Pre-Colombian New World Admixture In Ancient Easter Island Genomes

Polynesian people reached Easter Island around 1250 CE and were the first humans there. Europeans first reached the island in 1722 CE, at which time there were 1,500 to 3,000 people living there. European diseases, Europeans killing them, and Portuguese slave traders brought the Polynesian population down to a low point of 110 people some time after the 1860s. This paper's introduction suggested that as many as 15,000 people were living on the island on its pre-European peak, but later studies and this paper suggest that this peak population was greatly overestimated. The best fit to the genetic data shows a steady but slow population increase on the island after it was settled until European first contact, and the ecological collapse theory is rejected.

About 10% of Easter Island ancestry comes from pre-Columbian admixture with the indigenous peoples of the Americas as a result of admixture events in the time period from 1250-1430 CE, with a best fit timing in the late 1300s. This date also strongly favors admixture with indigenous Americans after, and not before the ancestors for the sampled individuals arrived on Easter Island. In particular, "the Native American component in Ancient Rapanui to be most closely related to Pacific Coast South Americans and not North Americans or populations east of the Andes further substantiates trans-Pacific contacts between Polynesians and Native Americans."

This further corroborates prior evidence of pre-Columbian contact between Polynesians and the pre-Columbian peoples of the Americas, and is also consistent the with expected time frame of these contacts from prior data.

we reconstructed the genomic history of the Rapanui on the basis of 15 ancient Rapanui individuals that we radiocarbon dated (1670–1950 CE) and whole-genome sequenced (0.4–25.6×). We find that these individuals are Polynesian in origin and most closely related to present-day Rapanui, a finding that will contribute to repatriation efforts. Through effective population size reconstructions and extensive population genetics simulations, we reject a scenario involving a severe population bottleneck during the 1600s, as proposed by the ecocide theory. Furthermore, the ancient and present-day Rapanui carry similar proportions of Native American admixture (about 10%). Using a Bayesian approach integrating genetic and radiocarbon dates, we estimate that this admixture event occurred about 1250–1430 CE.

From here. The body text of the article provides some background:

several pieces of evidence suggest that Rapa Nui did not constitute the easternmost point of long sea voyages and that Polynesian peoples eventually reached the Americas before Columbus. 

Genetic studies on present-day individuals have supported such contact. Present-day Rapanui were found to harbour Native American and European admixture in their genomes. Notably, in that work, Native American admixture (dated 1280–1495 CE) was estimated to pre-date European admixture (dated 1850–1895 CE). 

More recently, Native American admixture was detected not only in present-day individuals from Rapa Nui, but also from Rapa Iti, Tahiti, Palliser, Nuku Hiva (North Marquesas), Fatu Hiva (South Marquesas) and Mangareva. In that study, the Native American gene flow in the different islanders was dated between 1150 (South Marquesas) and 1380 CE (Rapa Nui), in line with the date estimated in ref. 5. 

However, the only two ancient DNA studies of ancient Rapanui so far did not find evidence for Native American admixture. The first study focused on mitochondrial DNA from 12 individuals, whereas the second analysed low-depth (0.0004–0.0041×) whole-genome data from 5 individuals dating before and after European contact. In the latter, downstream population genetic analyses confirmed that the five ancient individuals were Polynesian. However, even though the analysed human remains were post-dating the inferred Native American admixture time, no Native American ancestry was reported in these ancient genomes, casting doubt on the findings based on data from present-day populations.

The admixture and Native American contract dates cited above are also just in the right time frame to explain the geographic distribution and lack of fixation of "Paleo-Asian" ancestry in modern South American populations, although that scarce Paleo-Asian component is very small and is seemingly not a very close match to Polynesian ancestry. 

The geographic spread and lack of fixation of the Paleo-Asian component in South America is inconsistent and irreconcilable with a time depth greater than that of the primary founding population of the Americas for that genetic ancestry component.

Highlights From The Last Year In High Energy Physics

A new fourteen page preprint summarizing results from several of the main subjects discussed at the Moriond 2024 conference has a highly concentrated wealth of results from the last year, some of which were first announced at the conference. The paper is Barbara Clerbaux, "Experimental Summary of the Moriond 2024 conference - Electroweak Interaction & Unified Theories" arXiv:2409.07120 (September 11, 2024).

This year's results generally strongly vindicate the Standard Model of Particle Physics, although there are a few minor experimental tensions with it. I summarize the results further below.

The Higgs Boson

The latest (full run 2) mass measurement from CMS and from ATLAS are mH = 125.04 ± 0.11 (stat) ± 0.05 (syst) GeV for the H→ZZ→4ℓ decay channel and mH = 125.17 ± 0.11 (stat) ± 0.09 (syst) GeV for the H→γγ decay channel, respectively, the main uncertainties coming from the lepton and photon energy scales. Figure 1 presents the various H mass measurements of ATLAS and the final run 1 and run 2 combination, leading to a relative precision of 0.09%. The H mass uncertainty target for the HL-LHC is about 20 MeV. 

The tiny width predicted in the SM of 4.1 MeV is much smaller than the experimental mass resolution of about 1 to 2 GeV. However BSM contributions could bring a significant enhancement of the H width. ATLAS and CMS deduced an indirect limit on the H width using the ratio of the off-shell and on-shell cross section measurements. 

Various other measurements of Higgs boson decays and couplings are basically consistent with the Standard Model predictions for those properties.  

A wide scope of new BSM H boson searches has been released by ATLAS and CMS. No excess are observed above the SM prediction, however still a large amount of phase space is available for extended H sectors. In the search for low mass H→γγ, CMS observes an excess of local (global) significance of 2.9σ (1.3σ) at a mass of 95.4 GeV, ATLAS observes a local significance of 1.7σ at 95.4 GeV. 

The 95.4 GeV excess is not statistically significant globally, or in the combined CMS and ATLAS measurements. Notably, the bump that is observed is very close to the mass of the Z boson, which is 91.188(2) GeV plus the mass of the b quark which is 4.183(7) GeV (according the latest Particle Data Group estimate), the sum of which is 95.371(7) GeV, which to three significant digits is 95.4 GeV. 

Since a bb decay is the most common form of Higgs boson decay, and Z boson-photon decays are also possible, one possibility, for example, is that this bump represents the decays of a real and a virtual Higgs boson pair in which one of the b quark decay products and a photon are missed by the LHC detectors and misinterpreted in the subsequent analysis.

The Electroweak Precision Results

The W mass is extracted from the W boson transverse mass and pT distributions. The obtained value, mW = 80366.5 ± 15.9 MeV, has an impressive precision of less than 0.02%. The W mass result, shown in Figure 4 (left) is in good agreement with the SM and does not confirm the higher value of the W mass obtained in 2022 by the CDF data re-analysis measurement. The ATLAS analysis is also sensitive to the W width, measured to be ΓW =2202±47 MeV. ATLAS performed a comprehensive study of events with jets and large missing transverse energy (MET) in the final state, providing a measurement of the differential Z→ ν¯ ν cross section as a function of the Z boson pT. The W mass is also measured by LHCb with uncertainties that are anti-correlated to that of ATLAS and CMS. Using about a third of the available run 2 dataset, the value of mW = 80354±32 MeV is obtained by LHCb, with the target to have an expected statistical precision with the full run 2 dataset of about 14 MeV. . . . 

The sin2θℓ eff measurement is a CMS highlighted new result presented at the conference. The mixing angle sin2θℓ eff is a key parameter of the SM and is calculated using other precise experimental inputs to be sin2θℓeff(SM)=0.23155±0.00004. Up to now the most precise measurements come from LEP and SLD, and differ between each other by about 3σ. The new CMS analysis uses the Drell-Yan events with electron or muon pairs in the final state. In case of the electron channel, the very forward calorimeters up to a pseudorapidity value of |η| = 4.36 are added in the event selection, increasing significantly the measurement precision of the forward-backward asymmetry in the lepton decay angle. From this, a value of sin2 θℓ eff=0.23157±0.00031 is extracted, reaching a comparable precision as the LEP and SLD measurements, as shown in Figure 4 (right). . . .

The test of lepton flavour universality (LFU) in W decays is the highlighted new result by ATLAS. The analysis uses the top-quark pair events and compares the occurrence of W decays in the muon and the electron final states. To reduce as much as possible the systematics uncertainties, the ratio R = BR(W→µν)/ BR(W→eν) is measured and normalised to the corresponding ratio for the Z boson BR(Z→µµ)/ BR(Z→ee). The ratio R obtained is presented in Figure 5(left), the value is in agreement with 1 with a relative uncertainty of 0.45%. This is the most precise single measurement for this ratio to date and is also more precise than the previous PDG (particle data group) average. 

The photon-induced production of a pair of tau leptons is observed for the first time in proton-proton collisions by CMS at 5.3σ. . . . Modifying the tau lepton magnetic moment modifies the γγ → ττ cross section and modifies the pT and mass distributions of the signal. A very precise measurement of the tau lepton anomalous magnetic moment is extracted and presented in Figure 5(right), in good agreement with the expected SM value given as the dashed vertical line. The measurement does not show evidence for the presence of new physics that would modify its value. 

Top Quark Physics 

Measurements of top quark properties have been reported by ATLAS and CMS. . . . A new combination of the ATLAS and CMS top quark mass measurements leads to mt = 172.52 ± 0.14 (stat) ± 0.30 (syst) GeV, the dominant systematics uncertainty coming from the b-quark jet energy scale. . . . The ttZ+tWZ cross section measurement has a small tension with the SM prediction (being slightly above at a 2σ level). The new ATLAS result on the t¯ tγ production is in agreement with the SM. 

Quantum entanglement in top events are new results that generated excitement and discussion during the conference. ATLAS and CMS presented their latest analysis results from top-antitop events in the dilepton decay channels. Top-quark pairs at the LHC are mainly unpolarised, with their spins being strongly correlated. The spin information can be measured via the final state particle angular variables. The spin correlation depends on the mass of the top-antitop system mt¯t and on the angular variables. A system is considered as being in a quantum entanglement state if D < −1/3, where D is defined as the trace of the spin correlation matrix divided by 3. . .  .  entanglement is observed with > 5σ at low mt¯t. The CMS analysis shows in addition that when a t¯t bound state (toponium, a colour singlet pseudo-scalar state) is included in the simulation, the agreement between the measurement and the SM simulations improves in the threshold mass region.

Beyond The Standard Model Physics 

[N]o deviation from the SM expectation has been observed[.]

Flavor Physics

The LHCb and CMS experiments made measurements of CP violation in b quark and charm quark decays that increase the precision with which the CP violating parameter in the CKM matrix has been measured.

The LHCb and Belle/Belle II experiments looked at lepton flavor universality violations in semi-leptonic decays of b quarks to charm quarks, in results that put the global average measurement in mild tension with the Standard Model prediction of lepton flavor universality (at a 3.2 sigma level). The great spread of the experimental results, however, casts doubt on the meaningfulness of a global average measurement.

Belle/Belle II improved the accuracy with which the branching fractions of ten kinds of B meson decays and measured the branching fractions of four more kinds of B meson decays for the first time.  

BESIII mostly measured charmed hadron decays, improving the precision with which the CKM matrix element for charm to strange quark transition probability is known and examining the possibility of lepton flavor universality violations:

Using this measurement together with input from lattice QCD calculation, the CKM matrix element |Vcs| is determined with a precision of 1.4%. When combined with the tau decay channel analysis, the precision on |Vcs| value improves to 1.0%. Lepton flavour universality tests have also been performed in leponic and semi-leptonic decays of charm mesons. No violation was observed at the 1.5% precision level.

Neutrino Physics

Multiple experiments including NOvA, T2K, and Super-Kamiokande studied neutrino oscillation parameters. The precision of the measurement of the mass difference between the second and third neutrino mass eigenstates was improved. A normal mass ordering is favored, but only inconclusively. CP violation in neutrino oscillations has also been largely confirmed, but its magnitude has large uncertainties.

Efforts to detect neutrinoless double-beta (0νββ) at the CUORE and Legend experiments continued to come up empty, increasing the minimum half-life for neutrinoless double-beta decay. At CUORE:

The limit obtained for the half-live time of 130Te, based on data taken from 2017-2023 . . . is T1/2 0ν > 3.8 x 10^25 yr at 90% CL, which is the most stringent limit for the 130Te to date. The corresponding limit on the effective Majorana mass assuming a light Majorana neutrino-exchange is mββ < 70-240 meV. 

The Legend experiment using enriched germanium detector 76Ge has a . . . ultimate goal is to reach sensitivity for a half-life time of this nucleus beyond 10^28 years, corresponding to a neutrino effective mass measurement of about 18 meV.

Neutrinoless double beta decay, if discovered, would be strong evidence that the neutrino is a Majorana particle with Majorana mass, and would represent the first evidence of non-conservation of lepton number ever observed. But, given the increasing evidence that the neutrino masses are masses are very small, with the lightest neutrino mass probably well under 18 meV, we shouldn't expect to be able to detect neutrinoless double beta decay in the near to medium term, even if neutrinos do have Majorana mass.

The Faser experiment at the LHC has as its goal: 

to measure SM neutrino interaction cross sections at unexplored TeV energies, as well as to search for long-lived BSM particles (e.g. axion-like particles ALPs). . . . New results were presented on neutrino (νe and νµ) interaction cross sections. . . . This represents the first detection of νe at the LHC. Results on limits on ALPs were also shown for a luminosity of 57.7 fb−1, excluding uncovered parameter space (in the coupling and mass plane) significantly. . . . 

The present neutrino mass limit of 0.8 eV from the Katrin experiment was reminded and the future release of the neutrino mass limit with 0.5 eV sensitivity expected for mid-2024 was presented, together with the R&D for the Katrin++ project to reach the inverted ordering mass scale.

The Katrin result is now outdated as previously reported at this blog. The new limit is actually 0.45 eV.

An interesting (small) deficit of events was observed by the IceCube experiment in the muon antineutrino survival probability for atmospheric neutrinos, that can be fitted with the addition of a fourth neutrino family (the p-value for the null hypothesis is 3.1%). 

The potentially anomalous IceCube results have been credibly explained as the result of flawed modeling. See also this July 2024 paper reaching a contrary conclusion.

Dark Matter Searches

Searches for dark matter (DM) by the Lux-Zeplin experiment at the Sanford Underground Research Facility and by the PandaX experiment at the China Jinping Underground Laboratory were reported.

None of the experiments detected any dark matter and the parameter space excluded by these direct dark matter detection experiments was expanded.

Muon g-2

Updates on anomalous magnetic moment of the muon defined as aµ = (gµ −2)/2 were also discussed. It is a very sensitive variable to new physics, as the quantum effects arise from virtual particle contributions from all known and potentially unknown particles. The long-standing discrepancy between the experimental measurements and the theory predictions has been scrutinised during the conference. The Fermilab Muon g-2 experiment is providing improved measurements, currently at a precision of 0.2 ppm. A lot of efforts are dedicated to the SM calculation, and more specifically on the hadronic vacuum polarisation contribution. New results on lattice QCD have been presented and when taken into account, the SM prediction for aµ falls better in line with the experimental results. However these computations are complicated, and lattice QCD results from other groups are expected to be public soon. A discussion will then take place on the inclusion or not of these results in the official SM calculation.

As mentioned in previous posts on the determination of the SM prediction for muon g-2, it is actually pretty clear that the experimental results confirm the SM prediction, and that the previously anomaly was a result of inaccurate experimental data that was used to substitute for some particular difficult Lattice QCD calculations. 

The Voynich Manuscript Is Not A Hoax

Image via Wikipedia

A post at Language Log explains how multispectral imaging from ten years ago (which was just recently released due to the efforts of a determined blogger) reveal that the Voynich Manuscript, an illustrated vaguely alchemical and astrological handwritten tome in an indecipherable code, probably written around 1425 CE, is not a hoax or fake. 

Claimed efforts to decipher it have likewise flopped.

CODATA Physical Constants Updated

CODATA is one of the global standards for measurements of physical constants (fundamental and otherwise). The 2022 update is now available at arXiv with commentary on how the values were established.

The 2026 CODATA adjustment of the fundamental constants is the next regularly scheduled adjustment. Data being used in this adjustment is required to have been discussed in a publication preprint or a publication prior to 31 December 2026.

The muon g-2 discussion in the preprint is already outdated (in part by design, as it is only considering papers before December 31, 2022).

The Muon g-2 Issue In A Nutshell

The introduction of a new paper by authors who describe themselves by the first initials of their surnames (KNTW) nicely sums of the state of the efforts to compare experimental measurements of muon g-2 with predictions of its value using the Standard Model of Particle Physics.

The anomalous magnetic moment of the muon, aµ, and its potential for discovering new physics stand at a crossroads. The accuracy and precision of the Standard Model (SM) prediction, a(SM)µ, relies on resolving significant tensions in evaluations of the hadronic vacuum polarization (HVP) contributions, a(HVP)µ . Data-driven evaluations of the HVP using e+e− → hadrons cross section data as input result in a value for a(SM)µ that is ∼ 5σ below the most recent experimental measurement from the Muon g−2 Experiment at Fermilab, a(exp)µ. With an unprecedented 200 parts-per-billion (ppb) precision, confirmation of previous measurements, and final results (expected in 2025) projected to improve the experimental precision by another factor of two, the measurements of aµ appear to be on solid ground.<1> However, high-precision lattice QCD calculations (incorporating QED corrections) and the most recent experimental measurement of the dominant e+e− → π+π− cross section from the CMD-3 experiment result in independent, but consistent values for aHVP that are >4σ larger than previous data-driven evaluations. They therefore generate values for a(SM)µ that are consistent with a(exp)µ and support a no-new-physics scenario in the muon g−2, whilst leaving an unexplained discrepancy with the vast catalogue of previously measured hadronic cross section data. 

The KNT (now KNTW) data-driven determinations of a(HVP)µ are crucial inputs to previous and future community-approved predictions for a(SM)µ from the Muon g−2 Theory Initiative. With multiple, independent lattice QCD evaluations of a(HVP)µ becoming significantly competitive only in recent years, it was one of only a few data-driven HVP evaluations which exclusively formed the value for a(HVP) lattice QCD and updated data-driven evaluations, with KNTW being a key input to the latter. An alternative approach to determine a(HVP)µ by experimentally measuring the spacelike vacuum polarization is under preparation at the MUonE Experiment. 

The KNTW procedure for evaluating the total hadronic cross section and a(HVP)µ (plus other precision observables which depend on hadronic effects) is undergoing a major overhaul and modernization of the analysis framework. The aim of this revamp is to make use of sophisticated analysis tools, perform new evaluations of various contributions, incorporate handles in the analysis structure that result in flexible and robust ways to test various systematic effects, improve determinations of corresponding systematic uncertainties and ultimately produce a new state-of-the-art in the determination of these quantities. These changes will be described in detail in the next full KNTW update. 

Such future data-driven evaluations of a(HVP)µ depend largely on new experimentally measured hadronic cross section data, particularly for the π+π− final state. These require increased precision and a more robust understanding of higher-order radiative corrections, which are currently being studied in detail within the STRONG2020 program and The RadioMonteCarlow 2 Effort. Whilst a discussion of these improvements is outside the scope of this letter, such future results have been announced from the BaBar, Belle II, BESIII, CMD-3, KLOE and SND experiments within the next few years. These new measurements could either fundamentally adjust the previous data-driven evaluations of a(HVP)µ used in the SM prediction that exhibits the ∼ 5σ discrepancy with a(exp)µ. Future SM predictions are expected to incorporate both to bring them more in line with e.g. the recent CMD-3 π+π− measurement or make the current tensions even worse if new measurements confirm lower cross section values with increased precision. 

Importantly, and as will be discussed in the next section, analysis choices in how to use these data can produce significantly different results. With this being the case, the future of a(HVP)µ and a(SM)µ being so uncertain, and the crossroads in the current tensions ultimately suggesting either a discovery of new physics or a multi-method confirmation of the SM, analysis blinding for data-driven determinations of the HVP is now paramount. 

<1> Alternative future measurements of aµ are also planned at JPARC and PSI.

Unification In Physics Doesn't Work

This figure was the classic illustration of force unification, although it turns out that unification doesn't happen, even under SUSY, with the constraints of recent high precision coupling constant measurements.

Woit at his "Not Even Wrong" blog shares some slides he did for a podcast on grand unified theories of physics, which try to combine the three forces of the Standard Model into a facets of a single force, typically within a single Lie group, rather than the SU(3) x SU(2) x U(1) of the Standard Model. He explains that:

The main goal of the slides is to explain the failure of the general paradigm of unification that we have now lived with for 50 years, which involves adding a large number of extra degrees of freedom to the Standard Model. All examples of this paradigm fail due to two factors: 

• The lack of any experimental evidence for these new degrees of freedom.  

• Whatever you get from new symmetries carried by the extra degrees of freedom is lost by the fact that you have to introduce new ad hoc structure to explain why you don’t see them.

Afghanistan, Once Upon A Time

There was a Greek kingdom in Afghanistan and surrounding parts of Central Asia, called the Greco-Bactrian Kingdom, for roughly 136 years from 256 BCE until 120 BCE.