Indo-Aryan v. Indo-Iranian Religion (Speculative)

The Vedic religion of South Asia, which ultimately gave rise to modern Hinduism, can be understood as a mash-up of the proto-Indo-European pantheon, which also influenced Nordic/Germanic and Greco-Roman polytheism, with an indigenous Harappan religious substrate that had a somewhat more animistic and a somewhat less anthropomorphic character. It is a process not unlike the process seen in Europe.

In contrast, the Indo-Iranian religion of present day Iran, which appears to have emerged contemporaneously with the Vedic religion from Indo-European contributors very similar to their Indo-European counterparts, was the progenitor of Zoroastrianism, which marks a dramatic departure from proto-Indo-European polytheism, replacing it with what is typically simplified to being described as dualism rather than a polytheistic pantheon.

The open question is, what made Indo-Iranian religion depart so markedly from other Indo-European religious landscapes.

We have a fairly rich trove of written sources, both Jewish and non-Jewish, that sheds light on how Jewish monotheism emerged from Eastern Mediterranean Semitic polytheism to henotheism (in which there are multiple gods but one is pre-eminent and the center of worship) to true monotheism, with some influence from a brief and failed flirtation in Egypt with a monotheistic or henotheistic religion that was heralded by a pharaoh, then abandoned not longer after that by another one.

But in West Asia, we have pretty much only the Avesta, the core and original Zoroastrian scripture, itself to guide us.

One possibility is that the Indo-Iranians had Zoroaster who just happened to be a truly remarkable individual that no other contemporaneous culture had, to make the leap in a way that secured large numbers of followers somehow. Maybe Zoroaster charmed and won over the most powerful kings and princes of West Asia who imposed his religion upon their people. Maybe Zoroastrianism secured a mass grass roots following somehow and was co-opted by West Asia's leaders.

Alternatively, perhaps Zoroastrianism is the legacy of a pre-existing religious tradition and worldview of West Asia that had a powerful influence on the conquering Indo-Iranians, which would certainly not be unprecedented. The Hittites, for example, heavily borrowed from and adopted the Hattic religion of their predecessors, keeping the Hattic language alive as a liturgical language long after it had ceased to be a living liturgical language. The linguistically Semitic Akkadians did something similar with the Sumerian religion. The fact that the language of the Avesta is written in an Indo-Iranian dialect that is a close sister to Sanskrit, somewhat disfavors this hypothesis, but it could be that the fact that Sumerian and Hattic were written languages, while the pre-Indo-European languages of South Asia and West Asia were not, could also explain this fact.

In any of these scenarios, however, there is another point. What about West Asia in the Bronze Age caused Zoroastrianism to fill a spiritual need better filled by dualism than polytheism, that was absent from contemporaneous polytheistic cultures which came under Indo-European rule?

Religions tend to imagine the world of the divine that is parallel to the leadership structure of their own societies in their formative eras. 

Animistic religions are associated with hunter-gather societies with weak political structures of fragmentary local bands. Polytheistic religions tended to emerge in chiefdomships where a chief ruled in concern with subordinate but independently powerful other leaders in a sort of council. Egypt's flirtation with monotheism and Jewish monotheism emerged in solitary monarchies with a single clear king or queen. Chinese conceptions of the spiritual world mirrored the vast bureaucracies of its own quick emerging empire.

Was the political situation in West Asia such that the dualism of Zoroastrianism better mirrored its political reality than the chiefdom style of rule of other polytheistic early Bronze Age societies?

Perhaps, for example, the Eastern Iranian region to which the Avesta refers was ruled by a strong unified monarchy, rather than a mere chiefdomship, of the conquering Indo-Iranians, but faced a strong insurgency, perhaps from the pre-Indo-Iranian king who was deposed (perhaps associated with the Jiroft culture) or from an arguably more legitimate heir to the throne who was passed over and was seeking to regain the rule of his dynasty, at the time that Zoroaster formulates Zoroastrianism.

The fact that West Asia was an early place of metallurgy mastery and the Copper Age first and then the Bronze Age is suggestive of the possibility that its political culture may indeed have in some way differed materially from that of its Bronze Age peers, so this isn't an implausible hypothesis.

More Thoughts On Red River

The first twelve episode cours of the anime Red River a.k.a. Anatolia story, based upon the long hit manga series of the same name finished yesterday, and has prompted me to research the actual history of the period depicted in this historical fiction piece (another twelve episodes are contracted for the fourth quarter of this year).

One of the points highlighted by the series that often gets overlooked in academic research is that: (1) the Hittites, the Mittani kingdom, a Mesopotamian regime, and the Egyptian 18th dynasty, were all contemporaneous, and (2) that these kingdoms meaningfully interacted with each other, exchanging correspondence, diplomats, and brides with each other, and engaging in military conflicts with the intermediate Hittite empire.

At least two royal Egyptian brides were from the Mittani Kingdom in roughly the 14th century BCE when Red River is set.

This is especially notable because, while the everyday commoners in the Mittani Kingdom were Hurrian language speakers (a language associated with the highlands of the Zargos Mountains and to a lesser extent the eastern Anatolian highlands where the possibly related Hattic language was spoken), the Mittani elites in the 1300s BCE spoke a Sanskrit derived Indo-Aryan language (that gave rise, most famously, to the Hindi language of northern India) and worshiped Indo-Aryan gods in their pantheon that became part of the Hindu religion rather than the Avestan language and religion that was starting to emerge in what is now Iran at around this time. (A cultural affiliation that neither the anime or the manga make much of.)

The Indo-Aryan linguistic and religious link to western Iran and connection the Anatolia and Egypt, disappears, however, when the Mittani kingdom falls, for historical reasons that like its brief appearance in the Mittani kingdom have since been lost and are currently unknown.

The Mittani kingdom featured in Red River as a major military adversary of the Hitties, therefore, provides a concrete human, person to person bridge between the culture of South Asian Indo-Europeans and late Bronze Age ancient Egypt: two cultural worlds usually thought of as unrelated and independent of each other despite being contemporaneous.

Actual history is unclear over whether the famous ancient Egyptian Queen Nefertiti was one of those Mittani brides or not, as the manga and anime assert, because it is a legitimate historical possibility and makes for a good story. But the historicity of the Mittani kingdom providing two royal brides to Egypt in the historical era in which Red River is set is not seriously questioned, nor is the Red River story point that at least one of those marriages was driven to a significant extent by a Mittani expectation of receiving large amounts of gold from Egypt in exchange (although, historically, the Egypt failed to deliver the gold).

A Single Possible Direct Dark Matter Detection

The Lux-Zepplin direct dark matter experiment has detected a single event that could be a dark matter particle (see also here). But given the immense amount of searching which drives up look elsewhere effects and the myriad other possible explanations for a single outlier data point, it is not a definitive dark matter detection yet.

From my posts on this at the link:

With this detector does that mean that the dark matter candidate would interact with the weak nuclear force?

Or some novel fifth force that has a cross-section of interaction much weaker (by factors of millions or billions or so) than the SM weak force.

The DM cross-section of interaction of atomic nuclei (and hence the weak force charge of DM particles) would have to be profoundly weaker than that of neutrinos if it is a weak force interaction, which would be surprising since every SM particle with weak force interactions has the same weak force charge.

What would even be a standard for credible detection here? 3 events? 10? When would they start calling Stockholm?

Not sure, does the paper say what statistical significance this event has?

The paper estimates the global statistical significance at 2.6 sigma, with a local statistical significance of up to 3.4 sigma. But the number of events probably isn't sufficient to determine the significance. It also depends, in part, about the details of each event and how far those details are from the expected background events on the chart in the OP. 

But given the amount of searching that has been done with multiple direct dark matter detection experiments that are all roughly similar to each other, the significance after the look elsewhere effect should be much lower than the local statistical significance.

You'd probably need a local significance of something like 10 sigma to get a global significance that meets the 5 sigma discovery threshold. Also, it isn't just 5 sigma, you also need a theoretical framework to attach the result to and replication, to be a true discovery.

So, you'd need (1) to do a lot of analysis with outside peer reviewers to rule out extremely faint backgrounds that weren't considered in the original analysis or other possible non-DM sources of this outlier data point, and (2) you'd need another experiment in addition to LZ to see it.

But, this makes funding direct dark matter detection experiments similar to LZ for the purpose of replicating this result and tuned to the parameters space where this was seen a no brainer.

Another issue is that even if the event is some non-SM particle, it doesn't necessarily follow that it is a significant component of DM.

Direct DM experiments are based upon the assumptions that the total DM mass flux and DM particle momentum can be pretty well determined from Milky Way dynamics, so you are looking at a parameter space in which DM particle mass and DM particle cross-section of interaction with nucleons trade off against each other for any given result.

This outlier data point, if it is real, points to a fairly high DM particle mass (some arXiv phenomenology papers are speculating in the 1 TeV order of magnitude). But anything much above 10 keV of mass presents real problems as a major component of DM since inferred DM distributions which are "cored" rather than "cuspy" suggest that you need much smaller DM masses to reduce the core-cusp problem, and plausible self-interaction strengths of heavy DM particles still don't solve that problem in simulations.

So, even if it is DM, it might be a type of DM particle that makes up, for example, only 1% of DM, as a DM analog to something like carbon atoms in interstellar space, while the predominant component of particle DM, as a DM analog of something like hydrogen atoms, might be too light for LZ to detect significantly due to neutrino backgrounds.

Analysis of this result in other preprints include:
https://arxiv.org/abs/2609.01475
https://arxiv.org/abs/2609.01504
https://arxiv.org/abs/2609.01592
https://arxiv.org/abs/2609.02608
https://arxiv.org/abs/2609.02775
https://arxiv.org/abs/2609.02868
https://arxiv.org/abs/2609.02823
https://arxiv.org/abs/2609.02807

If there are multiple kinds of DM particles and this is only a rare and heavy member of that set, this implies that the cross-section of interaction can be much higher (and thus, much closer to the neutrino-nucleon cross section of interaction). This is because the cross-section of interaction calculations assume that there is only one kind of DM particle, so that the actual events recorded comes from interactions with 100% of the DM flux through LZ. But if this assumption is wrong and only, for example, 1% of DM particles are massive enough for LZ to detect, then the actual cross-section of interaction implied by a given number of events is 100 times greater in that example.

If DM particles of this mass are extremely rare (the DM analog to uranium or lead, perhaps, making up only one in a million or billion DM particles) within the universe of DM particles, then perhaps the cross-section of interaction could be equivalent to the strength of the weak force interaction of SM particles.

The effective lower bound of DM particle mass that LZ can detect is about 0.2-0.5 GeV, and the signal to noise ratio starts to degrade meaningfully for DM particle masses below 10 GeV. And, there are, to repeat, strong suggestions from the inferred shape of DM distributions, that the predominant share of DM particles (assuming that they exist) should be about 10 keV or less, which is about 20,000 times less massive than DM particles that can give rise to events detected by LZ which are distinguishable from background events, and about 1,000,000 times less massive than DM particles that LZ can detect with maximum efficiency.

My suspicions

I think that this result is either a fluke in the background events (which at 2.6 sigma global significance, a global significance that I suspect is actually overstated, is entirely plausible), or a methodological error.

Even if it is, however, a genuine BSM particle, the one observed seems unlikely to be a DM particle, and particularly unlikely to be a Higgsino, which is what many of the linked papers suggest. A Higgsino is fairly tightly constrained in supersymmetry theories to have properties that this particle is unlikely to have, and might even be possible to rule out with further analysis of this particular data point.

Further, supersymmetry theories are simply not credible as theoretical frameworks in the broader sense for a variety of reasons, even though a Higgsino mass of 1.1 TeV was predicted in 2012 as the mass of a Higgsino that was the sole component of dark matter according to Hall, Lawrence J.; Nomura, Yasunori (2012). "Spread Supersymmetry". Journal of High Energy Physics. 2012: 82. arXiv:1111.4519 doi:10.1007/JHEP01(2012)082

The non-detection of any hint of a Higgsino at the LHC also casts doubt on this hypothesis, although the formal exclusions from the LHC (which is always a bit dicey because it depends on the Higgsino model used and the mass splitting between it and certain other supersymmetric particles) only go up to about 1.025 TeV.

There are also lots of strong reasons from astronomy, as I just scratched the surface of above, to think that either gravity (modified, non-perturbative, otherwise) or a fifth force, rather than dark matter particles make more sense, and that heavy dark matter particles (1 TeV or more particles that are at the fringe of what LZ and other direct detection experiments can be sensitive to), at least as a primary source of dark matter, are among the least observationally favored dark matter particle hypotheses.

This doesn't inherently rule out the possibility of a new fundamental particle, and the spectrum of composite bound quark and gluon structures, except toponium (which has a very distinct signature and set of conditions in which it can be formed) pretty much top out in the low tens of GeV, far below the 1 TeV scale. Toponium is 344-347 GeV, which is still below the TeV scale. The most massive observed atom, Oganesson (element 118), specifically its isotope Oganesson-294, has a mass of only about 274 GeV, which is still well below 1 TeV. A mass of 1 TeV would require a rather large and complex molecule (not hadron molecule, but a normal molecule made up of ordinary chemical elements), so an event like this, if being properly interpreted is not a good fit for any known fundamental particle, any known or possible hadron, any known or plausible future atom or atomic element. So, if there is a real detection of a 1 TeV mass particle, it is very much beyond the Standard Model and new physics. But even if it is real, that doesn't mean that it is an important contributor to dark matter. It could be a BSM particle with nothing meaningful to do with dark matter phenomena.

Indeed, the lack of well-motivated candidates for a 1 TeV particle with a very low cross-section of interaction with nucleons (at least no larger than the weak force coupling), makes this extraordinary claim require extraordinary proof and compels a very hard look for other explanations, especially given its only modest statistical significance so far.

More Physics Quick Hits

A relationship between the Higgs boson, top quark, and Z boson masses

Maybe a coincidence, maybe meaningful. The only relation that fits, using pole masses, holds at 1.4 sigma, but tends to predict either a rather high Higgs boson mass, or a rather low top quark mass.

I have little doubt that there are deeper functional relationships between the fundamental constants of the Standard Model (or at least some of them) than are contained within the Standard Model (what I call "within the Standard Model new physics" as opposed to "beyond the Standard Model new physics"). And, even if this particular relationship is not actually true, it is close enough that it is fruitful to ask, if there is some deeper source for these experimentally measured physical constant values, what kind of relationship would produce a close coincidence like this one.

For example, I wonder if an approximation of this relationship is favored in some way by the LP & C relationship that the square of the Higgs vev is equal to the sum of the squares of the fundamental SM particle masses, or by the approximate, but not exact, equality between the sum of the squares of the fundamental fermion masses and the sum of the squares of the fundamental boson masses.

Indeed, the paper notes that: 

After the Higgs discovery the numerical observation M(H)^2 ≃ M(Z)*M(t) (1) was proposed as a possible electroweak mass coincidence involving the heaviest spin-0, spin-1/2 and spin-1 representatives of the Standard Model (SM) spectrum.

(The citation for this sentence is to a paper by the author of the current paper: E. Torrente-Lujan, "The Higgs mass coincidence problem: why is the Higgs mass M2 H = MZMt?", Eur. Phys. J. C 74 (2014) 2744, arXiv:1209.0474.)

This suggests that there might be a fuller relationship that involves addition masses on the Standard Model spectrum beyond the heaviest ones that might provide correcting terms bringing the relationship to a more exact one.

I also seem to recall that there theoretically expected mass of the W boson in the Standard Model is a function of the Z boson mass, the top quark mass, and the Higgs boson mass, based upon electroweak unification in some way, but have never seen that relationship spelled out in detail. I have only seen the abbreviated leading order relationship between the W boson mass and Z boson mass that is related to the electromagnetic force and weak force coupling constants. 

The paper doesn't evaluate the "arithmetic relation" with the theoretically predicted W boson mass of 80.357 ± 0.006 GeV, but because that value is lower than the PDG value of 80.3692 ± 0.0133 GeV, it should be a somewhat better fit with the theoretically predicted W boson mass. As it turns out, this difference doesn't matter much, and neither does the difference between the Higgs boson mass that they use of 125.2 ± 0.11 GeV and the lower value of the Higgs boson mass of 125.09 GeV that is sometimes used. Indeed, the greater precision of the theoretically estimated W boson mass may increase the statistical significance of the discrepancy somewhat.

The relation M(H)^2 ≃ M(Z)*M(t), previously proposed as a non-trivial Higgs mass coincidence, is reconsidered with present electroweak inputs and with a scheme-consistent matching analysis. With the 2025 PDG values for M(Z), M(W) and M(H), and the ATLAS-CMS direct top-mass combination, the pole-level ratio is ρ(Zt)=M(Z)*M(t)/M(H)^2 = 1.00362 ± 0.00261. Thus an exact pole-level geometric relation predicts either M(H) = 125.426 ± 0.120 GeV or M(t) = 171.898 ± 0.302 GeV, which is still a 1.4σ test rather than an exclusion. 

By contrast, the companion arithmetic relation gives ρ(Wt) = (M(W)+M(t))/(2M(H))=1.00994±0.00159 and is not a viable exact mass sum rule. 

We then evaluate the complete NNLO weak-scale MS bar matching formulae at μ=M(t). In the standard convention one obtains ρˆ(Zt(M(t)) = √(g(2)^2+g(Y)^2) * y(t)/(4√2λ) = 0.96714±0.00361. Consequently, the exact running-coupling boundary condition λ =  g(Z)y(t)/(4√2) at the top scale would predict M(H) = 123.19 ± 0.20 GeV, or equivalently M(t) = 177.81 ± 0.50GeV when M(H) is held fixed. This is incompatible with the measured point. 

A possible symmetry explanation must therefore act on pole-level threshold quantities, or provide a finite matching factor κ(th) = 1.0340 ± 0.0039 at the electroweak scale. We formulate this requirement as a target for custodial/top-Higgs or triality-like symmetry extensions.

E. Torrente-Lujan, "The Higgs-top-Z mass coincidence relation after NNLO matching" arXiv:2605.21721 (May 20, 2026) (Report number: FISPAC-TH/3145-26, UQBAR-TH/26-97234).

Another key chart from the paper is this one:

The Lambda predictions are very far from the mark, as are the "arithmetic relation" estimates. The other relationship still has some tension with the experimental results but isn't ruled out.

Bounds on new neutrino physics

The constraints on BSM physics continue to narrow. In the Standard Model, the neutrino magnetic moment is predicted to be far below the threshold of current experimental detection, and the neutrino has an exactly zero electromagnetic charge. These results are consistent with those predictions and thus constrain BSM neutrino physics to very slight deviations from the SM predictions. Non-standard interactions of neutrinos are likewise constrained materially.

CODATA 2022 gives the value:

     ${\displaystyle {\sin }^2{\theta }_{\mathsf{\text{w}}}=1-{\left(\frac{m_{\mathsf{\text{W}}}}{m_{\mathsf{\text{Z}}}}\right)}^2=0.22305(23).}$

So, the Weinberg angle measurement from the CONUS collaboration, while consistent with the world average measurement at the two sigma level, is too imprecise by two orders of magnitude to add meaningfully to our knowledge of that physical constant compared to the value obtained from simply plugging in the world average measured values of the W boson mass and the Z boson mass (or from calculating it in electroweak unification theory from the electromagnetic coupling constant and the weak force coupling constant so e^2/g^2 = sin^2 theta(W).

Its detections with pion-decay-at-rest, solar and recently with reactor antineutrinos by the CONUS collaboration render coherent elastic neutrino-nucleus scattering (CEνNS) an established tool for investigations within and beyond the Standard Model (SM). The CONUS experiment located at the nuclear power plants in Brokdorf (Germany) and Leibstadt (Switzerland) operates Germanium semiconductor detectors in a compact shield at close distance to the reactor core. An observation with 3.7σ significance is reported at the Leibstadt site, showing good agreement with its SM prediction.

Physics investigations performed with the last datasets collected at the Brokdorf reactor and with the first data obtained at the Leibstadt site are summarized. By using the experimental analysis framework, the presented results contain the full systematics that underlie the experiment. 

Previously determined limits with neutrino-electron scattering on the neutrino magnetic moment and a neutrino millicharge are improved to μ(ν) < 5.18⋅10^−11μB and q(ν) < 1.76⋅10^−12e0 (90% C.L). Further, the scale of new physics related to NSIs is improved to ΛNSI = 145 GeV and limits on the coupling of light new mediators are lowered down to 4⋅10−7 (90% C.L.) with the new data. Finally, the determination of the Weinberg angle with CEνNS and reactor antineutrinos yields sin(θ(W))^2  = 0.28 +0.03 −0.04 at a momentum transfer of ∼10 MeV.

N. Ackermann, et al., "New constraints on physics within and beyond the standard model from the latest CONUS datasets" arXiv:2605.22815 (May 21m 2026).

The abstract is unclear about what there is 3.7 sigma evidence of, but the body text clarifies that: "With data collected there since 2023, a successful CEνNS detection was reported with 3.7σ significance."

The body text explains some of the theoretical motivation for the paper:

On theory side CEνNS has become an interesting tool for investigations within and beyond the standard model (BSM) because of its flavor-blind and, in principle, threshold-free properties [21–27]. Within the SM it enables measurements of the Weinberg angle sin^2 θ(W) at the MeV scale with neutrinos and probe modifications of the involved couplings, i.e. via radiative correction [28–31] or investigation of the nuclear form factor when deviating from full coherence, i.e. with higher neutrino energies from πDAR sources [32–36]. BSM searches can be performed by testing for new neutrino interactions, for example in the context of heavy new physics via non-standard neutrino interactions (NSIs)[37–43] or new light mediators [44–53]. Neutrino (electromagnetic) properties [26, 27, 54–56] or emerging new particles may be probed as well [57–59]. Furthermore, future applications in the context of multi-messenger astronomy [60–62] or nuclear safeguarding seem promising [63, 64]. Experimental upscaling in the near future will allow such investigations via precision CEνNS measurements.

Ancient Tooth Proteins Tell Tales

An analysis of six ancient Homo erectus tooth proteins from three locations in China, a Denisovan tooth protein, and some modern human and animal tooth proteins reveal some notable insights. Bernard's Blog has the story. Proteins in teeth are easier to recover than ancient DNA and can serve as a proxy for it in cases like these.

Interestingly, it implies that a tooth enamel protein found in 1% of humans in or near the former Denisovan range, and Denisovans have a tooth enamel protein also found in Chinese Homo erectus, probably due to introgression from Homo erectus to Denisovans and then from Denisovans to modern humans, in the view of the researchers.

John Hawk has a discussion of the paper, however, that interprets the data differently:

All six teeth share two derived amino acid changes, both in the sequence of an enamel matrix protein known as ameloblastin, or AMBN. One of these hasn’t before been seen in hominins: a change from alanine to glycine at position 253 of the sequence, or A253G. The other is 20 positions downstream, swapping in valine for the ancestral methionine, M273V. The DNA mutation encoding this change is shared by both the Denisova 3 and Denisova 25 genomes. The M273V amino acid change itself is in the Harbin and Penghu 1 dental proteomes—part of why they align with Denisovans. A number of genomes from modern people also share this change, possibly from Denisovan ancestors.

The hypothesis presented by Fu and coworkers is that Homo erectus was the source of M273V, and its presence in Denisovans is a result of introgression. In support of this idea of introgression, they note earlier research on the Denisova 3 and Denisova 25 genomes that suggests a contribution from a “superarchaic” source population. Many—including me—have speculated that this superarchaic ancestry came from H. erectus. Fu’s team may have just proved it.

But I don’t think these teeth are Homo erectus.

Their estimated ages, all around 400,000 years ago, are prime Denisovan time. Fu and coworkers find that all the teeth share a derived link with later Denisovan genomes. For me, the most likely hypothesis is that these teeth come from a population within the Denisovan branch of humanity.

This situation is basically the same as the Sima de los Huesos fossils. Those remains are around 430,000 years old. Those fossils look like Neanderthals in some subtle ways, but until DNA was recovered from them, many researchers considered them to be part of a different group, often called Homo heidelbergensis. DNA revised both the timeline and their identification.

It may seem heretical, but I think protein data may be about to do the same for fossils from East Asia.

Physics Quick Hits

Lots of interesting papers today. Little time to write, so only minimal commentary for now.

The reactor antineutrino anomaly still isn't real.

The Reactor Antineutrino Anomaly refers to the deficit observed between the average event rate measured in reactor antineutrino experiments with respect to the theoretical prediction. This anomaly was first identified in 2011 (2.5σ) as a consequence of the Huber-Muller reactor antineutrino flux calculation. It was thought to be resolved in 2021 as a result of new reactor antineutrino flux calculations, with a reduction to about 1σ. In this work, we examine the latest reactor antineutrino flux calculation published in 2023 by a French research group. This work represents the first summation model to include a comprehensive uncertainty budget. The result indicates a revival of the Reactor Antineutrino Anomaly at the level of 2.2σ. We also consider the usual simplest explanation of the Reactor Antineutrino Anomaly by active-sterile neutrino oscillations. We present the constraints on the oscillation parameters and we derive a tension of 3.8σ with the results of gallium source experiments (Gallium Anomaly) taking into account also the solar neutrino and KATRIN bounds, that of the combined short-baseline reactor spectral ratio measurements, and that of the Daya Bay search for a sub-eV sterile neutrino. Since the tension may be due to underestimated systematic uncertainties and the main tension is between the gallium data and the other data, we finally present the results of a global analysis with enlarged gallium uncertainties, which reduce the global tension to 1.3σ.

C. Giunti, Y.F. Li, R.P. Zhang, "Revival of the Reactor Antineutrino Anomaly" arXiv:2605.10353 (May 11, 2026).

Intriguing.

The charged-lepton Koide relation remains a striking empirical regularity in Standard-Model flavor data. We prove that for any positive mass set with Koide ratio Q0, the one-particle extension Q(m1,…,mN,x) has a unique global minimum Qmin=Q0/(1+Q0) at m∗=[(∑imi)/(∑imi‾‾‾√)]2. This exact kinematic result defines a unique extension benchmark. For the measured charged leptons it gives mℓ∗=1.25534(16)GeV and Qexp4,min=0.3999978(43); in the ideal Koide limit QKℓ=2/3, the corresponding minimum is exactly 2/5. In the effective-participant language Neff≡1/Q, the optimal one-particle extension increases Neff by one, while the equal-k multiplet extension increases it by k. The one-particle Neff profile is exactly Lorentzian in a dimensionless share-mismatch coordinate u, which we interpret kinematically rather than dynamically. Using charged-lepton pole masses with the PDG~2024 own-scale MS⎯⎯⎯⎯⎯⎯⎯⎯⎯ charm mass gives Q(e,μ,τ,c)=0.4000025(64), i.e. 11.7ppm above the measured-input benchmark and 6.2ppm above 2/5. This intentionally mixed-definition comparison is treated only as a phenomenological coincidence. To calibrate it within a stated benchmark class, we perform an exhaustive common-scale scan over non-neutrino Standard Model 2-body and 3-body seeds with one added mass. The charged-lepton-plus-charm continuation ranks 33/12,720 in the raw trial set, 24/2,640 after collapsing repeated scale realizations, and 6/756 within the fermion-only collapsed subset. We present the charm case as an empirically calibrated example of the theorem, not as a dynamical flavor model.

K. Hübner, "A minimization theorem for the Koide ratio and its Standard Model calibration" arXiv:2605.09651 (May 10, 2026).

So what?

Koide's charged-lepton relation suggests that (me‾‾‾√,mμ‾‾‾√,mτ‾‾‾√) is the natural family vector. We construct an effective compact-cycle model in which this vector is sampled from one real amplitude Z(ϕ) on an internal circle, while the masses are quadratic overlaps, ma∝|Z(2πa/3)|2. The amplitude is built from the two lowest antiperiodic modes on the circle; their symmetric square is periodic and gives the minimal three-harmonic family space e^iϕ,1,e^−iϕ. A reality condition together with the requirement that the amplitude comes from the square of one two-component spinor fixes the relative weights required by Koide's 45º geometry. The remaining orientation angle is fixed by matching one C3 family shift to transport on the full circle: integrating out the higher Fourier harmonics gives the Berry dressing that enters the determinant term and selects θℓ=−2/9. Using me and mμ as inputs, the model predicts mτ=1776.97MeV.

Kirill Shulga, "Charged-Lepton Koide Geometry from a Green-Dressed Compact Family Cycle" arXiv:2605.10245 (May 11, 2026).

Similar to another recent paper.

We show how, by exploiting the process of Coherent Elastic neutrino (v) Nucleus Scattering (CEvNS), neutrinos produced by nuclear reactor experiments appear to corroborate the evidence of the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly. We base our analysis primarily on CONUS+ and Dresden-II data, which, when combined with CEvNS data from COHERENT and neutrino oscillation data from IceCube, single out a unique region of couplings to neutrinos and nuclei.

Johan Rathsman, Joakim Cederkäll, Yasar Hicyilmaz, Else Lytken, Stefano Moretti, "The X17 Existence Hinted at by Nuclear Reactor Neutrinos" arXiv:2605.10689 (May 11, 2026) (Short version of 2603.15246 using a different model for the X17).

Neutrinos do not have negative mass, so something isn't quite right in the model to estimate its masses from cosmology.

Recent baryon acoustic oscillation (BAO) distance measurements, when combined with Cosmic Microwave Background (CMB) observations in the ΛCDM framework, lead to a preference for negative neutrino masses. We investigate whether this neutrino mass anomaly can be alleviated by a class of astrophysically motivated reionization histories. Using a frequentist analysis, we find that some reionization histories can move the best-fit value of ∑mν to a positive value and bring ∑mν ≃ 0.06 eV into the 95% confidence interval. To separate the effect of the total optical depth from that of the details of the reionization history, we compare a high-τ history with a two-step tanh-like reionization history of the same τ. The resulting Δχ2(∑mν) profiles are nearly identical. This indicates that the effect is mainly driven by the total optical depth, while the details of the reionization history play only a minor role.

Yi Cheng Dai, Wei Liao, "Reionization History and Neutrino Mass" arXiv:2605.10116 (May 11, 2026).

As expected.

Modified Newtonian Dynamics (MOND) is a paradigm that can do away with dark matter at galaxy scales, but displays a residual missing mass discrepancy in galaxy clusters. Prompted by the updated JWST-based gravitational lens model of the Bullet Cluster, I confirm here that this cluster exhibits the same residual missing mass discrepancy as other clusters of similar mass in the MOND context. Moreover, this missing mass should be mostly collisionless, since it is centred on the galaxies of the Bullet Cluster.

Benoit Famaey, "On the residual missing mass of the Bullet Cluster" arXiv:2605.10022 (May 11, 2026).

Color me skeptical. It will take a closer look to poke holes in it, however. I suspect that while it may point out problems in toy-model MOND and some other models, this data could actually point the way towards a better modified gravity theory rather than towards dark matter particles which have myriad problems of their own that are ignored in this study.

Modified gravity theories such as Modified Newtonian Dynamics (MOND) and Scalar-Tensor-Vector Gravity (STVG) have been proposed as alternatives to dark matter, but decisive tests have been hindered by degeneracies between baryonic structure and gravitational laws. Here we break this degeneracy using independent, high-precision constraints: the Milky Way radial rotation curve, vertical phase-space spirals from Gaia, and a broken-exponential stellar disk. A joint reconstruction of the radial and vertical gravitational fields reveals a structural inconsistency in modified gravity -- no model can simultaneously reproduce both observations. Our results strongly disfavor MOND at >13σ and STVG at >4σ. In contrast, dark matter halo models naturally explain the observations, providing a self-consistent test of gravity on galactic scales.

Zheng-long Wang, Yue-Lin Sming Tsai, Lan Zhang, Yin Wu, Haining Li, Xiang-Xiang Xue, Hongsheng Zhao, Yi-Zhong Fan, "Milky Way Dynamics Favor Dark Matter over Modified Gravity Models" arXiv:2605.10857 (May 11, 2026).

A Notable Coincidence Related To The Proton Mass And Charge Radius

There is a functional relationship between the mass of the proton and the charge radius of the proton that is consistent with experimental measurements of those quantities, that doesn't have an obvious cause.

The simple proton mass and charge radius relationship

From @dandb at Physics Stack Exchange on May 5, 2016 (ten years ago). This can also be stated another way:

The charge radius of the proton is almost exactly four times the reduced Compton wavelength of the proton.

The reduced Compton wavelength is a natural representation of mass on the quantum scale and is used in equations that pertain to inertial mass, such as the Klein–Gordon and Schrödinger equations.

Equations that pertain to the wavelengths of photons interacting with mass use the non-reduced Compton wavelength. A particle of mass m has a rest energy of E = mc^2. The Compton wavelength for this particle is the wavelength of a photon of the same energy.

The reduced Planck's constant, h-bar, is Planck's constant divided by 2π. So, this relationship could also be stated as r = 2h/πmc, for Planck's constant h, the proton charge radius r, and the proton mass m.

This relationship is consistent with experimental measurements made to 0.05% precision

The uncertainty in the "predicted" value of the charge radius of the proton from this relationship, which is 0.84124 to five significant digits, is negligible, because the speed of light (c) and the reduced Planck's constant (h-bar) are quantities used to define SI units of measurement which are thus known "exactly" in terms of SI units of measurement, and the mass of the proton is known to the exquisite precision of about one part per hundred billion. See the Particle Data Group table of physical constants.

The Particle Data Group world average value is currently 0.8409(4) fm, i.e. a one sigma range of 0.8405 to 0.8413 This is a relative uncertainty of 0.048% (i.e. about one part per two thousand).

The PDG value is also consistent with a February 11, 2026 measurement of the charge radius of the proton with a relative uncertainty of 0.18% published in the prestigious peer reviewed journal Nature found it to be rp = 0.8406(15) fm, i.e. a one sigma range of 0.8392 to 0.8421 fm. 

So, the conjectured relationship is consistent with the experimentally measured value of the charge radius of the proton. 

At the time that this Physics Stack Exchange post was written, there was a discrepancy between the electron measurement of the proton charge radius and the muon measurement of the proton charge radius, but that has since been resolved. The muon measurement was found to be correct, and the electron measurement was found to have been incorrect due to experimental measurement errors not fully reflected in the stated uncertainty of the measurement.

This "prediction" is also notable because it is a testable hypothesis. As measurements of the proton charge radius grow more precise, we can find out if the experimentally measured value continues to be consistent with this prediction.

For example, if this hypothesis is merely numerology with no deeper meaning, it would be highly likely that it would grow less consistent with the experimental measurement if the experimental measurement's precision were increased by a factor of ten. And, in fact, experiments to do that are on the agenda of the physics community.

Analysis

What makes this relationship surprising?

Since the charge radius of the proton and the mass of the proton are both, in principle, derived quantities in the Standard Model, that this isn't actually a "coincidence" so much as it is a simple relationship arising from Standard Model physics whose source isn't trivially obvious.

The reason that it isn't trivially obvious is that the calculation of the mass and charge radius of the proton in the Standard Model are primarily functions at leading order of (1) the QCD coupling constant (which describes the strength of the "strong force") evaluated with non-perturbative QCD, (2) the mass of the up quark, (3) the mass of the down quark, and (4) the electromagnetic coupling constant. Yet, none of these experimentally measured physical constants have a functional relationship to Planck's constant or the speed of light.

There are comparatively minor contributions to these quantities that tweak their value beyond the leading order values from the masses of the other quarks (especially the strange quark), the weak force coupling constant, the W boson mass, and the CKM matrix elements (especially the  two elements of the nine elements in the matrix involving up-down quark transitions and up-strange quark transitions).

The reason that this relationship is surprising is that there is no known functional relationship between the reduced Planck's constant or the speed of light, and the other experimentally measured determinants of the proton mass and the proton charge radius (such as the Standard Model coupling constants, the quark masses, and the CKM matrix elements).

Three possible explanations

The stack exchange thread linked above contains some speculations as to why this is true, some more credible than others, but they are only speculations. For example, Michell Porter notes that:

Via P.R. Silva (eqn 6), I have run across a heuristic model of the nucleon in which M = 4/R (in natural units). Here R is the radius of the bag in the "bag model". See Xiangdong Ji, "Mass of the hadron", slide 20. I have not found where this argument originates, but a remark in a 1994 paper by Ji (see paragraph beginning "In the chiral limit...", on the final page) hints at it.

One possibility, which is to some extent the default one, is that this numerical coincidence of these two values has no deep meaning or connection and doesn't point to anything. In other words, this relationship just happens to hold for one hadron out of hundreds, for one of a large set of possible combinations of other physical constants that have no actually physical relationship to each other.

Another reason that this could be true is that the contributions of the experimentally measured constants cancel out in the combination of the proton mass and the proton charge radius, since the same experimentally measured constants enter into both calculations.

If true, this would suggest that should be a way of calculating the proton charge radius from first principles that more transparently and obviously reveals this cancelation.

This would be very interesting, would provide us to a deeper understand of the Standard Model and hadron physics. 

It would also suggest that this relationship ought be to generalizable in some way to the relationship between hadron mass and hadron charge radius for many hadrons (hadrons are composite particles made up of quark and/or gluons bound by the strong force of the Standard Model).

A calculation in this form would also have practical use, because the first principles Standard Model calculation of the proton mass has less than one part per thousand precision (vastly less than the precision of the experimentally measured value). And, in general, this would provide a quick and easy way to calculate hadron charge radii (which are no more precise than first principles calculations of hadron masses using current methods, see also here) which could then be compared to experimental measurements of hadron charge radii.

A third possibility, which would be even more grand, is that the values of the physical constants of the Standard Model that go into calculating the mass and charge radius of the proton actually have some deep functional connection to Planck's constant and the speed of light that has not previously been recognized or hypothesized.

Theoretical X17 Considerations And Related Conjectures

Could the X17 resonance, if it is even real, be an electromagnetically bound light quark-light antiquark meson?

This explanation is much more attractive than a new fundamental particle, as it wouldn't involve beyond the Standard Model physics, and would instead involve a low energy electromagnetically bound up-antiup or down-antidown pair of quarks.

It has to be electromagnetically bound, rather than strong force bound, because a neutral light quark-antiquark pair bound by the strong force, i.e. a neutral pion, has a mass of about 135 MeV, mostly due to the binding energy of the gluons confining them in a hadron. 

This said, this theory has a big problem. 

Why aren't the light quarks confined in a QCD bound hadronic state? 

The only times quarks are not in QCD bound hadronic states that have so far been observed are shortly after top quarks form (because they almost always decay before they can hadronize, although we just learned in 2025 that in rare cases a top anti-top quark pair can form toponium in a QCD bound state the persists very briefly) and in quark-gluon plasma at temperatures corresponding to about 1-2 GeV (i.e. 11-23 trillion Kelvin).

The invariant mass spectrum of e+e− pairs produced in high-energy Pb-emulsion collisions at 160 A GeV at CERN SPS exhibits a complex structure of many resonances resting on top of a broad enhancement at invariant masses below 50 MeV, with the prominent resonance at 19 ±1 MeV providing independent support for the hypothetical X17 particle. 

We show that this complex structure may be coherently described as signatures for the neutral color-singlet qq¯ quark matter in both its deconfined and confined phases. That is, the broad enhancement may arise from thermal annihilation of QED(U(1))-deconfined quarks and antiquarks into e+e− pairs at the phase transition temperature Tc(QED), theoretically estimated to be 4.75 ± 1.2 MeV from the transitional equilibrium condition. The observed 3±1 and 7±1 MeV resonances may correspond to the QED(U(1))-deconfined dd¯ and uu¯ Coulomb bound states near their quark rest masses, respectively, whereas the observed 19 ± 1 MeV resonance may correspond to the QED(U(1))-confined isoscalar QED meson. 

The approximate agreement between the theoretical and the experimental spectrum suggests that both QED(U(1))-confined and QED(U(1))-deconfined neutral color-singlet qq¯ quark matter may have been produced in these high-energy Pb-emulsion collisions. We propose future experiments to confirm or refute these findings.

Cheuk-Yin Wong, "Possible Evidence for Neutral Color-Singlet qq¯ Quark Matter from High-Energy Pb-Emulsion Collisions" arXiv:2604.23473 (April 25, 2026) (21 pages).

Some conjectures

What would work without breaking the rules of the Standard Model, however, is if the 3 and 7 MeVs were light quark-antiquark pairs that were produced and immediately annihilated before  they could hadronize, and if the 19 MeV resonance was an electromagnetically bound positron-electron state (i.e. positronium). Positronium has a ground state mass of 1.022 MeV  (twice the 0.511 MeV mass of an electron or positron), however, with excited states varying in mass by single digit eV amounts per state, which wouldn't generate a single resonance at 17-19 MeV. 

Another possibility is that the observed 3 ± 1 MeV resonances may correspond to the QED(U(1))-deconfined uu¯ Coulomb bound state near its quark rest masses, that the 7 ± 1 MeV resonances correspond to the QED(U(1))-deconfined dd¯ Coulomb bound state and also to uu¯uu¯ Coulomb bound state near their respective quark rest masses, and that the observed 19 ± 1 MeV resonance may correspond to the QED(U(1))-deconfined dd¯dd¯ Coulomb bound state.

The light quark masses, according to the Particle Data Group (admittedly at the 1-2 GeV energy scale and not the low single digit to tens of MeVs energy scale) is as follows:

The rest mass of four d-quarks is 18.8 MeV, which is right where the resonance is observed.

In this hypothesis, these resonances fail to hadronize because the e+e− pairs that produced one or two light quark-antiquark pairs didn't have enough mass-energy to form a 135 MeV neutral pion, so they instead formed one or two deconfined quark-antiquark pairs that quickly annihilate again because the system had enough energy to create the quarks, but not enough energy to create the bound system of quarks and gluons necessary to form a pion. This has the virtue, again, of not requiring any BSM fundamental particles or new forces.

A four quark solution requires angular momentum that wouldn't normally be present in a simple e+e− pair, but if there were two e+e− pairs in close proximity, both with only modest kinetic energy, which is plausible in the context of the complex overall environment of the high-energy Pb-emulsion collisions generating the data here, or the interactions of the full fledged multi-nucleon atoms present in other contexts where there are claimed sightings of the X17 resonance, a coincidence of two low energy e+e− pairs would be expected with some calculable frequency.

This explanation would still be ground breaking, as it would represent a third circumstance, previously unknown and not predicted, where quarks are (briefly) deconfined. But it would be far less radical than most of the alternative explanations.

South American Genetic History

I remain skeptical that the Australasian ancestry is as ancient as claimed. It is much less than 2%, maybe a hundred times less, and the regional variation in its frequency is far too great for it to be ancient. I suspect an origin in Polynesian sea farers that may be obscured by natural selection against some signature Polynesian genes. 

I have not yet seen any really solid evidence that it has been present for 10,000+ years, or any explanation for the extremely varied frequency of these genes in the populations where they are found, indicating a very recent dispersal to these populations that hasn't had time for these frequencies to harmonize. 

South American ancient DNA samples are few and far between at that time depth, and this paper has some of them, but a lot of the references supporting this analysis are in supplementary materials and extended data, or references to other papers, and the nature of the ancient DNA sample is one I haven't been able to look at closely yet. As I've only had time to cut, paste, and highlight, rather than enough to do a proper critical analysis of this claim. 

I'll add more analysis in an update in this post, if time permits, which may or may not happen (I'm busy preparing for an upcoming jury trial).

[A] study published today in Nature reveals these migrations were anything but simple. Examining ancient and modern genomes collected from across South America and beyond, the team found that genetically diverse groups populated the continent in at least three separate pulses. And some people or communities carried with them possibly advantageous genes acquired from long-ago Australasian ancestors. . . .

His team published a complementary study today in Current Biology, finding evidence of unexpected genetic diversity and otherwise invisible migrations in 52 ancient genomes from Argentina and Uruguay.

In the Nature study, Tábita Hünemeier, a geneticist at the University of São Paulo and the Institute of Evolutionary Biology, collaborated with researchers and Indigenous communities across Latin America to sequence 128 whole genomes from living people from north Mexico to southern Argentina. The team then analyzed them alongside existing databases and previously published ancient genomes.

Previous work had identified the first two waves of settlement in South America, the earliest of which included people related to the Anzik child, who was buried in Montana 12,700 years ago. A second dispersal followed about 9000 years ago and ultimately contributed more to the genomes of most ancient and modern South Americas, including those Posth studied.

Hünemeier and her team found evidence of a third dispersal, whose genetic signature first appears in their data about 1300 years ago and then spreads widely across the continent and even into the Caribbean. The newcomers show hints of being related to Mesoamericans from Mexico and Central America, but so far, researchers don’t know exactly where they came from or who were their closest relatives. “Without the source population and more direct evidence [of a third pulse] from ancient DNA, it’s hard to really wrap our heads around” how and when a third migration might have happened, Posth says.

The study also digs deeper into a mystery that has bedeviled the genetic history of the Americas for over a decade: How did traces of Australasian ancestry end up in some ancient and modern South American genomes? Genetic variants from this lineage make up only about 2% of ancestry in the people who carry it, but that proportion has stayed remarkably consistent over the past 10,000 years. “This signal is found again and again and again,” Posth says. “It must mean something.”

Hünemeier suspects people carrying this ancestry were among several distinct populations that lived for thousands of years in Beringia, the now-drowned landmass that connected eastern Siberia to Alaska, and that it eventually spread southward into the Americas from there. (This Australasian ancestry, sometimes known as Population Y or the Ypykuéra signal after the Tupi word for “ancestor,” is different from the genetic sequences some Polynesian populations share with South American ones. Scientists continue to debate how that more recent gene flow happened—for example, whether Polynesian voyagers may have reached western South America about 800 years ago—but the findings from the Nature paper have no bearing on that mystery.)

From Science.

Both of these papers are open access.

The Nature article and its abstract:

Indigenous peoples of America represent the last principal expansion of humans across the globe, yet their genetic history remains one of the least explored. Although these populations have inhabited the continent for thousands of years, their evolutionary history remains largely unresolved, owing to the limited availability of genomic data. 

Here we present data on 128 high-coverage Indigenous American genomes and show they harbour extensive and previously uncharacterized genetic diversity, reflecting at least three dispersals into South America, followed by regional differentiation and long-term continuity. 

We identified widespread natural selection signals in genes associated with immunity, metabolism, reproduction and development, which were shaped by adaptation to diverse environmental conditions. 

Notably, several genomic regions exhibit a remarkable allele sharing with Australasian populations, probably originating from an ancient admixture event and partly maintained by selection for more than 10,000 years. 

We also detected distinct contributions from archaic humans with adaptive introgression affecting key biological functions. The limited overlap between the regions of Australasian affinity and archaic ancestry indicates independent evolutionary origins of these signals. These findings challenge simplified models of continental settlements and show a more dynamic and complex evolutionary history for the Indigenous peoples in America.

Castro e Silva, M.A., Nunes, K., Ribeiro, M.R. et al. :The evolutionary history and unique genetic diversity of Indigenous Americans." Nature (April 22, 2026). https://doi.org/10.1038/s41586-026-10406-w

The section on archaic and Australasian ancestry in the body text of the Nature article states (with citations omitted):

Affinity with Australasians and archaics

Some Indigenous American populations show elevated genetic affinity to present-day Australasians relative to other groups contradicting a single non-Arctic Indigenous American clade. This affinity is best explained by admixture between the ancestors of Indigenous Americans and an unsampled ancient Asian population, termed Ypykuéra (here referred to as Ypykuéra ancestry), partially related to a sister clade of present-day Australasians.

We assessed genetic affinity between ancient and modern Indigenous Americans and present-day Australasians, the closest living proxies for Ypykuéra ancestry. We applied F-statistics to modern Indigenous American pairwise comparisons and to comparisons including ancient individuals.

Several Indigenous groups, including the Awajún, Ayoreo, Guarani, Karitiana, Sirionó, Suruí and Tsimané, show significant excess genetic affinity to Australasians relative to other present-day populations (Z > 3). These groups span eastern and western South America and the Chaco, with the strongest enrichment in the southwestern Amazon, where five of these seven populations are located.

A second analysis detected at least one individual with significant affinity in all examined clusters, except Arctic and northern North American groups, which were excluded from this analysis because of partial or complete ancestry from independent Siberian dispersals. The earliest signal occurs in the 10,400-year-old Sumidouro individual. Signals persist from the Early Holocene to the present, increasing in frequency during the Late Holocene, especially in the Andes, Pacific Coast and western South America. The partially discontinuous spatiotemporal pattern probably reflects variation in prevalence within and among populations. Taken together, these findings indicate that this ancestry was present during the initial peopling of America and that it may have contributed more strongly to Late Holocene and present-day genetic diversity.

We tested whether Ypykuéra-related ancestry in Indigenous Americans reflects shared ancestry with Australasians by means of archaic hominins (Neanderthals and/or Denisovans). We compared D(Mbuti, Onge; Mixe, X) with D(Mbuti, Neanderthal or Denisova; Mixe, X), where X denotes Indigenous American groups. Mixe served as a Mesoamerican reference to match earlier studies reporting Australasian affinity. No correlation was detected between Australasian and Neanderthal (Spearman’s r = −0.006, P = 0.971) or Denisovan affinity (r = −0.1002, P = 0.5372). By contrast, Neanderthal and Denisovan affinities were strongly correlated (r = 0.6572, P = 7.2 × 10^−6), consistent with homogeneous archaic ancestry in the founding populations.

An alternative hypothesis proposes that Australasian affinity reflects retention of the Ypykuéra component in isolated groups with high internal genetic similarity. Such populations and genomic regions, characterized by elevated ROH, would be less affected by admixture that could dilute signals of ancient Population Y ancestry. This hypothesis is not supported by our data, which show no correlation between Australasian affinity and inbreeding (FROH) (Spearman’s r = 0.2503; P = 0.1192). Moreover, ROH hotspots, defined as regions with ROH density greater than three standard deviations above the mean, show little overlap with loci of Australasian affinity, with only about 6% of such positions coinciding.

We tested whether Indigenous American affinity to present-day Australasians also includes ancient Hòabìnhian individuals, proposed ancestors of mainland Southeast Asian hunter-gatherers, including the Onge Using D(Mbuti, Y; Mixe, X), with Y as Onge or Hòabìnhian individuals (La368, La364) and X as Indigenous American populations, we evaluated correlations in affinity to Onge and Hòabìnhian individuals. La368 forms a sister branch to Onge, whereas La364 is modelled as Australasian-related plus Austronesian ancestry, sister to Ami. We observed significant correlations for La368 (Spearman’s r = 0.6444; P = 1.1856 × 10^−5) and La364 (Spearman’s r = 0.6208; P = 2.8848 × 10^−5). These results support a shared ancestry component between Indigenous Americans and Australasians that extends deep into the past.

The Current Biology article and its abstract:

• Expansion of ancestry into the Pampas, Uruguay, and Patagonia from the Middle Holocene

• Repeated mobility from southern Andean and southern Patagonian-related populations

• Genetic differentiation between the Upper and Lower Paraná River Delta ∼600 years ago

• Coastal dispersal from southern Brazil to eastern Uruguay via mound-builder societies

The Southern Cone represents the southernmost region of South America settled by humans. Although ancient genomes from southern Patagonia have been sequenced, genomes from the central Southern Cone (CSC) remain temporally and spatially sparse. Archaeology documents major cultural transformations during the Middle and Late Holocene, yet their relationship with demographic processes has been debated. 

We present genome-wide data from 52 individuals spanning 6,000 years, originating from four regions of the CSC in present-day Argentina and Uruguay: the central and southern Pampas, Northwest Patagonia, the Paraná River Delta and Lower Uruguay River, and the eastern lowlands of Uruguay. 

Genomic evidence from the Pampas reveals the presence of at least three distinct ancestries during the Middle Holocene. Although genetic contacts with southern Patagonian groups were sporadic, we identified the expansion of an ancestry of unknown geographic origin by 5,500 years ago (ya), which increased during the Late Holocene. This ancestry arrived in Northwest Patagonia by at least 600 ya and co-existed locally with a southern Andean genetic profile until colonial times. 

Genetic structure differentiates populations along the Paraná River Delta and Lower Uruguay River by 1,500 ya. 

Individuals from the eastern lowlands of Uruguay show genetic links with Sambaqui-associated populations from the southern coast of Brazil, suggesting the role of human dispersals in connecting tropical lowland cultural traditions. 

Our work documents the diffusion of genetically distinct groups across all studied regions and provides compelling evidence that large-scale human movements contributed to the remarkable cultural diversity of CSC populations during the Middle and Late Holocene.

Kim-Louise Krettek, et al., "The shared genomic history of Middle- to Late-Holocene populations from the Southern Cone of South America" Current Biology (April 22, 2026).