrinos induced coherent elastic neutrino-nucleus scattering (CEνNS), we present the first comprehensive analysis of the hypothetical boson using data from multi-ton dark matter direct detection facilities. 

We consider the new particle as a light Z′ mediator arising from a spontaneously broken U(1)′ symmetry, featuring both vector and axial-vector couplings to leptons. By evaluating the latest datasets from XENONnT, PandaX-4T, and LUX-ZEPLIN, we derive stringent limits on the effective vector coupling utilizing marginalization procedures. Our global analysis provides competitive constraints that meaningfully narrow the allowed parameter space of the model, while exhibiting a clear sensitivity to the tau-flavor coupling.

M. F. Mustamin, M. Demirci, M. Deniz, "Signatures of X17 through Coherent Elastic Solar Neutrino-Nucleus Scattering in Direct Detection Searches"arXiv:2607.12691 (July 14, 2026).

The conclusion of this article states:

Motivated by the first observation of coherent elastic neutrino-nucleus scattering induced by 8B solar neutrinos, we have derived robust constraints on the effective couplings of a light Z′ gauge boson, interpreted here as the X17 particle. Initially conjectured to explain the invariant mass anomalies observed by the Atomki experiment, this hypothetical mediator can be handled within a U(1)′ gauge symmetry framework. Crucially, we have explicitly accounted for the flavor-dependent nature of the couplings, which naturally arise from solar neutrino flavor transitions during their propagation to Earth. 

Our analysis utilized the latest datasets from direct detection searches at XENONnT, PandaX-4T, and LUX-ZEPLIN experiments. While these multi-ton direct detection facilities were fundamentally designed to search for weakly interacting massive dark matter particles, their recent milestone in detecting solar neutrino-induced nuclear recoils offers a novel and powerful avenue for probing BSM physics. We systematically evaluated the flavor-dependent effective couplings—Cνe eff, Cνµ eff, and Cντ eff—that quantify the X17 interactions with the xenon target. By rigorously marginalizing over the relevant effective neutrino couplings, we have derived comprehensive 1 dof and 2 dof limits of the effective vector couplings using each dataset released by the experiments. Our global analysis reveals that PandaX-4T and LUXZEPLIN provide relatively similar behavior, while the combined datasets effectively break individual experimental degeneracies. Most importantly, we have found that the SM hypothesis remains completely protected and consistent within the 90% CL allowed regions across all flavor combinations. Overall, our derived bounds are highly competitive with the allowed parameter spaces previously mapped by IceCube and COHERENT+reactor studies. We also highlight the sensitivity of these detectors to the tau-flavor coupling, a direct consequence of the oscillated solar neutrino flux.

A non-lepton universal coupling seems particularly dubious.

The Pipeline

I scan about 45,000 physics articles a year. I bookmark and think carefully about around 4,500 of them a year. I read the underlying article's body text for about 450 of them a year. I blog about 150 of them a year.

This is post 3,001 at this blog.

Another Gravitational Alternative To Dark Matter

Entropic gravity models, which imply that gravity is an emergent law of physics, rather than a fundamental force in its own right, are a very attractive possibility from a reductionist perspective. This paper looks at an entropic gravity theory that would eliminate the need for dark matter and suggests a way to observationally distinguish it from ΛCDM and MOND models. It doesn't work out the cosmological implications of the theory, however, although since it replicates MOND in other contexts, it can be expected to be similar to it in the area of cosmology.

While modified entropy models-such as Barrow, Tsallis, Kaniadakis, Power-law, Logarithmic, and Rényi entropies-have been widely explored in cosmological contexts, their implications on galactic scales remain largely untested. These generalizations of the Bekenstein-Hawking entropy encode quantum gravitational, nonextensive, or fractal spacetime effects and can alter the gravitational entropy-area relation. 

In this paper, we demonstrate that the entropic force framework, when applied to galactic rotation curves and the baryonic mass of galaxy clusters, uniquely selects Tsallis entropy as the specific generalized entropy formulation. We then extend this Tsallis modified gravity to globular clusters to complete the structural hierarchy from galaxies to galaxy clusters to globular clusters and to investigate its behavior as a function of system scale. 

We will show that the nonextensive parameter exhibits no correlation with any of the macroscopic quantities characterizing gravitational systems, such as mass, radius, temperature, or density. Furthermore, it has previously been shown that entropy is not well-defined within the standard thermodynamic approach to gravity. The adoption of nonextensive statistics provides a foundation for entanglement, thereby enabling a consistent definition of entanglement entropy. 

We predict the existence of galaxy clusters with δ=1 (i.e., clusters whose dynamics require no dark matter) analogous to δ=1 systems already observed at galactic and globular cluster scales. This prediction provides a unique observational test to discriminate Tsallis gravity from ΛCDM and MOND. Therefore, for the entropic gravity paradigm to be consistent with observational data across all scales-from globular clusters to galaxies to galaxy clusters-it is inevitably required to be built upon Tsallis entropy.

S. Shamari, A. Sheykhi, "Resolving Galactic and Cluster Dynamics Without Dark Matter: Tsallis Entropy as the Unique Foundation of Emergent Gravity" arXiv:2607.19435 (July 21, 2026).

The introduction to this paper in the body text provides context for the entropic gravity concept, which is follows by subsequent sections that lay out the equations implied by the theory and by its competing explanations of dark matter phenomena in detail:

The quest to understand the fundamental nature of gravity, space, and time has led to profound theoretical innovations, among which the thermodynamic-gravity conjecture stands as a pivotal insight. Originally formulated by Jacobson and later enriched by Padmanabhan’s emergence paradigm, this conjecture posits that gravitational field equations-including those of General Relativity-can be derived from thermodynamic principles applied to spacetime horizons. In this framework, the Bekenstein-Hawking entropy S = A/(4G) plays a central role, linking the geometry of horizons to the statistical mechanics of spacetime microstates. In recent years, however, various quantum-gravitational, nonextensive, and fractal-spacetime considerations have motivated generalizations of this entropy formula, giving rise to modified entropy prescriptions such as those of Barrow, Tsallis, Kaniadakis, Power-law, Logarithmic and Rényi. These extended entropies introduce new parameters that encode departures from standard thermodynamics and may reflect deep-seated quantum or geometric properties of spacetime. 

To date, research on modified entropies has been predominantly cosmology-centric. Studies have explored how such corrections alter the Friedmann equations, influence dark energy models, modify inflationary scenarios, and leave imprints on the cosmic microwave background. 

While these investigations have placed valuable constraints on entropy parameters using large-scale cosmological data, a critical and largely uncharted frontier remains: how do modified entropies manifest on galactic and sub-cosmological scales? 

Galaxies-and the dark matter halos that host them-represent gravitational systems with well-defined effective horizons and rich dynamical observables (rotation curves, velocity dispersion profiles, baryonic mass-velocity relations). Yet, the implications of horizon thermodynamics for such systems have scarcely been explored, leaving open the question of whether galactic kinematics can serve as a new, independent test bed for quantum-gravitational entropy corrections. 

Our aim here is to bridge this gap by developing and applying a framework to test modified entropies through galactic-scale observations. We posit that if horizon thermodynamics underpins gravitational dynamics, then the entropy associated with the boundary of a galaxy or a dark matter halo-be it the Hubble radius of a galaxy group or the radius enclosing a fixed density contrast should govern its equilibrium properties. Using the entropic force scenario proposed by Verlinde [1] we derive modified force laws and mass-velocity relations that depend explicitly on the chosen entropy form. These relations can then be confronted with high-precision galactic data from surveys such as SPARC (for rotation curves), MaNGA (for stellar kinematics), and other spatially resolved kinematic datasets. 

Although the origins of the dark matter problem trace back to the early 1930s with the work of Zwicky and Oort, it only became a hot research topic when Vera Rubin published her observations of galactic rotation curves. Today, after nearly a century of diverse astrophysical observations from the dynamics of galaxy clusters to gravitational lensing studies and baryon acoustic oscillations a consistent picture emerges: approximately 85% of the matter in the universe is non-baryonic. Despite extensive searches, direct detection of dark matter particles remains elusive, motivating serious consideration of alternative ideas [2–7]. 

Many different theories have been proposed to explain this puzzle without non-baryonic dark matter such as Modified Gravity (MOG), Modified Newtonian Dynamics (MOND), Carmelian theory, Cooperstock model, etc [8–12]. 

Deur does not get a mention, although his approach deserves it. References [8-12] are:

[8] J. W. Moffat, Scalar-Tensor-Vector Gravity Theory, J. Cosmol. Astropart. Phys. 2006, 004 (2006). 

[9] M. Milgrom, A Modification of the Newtonian Dynamics as a Possible Alternative to the Hidden Mass Hypothesis, Astrophys. J. 270, 365 (1983). 

[10] F. I. Cooperstock and S. Tieu, Galactic dynamics via general relativity: A compilation and new developments, Int. J. Mod. Phys. A 22, 2293 (2007). 

[11] M. Carmeli, Is Galaxy Dark Matter a Property of Spacetime?, Int. J. Theor. Phys. 37, 2621 (1998). 

[12] S. Behar and M. Carmeli, Derivation of the Tully-Fisher Law from General Relativity Theory: Doubts about the Existence of Halo Dark Matter, Int. J. Theor. Phys. 39, 1397 (2000). 

A parallel line of inquiry emerged from black hole thermodynamics, following the discovery that black holes possess entropy proportional to their horizon area and temperature. Jacobson demonstrated that the Einstein field equations are nothing but an equation of state for spacetime. Verlinde’s entropic gravity framework realizes the idea that gravity itself may be an emergent phenomenon, with spacetime possessing intrinsic thermodynamic properties. In this thermodynamic paradigm, the choice of entropy functional becomes crucial. While Bekenstein-Hawking entropy leads to standard general relativity, any alternative entropy yields modified gravitational dynamics [13–16]. 

In this work, we classify all possible entropy modifications into two types of generalized entropies. We first examine their performance in reproducing galactic rotation curves; in this assessment, only Tsallis entropy succeeds. Next, we investigate their performance in galaxy clusters. We reconstruct a well-known model and again evaluate each modified entropy. Once more, Tsallis entropy emerges successful. We then extend this Tsallis modified gravity to globular clusters to complete the structural hierarchy. After analyzing and plotting the corresponding figures, we turn to the origin of Tsallis entropy and its theoretical implications. 

This paper is structured as follows. Section II critically examines type-II entropies, demonstrating their failure at galactic and cluster scales. In Section III, we derive the Tsallis-modified force law and apply it to galaxy clusters, presenting our observational analysis of 40 clusters. We then extend this framework to globular clusters, analyzing the velocity dispersion profiles of 33 such systems. In Section IV, we discuss the theoretical foundations of nonextensive statistics in gravitational systems, drawing on the work of Chavanis and others, and interpret the physical meaning of the Tsallis parameter δ in terms of dynamical relaxation and hidden constraints. Section V presents our central prediction: the existence of dynamically relaxed galaxy clusters that are observationally dark matter-free, offering a decisive test to distinguish Tsallis gravity from ΛCDM and MOND. Finally, Section VI is devoted to closing remarks. Throughout this paper we set ℏ = c =kB =1.

Another notable new paper on galactic dynamics, which has phenomenological merit, but is probably flaws in its mechanism is:

We investigate whether the observed fine structure and asymmetry of non-averaged galactic rotation curves can be reconstructed directly from the observed HI distribution within the framework of a kinetic gas transport description. Using the observed HI density profiles separately for the approaching (north-eastern) side and the receding (south-western) side of the galaxy NGC~3198, we reconstruct the corresponding rotation curves based on the equation previously derived in Lipovka 2022. It is shown that the reconstructed curves reproduce not only the approximately flat large-scale behaviour of the observed rotation curves, but also their detailed local morphology and asymmetry separately for the north-eastern and south-western sides of the galactic disk. The obtained results indicate that the local structure of galactic rotation curves is closely connected with the local HI distribution and arises naturally as a consequence of kinetic gas transport processes in galactic disks.

Anton A. Lipovka, Anna A. Lipovka "Local morphology and asymmetry of galactic rotation curves in a kinetic gas transport framework: NGC 3198" arXiv:2607.19505 (July 21, 2026).

The abstract of Lipovka 2022 is as follows:

In this paper, I show that generally accepted methods of classical mechanics are not applicable for calculating the outer parts of the rotation curves of galaxies, where an influence of collisions on gas dynamics becomes dominant. In addition, the hydrodynamic approach cannot be used for this purpose due to an extreme rarefaction of the gas. I develop a new approach to describing the gas dynamics in outer regions of galactic disks, where the gas dynamics is determined mainly by collisions. 

Equations (free from restrictions imposed on hydrodynamics) are obtained that describe the dynamics of rarefied gas. The resulting equations relate two quantities: the tangential velocity of the gas as a function of the distance from the center of a galaxy (rotation curve) and the radial distribution of the gas density. It is shown that if the physical properties of the rarefied gas are properly taken into account, then dark matter is not required, and the "nonphysical" (non-Keplerian) rotation curves of the outer parts of the galactic disks are tailwinds that can be described within the framework of conventional gas kinetics. 

To illustrate the correctness of the obtained model, two galaxies with flat rotation curves (NGC7331 and NGC3198) are considered. From the observed rotation curves, using Eq. (14), the radial densities of the gas are calculated. An excellent agreement was obtained between the calculated gas densities and their observed values, which is a serious argument in favor of the developed model. Thus, the non-physical rotation curves of spiral galaxies represent the tailwinds of gas, the dynamics of which is naturally described by the kinetic equation without involving the concept of dark matter. The total masses of two galaxies NGC7331 and NGC3198 have been calculated. The implications for cosmology are discussed.

This theory purports to explain MOND dynamics without either particle dark matter or modified gravity, using interstellar, apparently basically baryonic, gas dynamics. Any theory that works without significant new physics deserves serious attention, but I'm skeptical that it really describes the mechanism of dark matter phenomena.