A New Measurement Of The Neutron Mean Lifetime

Background

There are two methods that have been used historically to measure the mean lifetime of a free neutron: the beam method and the storage method.

The beam method measures neutron lifetime by counting the injected neutron and decay product in the beam.

The storage method measures neutron lifetime by storing ultracold neutron in the specific bottle. They count the number of surviving neutrons S(1) and S(2) after distinct storing times t(1) and t(2).

The global average mean lifetime of a free neutron by the beam method is 

888.0 ± 2.0 seconds.

The global average mean lifetime of a free neutron by the storage method is 

879.4 ± 0.6 seconds

There is an 8.6 second (4.1 standard deviation) discrepancy between results from the two measurement methods, which is huge for fundamental physics in both absolute terms and relative to the amount of uncertainty in the respective measurements. 

The New Measurement

A new measurement by a third method has been done at the Japanese J-PARC experiment using pulsed neutron beams. The mean lifetime of a free neutron by this method is:

898 ± 10 (statistical) + 15 -18 (systemic) seconds 

for a combined error of 

898 + 18 - 20.6 seconds 

which dumbed down to a single number is 

898 ± 19.3 seconds

Due to the high uncertainty of the new measurement it is consistent with both the prior beam method and storage method results at the two sigma level, although it tends to favor the less precise beam method result.

Commentary

The neutron was discovered in 1932 and the lifetime of a free neutron was first measured in 1951. Seventy years later, the U.S. National Institution of Standard and Technology is working on the problem and hasn't made much progress.

The neutron is, by far, the longest lived subatomic particle that is not actually stable. Its mean lifetime is a little less than fifteen minutes. The runners up, the fundamental particle known as the muon and the composite meson known as the pion, have mean lifetimes on the order of a microsecond, which is almost a billion times shorter. Of course, embedded in stable atoms, bound neutrons are dynamically stable. In lattice QCD models calibrated to only modestly heavier than physical pion masses, dineutrons without protons are also stable.

Neutrons are not exactly exotic. One 1/7th of the ordinary matter in the universe is made up of them. They are found in Nature and not just ephemerally in particle colliders. Other properties of neutrons have been measured to great precision. We know the mass of a neutron to one part per two billion. And, the only subatomic composite particle whose internal structure is better understood is the proton.

The free neutron mean lifetime is an important experimentally measured physical constant for a variety of theoretical and practical purposes. It contributes to the determination of a couple of standard model of particle physics constants (a CKM matrix parameter and the weak force coupling constant). It is important in nuclear physics. It is important in Big Bang Nucleosynthesis calculations. But those independent indirect measurements of the neutron mean lifetime aren't sufficiently precise to definitively resolve the discrepancy. 

Similarly, a prediction from the Brookhaven National Laboratory of the value based on quantum chromodynamics as of 2018 is still not sufficiently precise to support one over the other.

The scientists have already used the new nucleon axial coupling calculation to derive a purely theoretical prediction of the lifetime of the neutron. Right now, this new value is consistent with the results from both types of experimental measurement, which differ by a mere 9 seconds. “We have a number for the neutron lifetime: 14 minutes and 40 seconds with an error bar of 14 seconds. That is right in the middle of the values measured by the two types of experiments, with an error bar that is big and overlaps both,” [Enrico Rinaldi, a special postdoctoral researcher at the RIKEN BNL Research Center at DOE’s Brookhaven National Laboratory, who was involved in developing simulations essential to the new calculation] said.

Yet, this particular physical constant turns out to be really hard to measure, in part, because neutrons do not have net electromagnetic charge that assists in measuring other particles. 

We can measure the time that it takes an athlete to complete a 100 meter dash with human controlled stopwatches to an order of magnitude or two greater precision in absolute terms. A discrepancy of 1% between two different methods of measuring the constant is awful for a constant that is so commonplace, so macroscopic, and so important.

For all of those reasons, the widely held consensus is that he discrepancy comes from unconsidered systematic error, rather than from beyond the Standard Model physics. A March 2020 pre-print reflects the conventional wisdom on the matter, which favors the more precise storage method measurement, stating in its abstract that:

This article discusses the possible causes of discrepancy in the measurements of the neutron lifetime with beam method experiment. The most probable cause, apparently, is the loss of protons in beam method experiment during storage in a magnetic trap due to charge exchange collisions of protons with the residual gas. The proton becomes neutral and leaves the trap, which leads to a decrease in the number of registered protons, i.e. to a decrease in the probability of neutron decay or to an increase in the measured neutron lifetime.

But the fifteen year old discrepancy has still not been satisfactorily resolved.

The Paper

The paper and its abstract are as follows:

A neutron decays into a proton, an electron, and an anti-neutrino through the beta-decay process. The decay lifetime (∼880 s) is an important parameter in the weak interaction. For example, the neutron lifetime is a parameter used to determine the |Vud| parameter of the CKM quark mixing matrix. The lifetime is also one of the input parameters for the Big Bang Nucleosynthesis, which predicts light element synthesis in the early universe. 

However, experimental measurements of the neutron lifetime today are significantly different (8.4 s or 4.0σ) depending on the methods. One is a bottle method measuring surviving neutron in the neutron storage bottle. The other is a beam method measuring neutron beam flux and neutron decay rate in the detector. There is a discussion that the discrepancy comes from unconsidered systematic error or undetectable decay mode, such as dark decay. 

A new type of beam experiment is performed at the BL05 MLF J-PARC. This experiment measured neutron flux and decay rate simultaneously with a time projection chamber using a pulsed neutron beam. We will present the world situation of neutron lifetime and the latest results at J-PARC.

N. Sumi, et al., "Precise Neutron Lifetime Measurement Using Pulsed Neutron Beams at J-PARC" Proceedings of J-PARC Symposium 2019 arXiv:2102.09758 (February 19, 2021).

Another Anomaly Bites The Dust (Not A Muon g-2 Experiment Blog Post)

Background

In modern physics, experimental anomalies are almost always due to boring methodological issues, rather than "new physics." This case is no exception. 

(Also, for physics fans who aren't paying close attention, this IS NOT the big muon g-2 experiment result paper that everyone in the high energy physics world has been waiting for for the past fifteen years. That paper is due out about one to six weeks from now.)

Lots of anomalous experimental results show up involving muons, in part, because the reveal with the hard certainty of experimental measurements, flaws in previous work done with electrons which due to their lower mass are often much less precise.

The Cosmic Ray Muon Excess Anomaly

One such anomaly had been an apparently excess of muons in the debris showers of high energy cosmic rays (which, despite the misleading name, are mostly very fast moving microscopic particles of matter rather than photons). Scientists have been seeing 10-100% more muons than predicted by their Standard Model physics motivated models in the fallout from ultrahigh energy cosmic rays (in other words there is a deficit in the number of muons predicted in simulations).

A new paper from a large collaboration of scientists, however, establishes that the muon excess was illusory and mostly flowed from a small but accumulating error in the number of muons predicted to be present in simulations used to established the predicted number of muons, rather than experimental error or new physics.

So, another intriguing anomaly that might have pointed to beyond the Standard Model physics has disappeared.

Significance

In a nutshell, this matters a lot because it implies that there are probably no new high energy physics phenomena beyond the Standard Model of Particle Physics at energy scales far beyond those we have any hope of probing a new particle colliders in our lifetimes, or even in the lifetimes of our great grandchildren.

It tends to confirm that we have entered a large range of energy scales in which there is a new physics "desert". 

We are very likely in what high energy physics experimentalists sometimes call "the nightmare scenario" in which there is nothing new out there in terms of fundamental physics for them to discover in the course of their careers. 

Sure, they can measure physical constants with greater precision and explore the precisely way that ephemeral exotic particles that form only at extremely high energies form and decay in ways that are profoundly difficult to calculate from first principles. But if we are in the nightmare scenario, then the basic laws of physics formulated in the late 1970s and early 1980s are all that is out there that we have any ability to observe for the foreseeable future.

We may be entering a period in high energy physics akin to the period in the physics of gravity and the laws of motion between 1687 when Newton formulated the law of gravity and law basic laws of classical mechanics in physics, and the second decade of the 20th century when General Relativity, Special Relativity and quantum mechanics were developed (Einstein played a pivotal role in all three of these developments, by the way), about 230 years later, or the roughly 50 years between the development of Maxwell's equations in 1862, and the formulation of quantum mechanics, in the physics of electromagnetism (those two fields combined were the whole of fundamental physics at the dawn of the 20th century).

In contrast, we are quite unlikely to be in the period of flourishing scientific advancement from about 1912 to about 2012 (when the Higgs boson was discovered) that marked the development of Special Relativity, General Relativity, quantum physics, the physics of the strong and weak forces, and modern cosmology (although prospects for break throughs in understanding dark matter and dark energy phenomena in the next two or three decades, and in the "non-fundamental" physics of complex systems, are much brighter than the prospects of new high energy physics at energy scales we can probe with experiments and astronomy observations).

The Large Hadron Collider is the most powerful controlled high energy physics experiment in the world of all time. The peak energies of the events that it studies are on the order of 10^13 eV (10 TeV). The multi-billion dollar colliders that scientists are considering building for the next generation of high energy physics experiments would have peak energies on the order of 10^14 eV (100 TeV).

An ultra high energy cosmic ray produced naturally by massive stars and black holes elsewhere in the Universe that happen to end up in our atmosphere, by definition, have energies of at least 10^18 eV (1,000,000 TeV), about 100,000 times more energy than the most energetic interactions at the LHC and about 10,000 times more energy than the most energetic interactions expected at a next generation particle collider.

If the Standard Model of Particle Physics is flawed in some way that needs to be explained by new physics beyond the Standard Model in slight ways at energies ten times what we have observed at particle colliders so far, these deviations from the Standard Model expectation ought to be much greater at energies 100,000 times what we have observed at particle colliders so far.

Ultra high energy cosmic ray decay observations don't actually increase our power to detect beyond the Standard Model physics by a full five orders of magnitude, because the precision available to us when we observe these natural experiments that can unfold anywhere in the sky with no advanced notice is not nearly as great as what we can observe in the exquisitely controlled, calibrated, and timed events in a particle collider like the LHC, that we can repeat in almost precisely the same way, over and over and over again.

But observations of Ultra High Energy Cosmic Ray decays still give us low resolution access to vastly higher energy regimes than anything we could observe in a man made particle collider in the foreseeable future. 

To the extent that these observations confirm the Standard Model expectations up to a given magnitude of uncertainty when the "wild" events that we can observe is modeled correctly (uncertainties on the order of low single digit percent errors in relative terms), we know that any new physics that could be observed at a future collider have to be smaller than that, after scaling down any proposed tweak to the Standard Model for the effects that would be expected at energy scales 10,000 times smaller.

In particular, results like this one put a huge damper on "just around the corner" predictions for phenomena like new supersymmetric particles at energies of tens or hundreds of TeV in mass, which are legion in the supersymmetry phenomenology literature.

New fundamental particles with masses in the 10,000 TeV or less, and certainly new fundamental particles with masses of 100 TeV or less that might be seen at next generation collider, would almost surely cause the decays of Ultra High Energy Cosmic Rays in Earth's atmosphere to look dramatically different than the Standard Model of Particle Physics predictions which this latest paper instead, tends to confirm.

If one is a Bayesian statistician trying to develop a statistical prior expectation for the probability of finding new physics at a next generation particle collider, this result is almost as important as the new muon anomalous magnetic moment (muon g-2) measurement expected next month.

Both measurements are very general global tests of new physics at energies well beyond the 10^13 eV energies that can be measured at the LHC, but also well below the GUT (grand unified theory) scale of about 10^25 eV which would have existed in the Universe only at the very earliest moments immediately after the Big Bang.  Neither muon g-2 nor Ultra High Energy Cosmic Ray decays can probe physics at the near GUT scale because new physics at those extreme high energies can "decouple" from a "low" energy effective theory like the Standard Model that can actually be probed with experimental evidence and astronomy observations.

Both muon g-2 anomalies and Ultra High Energy Cosmic Ray decay anomalies can tell us (1) if there are any high energy new physics out there (subject to loopholes for multiple kinds of new physics at high energies that exactly cancel each other out in both of these global measures of new physics), and (2) the approximate magnitude of any new physics that we are missing in a global sense if we see anomalies in these observations. 

But because they are global measures influenced by almost all aspects of the Standard Model, if we do see an anomaly, neither of these observations will tell us much about what is causing it. Also the magnitude of an anomaly does not even tell us the absolute magnitude of the new physics we are looking for. Small new physics effects at just around the corner energies would create the same kind of signal as big new physics effects at much higher energies.

The fact that this new study was able to show that muon excesses got more pronounced at each lower energy scale that could be observed was the big tipoff that the cosmic ray muon excess was a product of cumulative error in each iteration of the simulations that were done, rather than actual new physics, which would have been pronounced at higher energies while not getting much bigger at lower energies whose behavior is better understood because it is within, or is closer to, the energy scales that we have already probed with high precision in particle colliders.

The Paper

The paper and its abstract are as follows:

We present the first measurement of the fluctuations in the number of muons in extensive air showers produced by ultra-high energy cosmic rays. We find that the measured fluctuations are in good agreement with predictions from air shower simulations. 

This observation provides new insights into the origin of the previously reported deficit of muons in air shower simulations and constrains models of hadronic interactions at ultra-high energies. Our measurement is compatible with the muon deficit originating from small deviations in the predictions from hadronic interaction models of particle production that accumulate as the showers develop.

The Pierre Auger Collaboration, "Measurement of the fluctuations in the number of muons in extensive air showers with the Pierre Auger Observatory" Accepted for publication in PRL arXiv:2102.07797 [hep-ex] (February 15, 2021).

The introduction from the body text of the paper provides  context for its conclusions that the excess of muons detected relative to the predicted number is due to a flaw in the simulations used to determine the predicted number of muons rather than a flaw in the experimental measurement of the muons created by ultra high energy cosmic rays, or beyond the Standard Model physics.

Ultra High Energy Cosmic Rays (UHECRs) are particles coming from outer space, with energies exceeding 10^18 eV. They provide the only experimental opportunity to explore particle physics beyond energies reachable by Earth-based accelerators, which go up to cosmic ray energies of 9 × 10^16 eV. 

The Pierre Auger Observatory detects extensive air showers that are initiated by the UHECRs colliding with the nuclei in the atmosphere. Information about UHECRs is extracted using simulations based on hadronic interaction models which rely on extrapolations of accelerator measurements to unexplored regions of phase space, most notably the forward and highest-energy region. In addition, accelerator experiments at the highest energies either probe the interactions between protons or of protons with heavy nuclei, while most interactions within air showers are between pions and light nuclei. 

A further challenge is that the UHECR mass has to be measured despite not being yet completely decoupled from the hadronic uncertainties. The observable with the least dependence on hadronic interactions is the atmospheric depth at which the longitudinal development of the electromagnetic (EM) component of the shower reaches the maximum number of particles, namely Xmax.

In hadronic cascades the energy of each interacting particle is distributed among the secondaries, mostly pions. Neutral pions rapidly decay into two photons feeding a practically decoupled electromagnetic cascade (other resonances decaying into πº’s, electrons and or photons also contribute). Charged pions (and other long lived mesons like kaons) tend to further interact until their individual energies are below a critical value, below which they are more likely to decay. 

Muons, which are products of hadronic decays, are thus predominantly produced in the final shower stages. In sufficiently inclined showers, the pure EM component is absorbed in the atmosphere and the particles that reach the ground (muons and muon decay products) directly sample the muon content, reflecting the hadronic component of the shower. 

Air showers are mainly detected at the Pierre Auger Observatory by the Surface Detector (SD), an array of water-Cherenkov detector stations, and the Fluorescence Detector (FD) consisting of 24 fluorescence telescopes. By selecting the sub-sample of events reconstructed with both the SD and the FD and with zenith angles exceeding 62º, both the muon content and the energy of the shower are simultaneously measured. 

The results obtained indicate that all the simulations underestimate the number of muons in the showers. 

These analyses come with the caveat that they cannot distinguish a muon rescaling from a shift in the absolute energy scale of the FD measurement. However, muon content and energy scale were disentangled in a complementary technique based on showers with zenith angles below 60º. Using the longitudinal profile of the shower in the atmosphere obtained with the FD and the signals at the ground measured with the SD, it was shown that the muonic component still has to be scaled up to match observed data, while no rescaling of the EM component and the FD energy is required. The measurements with the FD also show that both the position of the shower maximum in the atmosphere (Xmax) and the entire shape of the EM shower are well described by the simulations.

At lower energies, down to ∼ 10^17.3 eV, in a measurement using the sub-array of buried scintillators of the Pierre Auger Observatory, a direct count of the muons independent of EM contamination was obtained, which also shows that simulations produce too few muons. 

There is much evidence that all the simulations underpredict the average number of muons in the showers: a comprehensive study of muon number measurements made with different experiments has shown that the muon deficit in simulations starts around ∼ 10^16 eV and steadily increases with energy. Depending on model and experiment, the deficit at ∼ 10^20 eV ranges between tens of percent up to a factor of two. 

The increased statistics obtained at the Pierre Auger Observatory allows us to now take a further step and explore fluctuations in the number of muons between showers, hereinafter referred to as physical fluctuations. The ratio of the physical fluctuations to the average number of muons (relative fluctuations) has been shown to be mostly dominated by the first interaction, rather than the lower energy interactions deeper in the shower development. Here, we exploit the sensitivity of fluctuations to the first-interaction to explore hadronic interactions well above the energies achievable in accelerator experiments.

The paper concludes with the following summary of the study's results:

We have presented for the first time a measurement of the fluctuations in the number of muons in inclined air showers, as a function of the UHECR primary energy. Within the current uncertainties, the relative fluctuations show no discrepancy with respect to the expectation from current high-energy hadronic interaction models and the composition taken from Xmax measurements. 

This agreement between models and data for the fluctuations, combined with the significant deficit in the predicted total number of muons, points to the origin of the models’ muon deficit being a small deficit at every stage of the shower which accumulates along the shower development, rather than a discrepancy in the first interaction. Adjustments to models to address the current muon deficit, must therefore not alter the predicted relative fluctuations.  

Sheela na gig

Attitudes towards proper church decorations have evolved over time.

Sheela na gig is the name given to carvings of naked women displaying an exaggerated vulva. Such carvings appear on many churches in Ireland and elsewhere in Western Europe (but mainly in Ireland).

From here with a fully version of the story. Wikipedia provides background on the phenomena itself.

The distribution corresponds more or less with Celtic Europe and before that with areas having strong Bell Beaker cultural influence. But the timing, in the Medieval Period, first appearing around the 11th century CE in Christian churches, complicates a straightforward connection between these images and Celtic or Bell Beaker pagan traditions. 

So too does the fact that they appear to have originated in France and Spain and began to appear in the British Isles only in the wake of the Norman Conquest (of 1066 CE) in areas that had been subjected to Norman rule, reaching Ireland, where they became most common, last of all in the 12th century, with "areas that remained 'native Irish' have few sheela na gigs" according to the source cited by the Wikipedia article.

The phenomena arises around Y1K, which is also around the time of the early Crusades, in which the Normans were prominent participants. 

It was a time of great Viking activity over vast distances. Harald Hardrada may have died in England trying to become king of that nation, but he served for a time in the Varangian Guards in Constantinople. His connections to Kievan Rus were such that priests in the Eastern Christian tradition were brought in to aid in the conversion of Norway, which was one of the last of the places to convert to Christianity made their conversion. In Norway, "the Urnes stave church, thought to be the oldest one still in existence" was built using timber from 1069 and 1070. 

Fishing Is Like Farming

The first sedentary complex societies, which arose before domestication made farming and herding possible, were societies based upon food production through fishing. They had more in common with the farmers that would come to be than with terrestrial hunter-gatherers.

The linked article explores one such indigenous society based upon an ethnographic account of a 16th century kingdom in a fishing society in what is now Florida.

Einsteinium Somewhat Weird

Scientists predicted the existence of Einsteinium which otherwise would have left a gap at element 99 in the periodic table of elements, and predicted the properties it would have. It was first discovered in 1952 in the debris of the first hydrogen bomb. But since it doesn't occur in nature in any meaningful amounts it has been hard to actually measure its properties.

Now scientists have done that.  And, while its properties were mostly what chemists would have expected, there have been some surprises.

The researchers were able to measure a bond distance with einsteinium and also discovered some physical chemistry behavior that was different from what would be expected from the actinide series, which are the elements on the bottom row of the periodic table.

"Determining the bond distance may not sound interesting, but it's the first thing you would want to know about how a metal binds to other molecules. What kind of chemical interaction is this element going to have with other atoms and molecules?" [Berkeley Lab scientist Rebecca] Abergel said. . . . 

"Similar to the latest elements that were discovered in the past 10 years, like tennessine, which used a berkelium target, if you were to be able to isolate enough pure einsteinium to make a target, you could start looking for other elements and get closer to the (theorized)island of stability," where nuclear physicists have predicted isotopes may have half-lives of minutes or even days, instead of the microsecond or less half-lives that are common in the superheavy elements.

The paper and its abstract are as follows:

The transplutonium elements (atomic numbers 95–103) are a group of metals that lie at the edge of the periodic table. As a result, the patterns and trends used to predict and control the physics and chemistry for transition metals, main-group elements and lanthanides are less applicable to transplutonium elements. Furthermore, understanding the properties of these heavy elements has been restricted by their scarcity and radioactivity. This is especially true for einsteinium (Es), the heaviest element on the periodic table that can currently be generated in quantities sufficient to enable classical macroscale studies. 

Here we characterize a coordination complex of einsteinium, using less than 200 nanograms of 254Es (with half-life of 275.7(5) days), with an organic hydroxypyridinone-based chelating ligand. X-ray absorption spectroscopic and structural studies are used to determine the energy of the L3-edge and a bond distance of einsteinium. Photophysical measurements show antenna sensitization of EsIII luminescence; they also reveal a hypsochromic shift on metal complexation, which had not previously been observed in lower-atomic-number actinide elements. These findings are indicative of an intermediate spin–orbit coupling scheme in which j–j coupling (whereby single-electron orbital angular momentum and spin are first coupled to form a total angular momentum, j) prevails over Russell–Saunders coupling. Together with previous actinide complexation studies, our results highlight the need to continue studying the unusual behaviour of the actinide elements, especially those that are scarce and short-lived.

Korey P. Carter, Katherine M. Shield, Kurt F. Smith, Zachary R. Jones, Jennifer N. Wacker, Leticia Arnedo-Sanchez, Tracy M. Mattox, Liane M. Moreau, Karah E. Knope, Stosh A. Kozimor, Corwin H. Booth, Rebecca J. Abergel. "Structural and spectroscopic characterization of an einsteinium complex." 590 (7844) Nature 85 (2021). DOI: 10.1038/s41586-020-03179-3

Iberian Bell Beaker Artifacts And Other Out Of Place Artifacts In Poland

Bell Beaker blogger reports on the discovery of distinctively Iberian Bell Beaker artifacts, including distinctively Southwest Iberian style objects and a fragmented West Iberian Chalcolithic slate plaque. A naive anthropologist seeing the artifacts without being told their context would have assumed that they originated somewhere to the Southwest of Madrid, although a more careful analysis of all of the artifacts would have resulted in confusion. 

The find is remarkable, because these artifacts were found not in Iberia, but in a cremation style grave in Suprasl in northeast Poland, dated to 5,110 ± 35 cal years BP (95.4% confidence interval 3,976–3,799 cal BCE). At the time of this grave, the region was not even a part of a peripheral area where there was previous evidence of influences from an actual Bell Beaker cultural area.

This newly discovered Copper Age archaeological site in Northeast Poland has a mix of local, innovative and remote artifact styles that are out of place of this time and place which was then inhabited by European hunter-gatherers. Its location, which while inland has access to a river network to the sea, and the eclectic mix of artifacts and practices found there, along with innovations found nowhere else, suggests that its founders had roots in the heartland of the Atlantic Maritime Bell Beaker culture. This site was probably one of the farthest frontier outposts of a far flung Bell Beaker trading network that was predominantly maritime in character, but also had connections to some terrestrial trade routes in different parts of Europe, both local and distant from this outpost.

1. Location of Suprasl archaeological site (yellow star); 2 physicogeographical border of the West and East of Europe; 3 range of the Neman Cultural Circle; 4 range of the Bell Beaker phenomenon (4a culture, 4b peripheries).

The prevailing archaeological culture in the region at the time was a European hunter-gatherer culture called the Neman cultural circle, in a place where repeated efforts to transition to farming and herding didn't take, and while herding replaced hunting and gathering there soon enough (with the last hunter-gatherers gone by 1000 CE), farming wasn't well established there until the 20th century of the common era. This late adoption of food production modes involving domesticated plants and animals was presumably because the local climate was ill adapted to a package of domesticated plants and animals developed original in the Fertile Crescent of the Middle East. 

The Neman Cultural Circle cultural background of the region is described by the authors as follows in the body text of the paper that Bell Beaker blogger reviews:

The area of modern north-eastern Poland, which consists of the Masurian Lake District and the North Podlachian Lowland, was still dominated by hunter-gatherer societies of the Neman Cultural Circle (NCC) in the Late Neolithic and Early Bronze Age. In the Early Bronze Age they became apart of the Trzciniec cultural circle, which formed at that time. It is difficult to find a reason why these groups changed their cultural profile. The recurrent attempts to populate this region in the Neolithic, made by farming and pastoral communities, did not bring substantial changes in the traditional economic and social structure of the autochthonic populations which would be visible in archaeological material. Archaeological discoveries from the Masurian Lake District were the first to shed some light on the transformation of these local groups into Early Bronze Age societies. 

However, the absence of evidence necessary for conclusive identification of ‘West European immigrants’ in north-eastern Poland was a major cognitive dissonance. This big area delivered only isolated small fragments of vessels with zone-metopic decoration, which were identified with the influence of the Iwno culture (IC)– a group with a marked BB component. 

The situation changed only when features with artefacts characteristic of BB were discovered at site 3 in Supraśl in north Podlachia. The artefacts from that site can be regarded as critical for discussion of BB in northeastern Poland. It is even more interesting that up to that moment the frontier of the northeastern ecumene of this cultural phenomenon was marked by discoveries from areas previously populated by agricultural societies. 

This makes the find remarkable and paradigm modifying because the diffusion of Bell Beaker style cultural artifacts is usually assumed to have involved serial cultural transmission infused with local influences at each step, causing Bell Beaker artifacts from the epicenter of the phenomena in Southwest Iberia to become more and more different from those at the source with overland distance, particularly because if these fragile ceramic objects were actually made in Iberia and then transported by sea, they would still have had to have been transported by land and river over a substantial distance inland to the most eastern area where Bell Beaker artifacts have ever been discovered. 

As the authors explain in the body text of their new paper: 

The eco- and artefacts from these assemblages are difficult to interpret conclusively in the context of the classical BB package, and in terms of its transformations in the course of the journey ‘from neighbour to neighbour’. For this reason, the most important research issue is to establish the origin of the unearthed sources and the associated socio-cultural activity. This will also answer the question as to whether this is a case of diffusion of ideas or migration of individuals.

The mix of artifacts was eclectic, however (quoted from the body text of the cited paper):

One of the most interesting specimens in this group is a fragment of a decorated bowl with an incised zone-metopic pattern of the saltire motif, which originated in the area east of the Rhine River and is usually associated with the Veluve type. 

Another interesting item is a fragment of a profiled bowl witha wide mouth, decorated with an incised criss-cross pattern on the rim, below which a zone-metopic decoration was made with the same technique. Two decoration zones were made on the outer surface – horizontal cord impressions in the upper part, with a band of incised criss-cross pattern below. Due to its form and style, the bowl has parallels in the south-western BB zone, where the cord motifs are found together with motifs incised or impressed with a comb. Cord decoration was made in the upper portion of the vessels, sometimes on the inner surface just below the rim, and the pottery was characterized by a red-brown or reddish colour, which fully corresponds with the specimen in question. However, cord impressions are regarded as foreign in Western Europeand associated with the influence of the Corded Ware culture (CWC) (from another perspective, as one of the results of the Rückstromm). Whole it is the only specimen of pottery decorated in this manner which has been found in Podlachia, a few vessels decorated in a similar way have been discovered in north-eastern Poland – in the Masurian Lake District, where CWC and BB materials have also been unearthed. Therefore, it is possible that the vessel from Supraśl was made in the area of the Masurian Lake District.

The arrowheads at the site are typical of those found at Bell Beaker sites in the Czech Republic, central Poland, and southwestern Norway, rather than the style found in Atlantic Bell Beaker sites or the style common in Central Europe. 

The arrow shaft straighteners found at the site are of a type typical of local Mesolithic hunter-gatherers that have never been found in a Bell Beaker context before. 

The stone knives found at the site were an innovation that has no close parallels in any known prehistoric context and are made from stone probably imported from Scandinavia. 

The flint objects were not made from local materials and are typical of those found in southeastern coastal Baltic areas and southeastern French settlements and only two other examples of flint objects of this type have been found in Poland, some at the nearby Ząbie site in the Masurian Lake District, where pottery bearing BB features was also unearthed and single specimen was discovered at Święcice in Lesser Poland.

The mix of amber, stone and bone jewelry also shows diverse origins:

Cylindrical amber beads are known from BB contexts, but their territorial range is basically limited to the British Isles. The nodular bead is a form which can be found in BB burials in the Czech Republic. As opposed to the beads, the pendant was made of a natural chunk of amber and was only minimally processed to alter its shape and drill a hole in it. Parallel pendants are not known from BB contexts, but are associated with local societies from the Late Neolithic and Early Bronze Age occupying the Vistula and Oder Rivers basins. 

The processing marks visible on the surfaces under microscope as well as comparative and experimental research indicate that metal tools (a drill and a‘knife’), made of copper or copper alloy, were used in the production process. Since no traces of the use of such tools from the Late Neolithic and Early Bronze Age have been found at amber processing ‘workshops’ on Baltic coasts, it should be assumed that these artefacts originated in other areas of production. Available data suggest that in this period corresponding ‘jeweller’s’ tools were used in the British Isles and the area of the Aegean Sea. Considering other arguments, connected with the context of the analysed amber artefacts, their origin might be found in ‘jeweller’ traditions of the British Isles. Nevertheless, it does not mean that they were made there as they might as well be the products of a incomer. 

These artefacts include two pendants made of different raw materials. One of them is a mudstone pebble turned into jewellery by drilling a perforation in it. The other is a broken oval plaquette-like form made of slate and has surfaces covered with decoration, whose motifs correspond with the ones found on pottery. It shows a surprising similarity to geometric plaquettes from the south-western part of the Iberian Peninsula, dated to 3500–2750 cal BC. Some researchers regard them as representations of the Mother Goddess. Others believe these plaquettes express ‘collective heraldry’ understood as lineage identifiers, which were used as an ordered and important system for transmission of information. The latter group also emphasizes their significance in funerary rituals. However, a phylogenetic analysis recently conducted by Daniel García Riveroand Michael J. O’Brien showed that such plaquettes cannot be genealogical systems for recording generations. They also concluded that these artefacts might have had a common origin in terms of concepts, e.g., religious or apotropaic ones, and their variety was connected with different developments from the initial idea, which resulted in many variable elements, that is, mutations and variants. 

These include two objects made of different types of sandstone, two fragments of white rock: calcareous sinter and limestone rock, as well as some badly burned and fragmented human and animal bones. One of the artefacts is a small flat slab with an incised saltire and a plano-convex form made of a pebble with an incised three-arm cross on the convex surface. Neither of these objects have parallels in BB contexts. However, they are similar to pottery tokens from the Near East, used from the 8th to the 3rd millennium BC as symbolic counting aids for particular goods or their measures, e.g., for a sheep or large measure of grain.

The overall context of the find as a whole also adds more to the overall eclectic impression it leaves (although I seem to recall Bell Beaker blogger and/or the Old European Culture blog discussing the intentional destruction of artifacts in funerary-like contexts, sometimes without bodies at all, in the British Isles, possibly as a means of making a sort of divinely sanctioned oath or promise, so the authors awareness of the literature here may be limited):

[T]he origin of the ritual involving the deposition of fragments of objects, confirmed in all the features, and its incorporation into ritual practices cannot be accounted for. This practice was applied mainly in the case of pottery and some pieces of amber jewellery, or, rather rarely, weapons. Similar acts of intentional fragmentation of artefacts (mostly pottery) deposited in burials, pits and treasure contexts are known from the Neolithic and Chalcolithic discoveries in the Balkan Peninsula.

The abstract of the new paper and its citation are as follows:

The Bell Beaker (BB) cultural package is one of the concepts explaining the extensive diffusion of this phenomenon in Europe. Artefacts associated with the package, discovered mainly in the graves of men, form groups defining the status of the deceased. The BB package is a dynamic turn of events, changing depending on the region, but preserving certain characteristic traits. The complete set of its initial ingredients was not copied in any location, and new local elements wereadded in various areas of its diffusion. The ritual features unearthed in north-eastern Poland, which contained elements of the BB package, are the assemblages located the furthest in the East European periphery of the phenomenon. The eco- and artefacts from these assemblages are difficult to interpret conclusively within the framework of the classic BB package, as well as in terms of its changes associated with its diffusion. This is connected with the fact that they include elements unknown among the local cultural entities, which reflect the broad circle of contacts their owners maintained.

Manasterski et al., "Bell Beaker cultural package in the Eastern European periphery of the phenomenon: a case of ritual features in north-eastern Poland", Documenta Praehistorica XLVII (2020).

The authors attempt to cobble together a narrative of a long single journal that might explain this odd and out of place mix of materials in their discussion section, but I omit it, as it only barely hangs together and close this post with their conclusions, beginning with a description of the physical geographic context of the site which resembles an English moor with associated bogs:

Supraśl site 3 is an isolated sandy elevation situated among water-logged meadows associated with wetlands of the Supraśl River, which is now a regulated watercourse. They occupy a stretch of land which is more than a kilometre wide. The landscape in its vicinity consists of barren moraine hills covered with forests as well as lakes and ponds, mostly with peat vegetation. Palynological analysis shows that these areas were only sporadically used for farming from the Early Bronze Age to the 20th century AD. At the same time, they were a perfect location for the economic activity of hunter-gatherer societies, which were represented by NCC in the late 3rd and early 2nd millennium BC. For this reason, it could be surprising that BB representatives arrived in this region.

The answer can be found in the analysis of the natural and archaeological context. On one hand, there existed a water communication network which served for transport and isolated artefacts with typical BB components were found. On the other hand, it was close to chalk flint mines located along the Ros River and flint workshops situated in the vicinity of the mines. 

All these indicate that this was most likely an attempt to find trade partners and organize communication routes or take control of the existing ones. For these reasons, it should not be surprising that mainly isolated BB artefacts without a clear settlement or funerary context were unearthed in north-eastern Poland. 

The discoveries from Supraśl 3 escape this pattern. They cannot be conclusively classified as isolated finds, settlement relics, or classic burials. 

Both the choice of the place (an isolated ‘island’ among wetlands, with access from the river-side, surrounded by large forests – a secret place for the initiated) and the selection of the objects in the discovered features suggest that relics of a certain form of a ritual system, most probably funerary practices, were found. This is indicated by the presence of human cremation remains identified in two features as well as sets of artefacts found in burials of BB men – archers/warriors (beakers, archer’s accessories, daggers, jewellery). The recurrence of the sets of eco- and artefacts and their arrangement in the assemblages suggest the existence of ritual traditions. 

Although most pottery vessels and the decorated slate plaquette/pendant may suggest their Iberian lineage, it is difficult to list parallels in terms of place and behaviour relics. This is relevant to both autochthonic and allochthonic societies occupying north-eastern Poland.

This site seems analogous to the the Bent's Old Fort National Historic Site in rural Southeastern Colorado that was operational from 1833 CE to 1849 CE, and which, for much of its 16-year history, was the only major white American permanent settlement on the Santa Fe Trail between Missouri and the Mexican settlements close to the Arkansas River.

Bent's Fort was an early, long term frontier trading post and military destination of a geographically remote, comparatively technologically advanced culture to the local one, trading (and intermarrying, in the case of Bent's Fort, it is hard to tell at this northeast Polish site) not just with the local populations (at least two linguistically distinct Native American tribe in the region), but also with different but with members of other comparably technologically advanced cultures (mostly Mexican and French) exploring and trading in this frontier region at the same time, as part of a very far flung trade network, resulting an eclectic mix of goods and practices that were highly atypical of the general region.

Harappan, Dravidian and Indo-Aryan Legacies

Razib Khan has made some interesting posts at Brown Pundits and at his other online forums in early 2021, one of which I agree with completely, and another of which I think is probably not on target. I started writing this responsive post at the time, but go derailed. I've completed it and posted it now with only modest revision.

In the post that I fully agree with, regarding the Y-DNA of Brahmins in India, he writes at Brown Pundits (some linked added by me):

I was talking to a person of South Indian Brahmin origin today about their genetics. Over the course of the conversation, he showed me Y and mtDNA haplogroup types amongst his jati. The vast majority of the Y haplogroups were not R1a.

Brahmin groups in India seem to be about 15% to 30% steppe in their overall genome. But their Y chromosomes are usually 50% or so R1a1a-Z93. The lineage associated with Indo-Iranian pastoralists.

So what’s going on with the other haplogroups? For example, J2, L, C, G, and H?

From what I can see J2 and L are the next most frequent haplogroups after R1a1a-Z93. This tells us something. These are haplogroups found in ancient “Indus Periphery” samples. And, these two haplogroups are found at high concentrations in the northwest of the subcontinent.

It doesn’t take a Brahmin to connect the dots here. Some of the gotra as early as the Vedic period were almost certainly derived from high-status individuals in the post-IVC society. Warriors and priests in the fallen civilization of the IVC, which had likely degraded itself to a level of barbarism by the time the Indo-Aryans became ascendant.

The notion that the mostly Indo-Aryan steppe people who were a leading component of the Brahmin class also included elites from the Harappan culture which was already in some stage of collapse when they migrated to South Asia seems very likely.

Relevant Y-DNA Haplogroups

Y-DNA H is the most definitively autochthonous Y-DNA haplogroup of India and South Asia, is most common in Sri Lanka (25%), South India (26-27%) and Bangladesh (36%), fairly common in North India (25% but varying from 10% to 44% by caste with lower frequencies in high caste and higher frequencies in low caste) and Nepal (6%-39% with large regional variation and the high frequencies restricted to villages with founder effect issues). 

Y-DNA H frequencies are much lower in even nearby adjacent populations Pakistani populations have 3-8% (except the genetically distinctive the Kalash with 20%) and Afghanistan has 6-7%. But it is found in 30%-60% of men in most Roma populations of Europe (a.k.a. Gypsy, with all collective names for this people being somewhat problematic) which are derived from India.

Y-DNA L has a South Asian centered distribution but a quite different distribution than Y-DNA L, suggestive of West Asia origins. It has higher frequency among members of Dravidian castes (ca. 17-19%) (as opposed to sub-caste Dalit and "tribal" people of India) but is somewhat rarer in members of Indo-Aryan castes (ca. 5-6%). It is also present at high frequencies among the Kalash.

Y-DNA J2 and G have a distribution suggestive of West Asian origins.

Haplogroup J2 has been present in South Asia mostly as J2a-M410 and J2b-M102, since neolithic times (9500 YBP). J2-M172 was found to be significantly higher among Dravidian castes at 19% than among Indo-European castes at 11%. J2-M172 and J-M410 is found 21% among Dravidian middle castes, followed by upper castes, 18.6%, and lower castes 14%. . . . 

In Pakistan, the highest frequencies of J2-M172 were observed among the Parsis at 38.89%, the Dravidian speaking Brahui's at 28.18% and the Makrani Balochs at 24%. It also occurs at 18.18% in Makrani Siddis and at 3% in Karnataka Siddis. J2-M172 is found at an overall frequency of 16.1% in the people of Sri Lanka.

What role did Harappans play in Dravidian ethnogenesis?

I am much more skeptical of Razib Khan's conjecture in another post at Brown Pundits. He writes:

Peter Bellwood in First Farmers presents a hypothesis for the expansion of the Dravidian languages into southern India in the late Neolithic through the spread of an agro-pastoralist lifestyle through the western Deccan, pushing southward along the Arabian sea fringe. At the time I was skeptical, but now I am modestly confident that this is close to the reality. 

[The South Indian Neolithic was probably the source of the expansion of the Dravidian languages, from a focal point in southern India, not "into it", and given that it involved a mix of Sahel African domesticates, Fertile Crescent Neolithic domesticates, and a few local domesticates, I suspect that there were maritime impact from Africa, and as well as borrowings from IVC agriculturists. But the IVC culture didn't spread south sooner because the Fertile Crescent package of crops didn't thrive well enough to support a Neolithic culture by itself in southern India so the input of Sahel African domesticates was probably the critical final piece of the puzzle.]

There is always talk about “steppe” ancestry on this weblog. But there are groups that seem “enriched” from IVC ancestry, as judged by the Indus Periphery samples. The confidence is lower since we don’t have nearly as good a sample coverage…but I think I can pass on what we’ve seen so far: groups in southern Pakistan, non-Brahmin elites in South India, and some Sudra groups in Gujarat and Maharashtra, seem to be relatively enriched for IVC-like ancestry. Then there is the supposed existence of Dravidian toponyms in Sindh, Gujarat, and Maharashtra. And, their total absence in the Gangetic plain.

[Discussed below.] 

There have been decades of debate about Brahui. I’ve looked closely at Brahui genetics, and they are no different from the Baloch. Combined with evidence from Y chromosomes (the Baloch and Brahui have some of the highest frequencies of haplogroups found in IVC-related ancient DNA), I doubt the thesis they are medieval intruders (if they are, their distinctive genes were totally replaced).

[The case that they are medieval intruders whose distinctive genes were totally replaced is the stronger one as discussed below.] 

Genetically, we know that some southern tribes, such as the Pulliyar, have some IVC-related ancestry. But other groups, such as Reddy in Andhra Pradesh, have a lot more. How does this cline emerge? 

[Discussed below.] 

My conjecture is that there were several movements of “Dravidian” people from Sindh and Gujarat into southern India, simultaneous with the expansion of Vedic Aryans to the north into the Gangetic plain. The region the Vedic Aryans intruded upon, Punjab, was not inhabited by Dravidian speakers. Like Mesopotamia, the Indus Valley Civilization was probably multi-lingual, despite broad cultural affinities developed over time.

[I disagree with almost all of this as discussed below.] 

I don't disagree that he is correct on the distribution of Dravidian toponyms or the enhanced levels of IVC-type genetics where he notes it. But I do disagree with the narrative he provides for those facts.

The strongest evidence for a ca. 1000 CE origin for the Brahui, rather than a deep and ancient one, is linguistic. The Brahui language contains linguistic innovations not present in the Dravidian languages until after about 1000 CE that are specific to the North Dravidian language of which it is one.

All of the communities with North Dravidian language speakers also have traditions of an origin in the Deccan Peninsula, which are more likely to have persisted over time in a more recent migration.

Brahui is spoken beyond and outside the range of widespread Dravidian toponyms, which once established tend to be stable.

Obviously, the genetics suggests a scenario of elite language shift with only a little, possibly no longer discernible due to dilution, demic contribution to the population genetics of the founding elite. But, this is not unprecedented. Something similar took place in Hungary in about the same era. In Turkey, also in roughly the same era, there was language shift with a quite modest ethnically Turk genetic contribution, and more than twenty centuries before that, language shift to the Hittite language was also elite dominated. In South Asia, there was more demic impact, but the language shift to Sanskrit derived Indo-Aryan languages was still elite dominated. This also happened in post-Columbian Latin America.

In the Indus River Valley itself and adjacent areas, IVC ancestry is likely due to Harappan migration (a society that was not Dravidian language speaking although it had contacts with Dravidian language speakers) prior to the arrival of the Indo-Aryans, and this is probably the source of IVC ancestry in the Brahui.

The archaeological evidence and ancient seals and limits historical accounts from Mesopotamia, all tend to disfavor the conclusion that the "Indus Valley Civilization was probably multi-lingual", and instead tend to favor a linguistic, cultural, and political unity maintains from the outset of its adoption of Fertile Crescent agriculture that persisted until close to its collapse. There isn't evidence of war or war-like fortifications in the core IVC region until very late, which political unity which usually leads to linguistic and cultural unity, can produce.

There is also essentially no evidence for the narrative that "there were several movements of “Dravidian” people from Sindh and Gujarat into southern India, simultaneous with the expansion of Vedic Aryans to the north into the Gangetic plain." 

The evidence instead suggests that the migrations went the other way and ultimately collapsed in some areas, leaving only toponyms and a few isolated linguistic communities like the Brahui and other Northern Dravidian enclaves from a high water mark of Dravidian expansion from South India.

Moorjani, et al., "Genetic Evidence for Recent Population Mixture in In India" 93 American Journal of Human Genetics 422-438 (September 5, 2013) estimated the admixture history of India based upon an analysis of a moderate sized samples of modern Indian genomes. 

Moorjani found that the timing of admixture was later than the South Asian Neolithic era and was in some cases consistent with only a single wave of admixture based not only on Linkage Disequilibrium methods (which are less prone to uncertainty that mutation rate methods) but also by confirming that the components that did admix were consistent with being from the same autosomal gene pools as opposed to different ones as would be expected if there were two waves of admixture from different sources. 

Ancestral North Indian (ANI) ancestry is a mix of steppe ancestry and ancestry from co-opted IVC people. The admixture into Dravidian peoples is older, reflecting a broad sweep of the subcontinent that went unchecked, but presumably was then beaten back in a Dravidian reconquest of Southern India, which accounts for both the fact that these regions don't speak Indo-Aryan languages now (although the pro-Hindu religion stuck), and the deceptively young apparent age of the Dravidian language family due to the extinction of all Dravidian dialects except the relict core from which the reconquest was mounted. In contrast, in linguistically Indo-Aryan North India, there was a second pulse of steppe introgression that came later. 

The higher ratio of IVC genetics to steppe ancestry in South Indian Brahmins likely reflects a narrative in which lower status post-IVC local elites sought positions leading the conquest of South India at a greater rate than higher status steppe elites, because they had better opportunities for promotion there, and may also, more conjecturally, found the climate less out of their comfort zone than the steppe elites who were already at the fringe of their comfort zones in North India. 

The abstract and body text of Moorjani (2013) notes that:

Genetic evidence indicates that most of the ethno-linguistic groups in India descend from a mixture of two divergent ancestral populations: Ancestral North Indians (ANI) related to West Eurasians (people of Central Asia, the Middle East, the Caucasus, and Europe) and Ancestral South Indians (ASI) related (distantly) to indigenous Andaman Islanders. The evidence for mixture was initially documented based on analysis of Y chromosomes and mitochondrial DNA and then confirmed and extended through whole-genome studies.

Archaeological and linguistic studies provide support for the genetic findings of a mixture of at least two very distinct populations in the history of the Indian subcontinent. The earliest archaeological evidence for agriculture in the region dates to 8,000–9,000 years before present (BP) (Mehrgarh in present-day Pakistan) and involved wheat and barley derived from crops originally domesticated in West Asia. The earliest evidence for agriculture in the south dates to much later, around 4,600 years BP, and has no clear affinities to West Eurasian agriculture (it was dominated by native pulses such as mungbean and horsegram, as well as indigenous millets). 

Linguistic analyses also support a history of contacts between divergent populations in India, including at least one with West Eurasian affinities. Indo-European languages including Sanskrit and Hindi (primarily spoken in northern India) are part of a larger language family that includes the great majority of European languages. In contrast, Dravidian languages including Tamil and Telugu (primarily spoken in southern India) are not closely related to languages outside of South Asia. Evidence for long-term contact between speakers of these two language groups in India is evident from the fact that there are Dravidian loan words (borrowed vocabulary) in the earliest Hindu text (the Rig Veda, written in archaic Sanskrit) that are not found in Indo-European languages outside the Indian subcontinent.

Although genetic studies and other lines of evidence are consistent in pointing to mixture of distinct groups in Indian history, the dates are unknown. Three different hypotheses (which are not mutually exclusive) seem most plausible for migrations that could have brought together people of ANI and ASI ancestry in India. The first hypothesis is that the current geographic distribution of people with West Eurasian genetic affinities is due to migrations that occurred prior to the development of agriculture. Evidence for this comes from mitochondrial DNA studies, which have shown that the mitochondrial haplogroups (hg U2, U7, and W) that are most closely shared between Indians and West Eurasians diverged about 30,000–40,000 years BP. The second is that Western Asian peoples migrated to India along with the spread of agriculture; such mass movements are plausible because they are known to have occurred in Europe as has been directly documented by ancient DNA. Any such agriculture related migrations would probably have begun at least 8,000–9,000 years BP (based on the dates for Mehrgarh) and may have continued into the period of the Indus civilization that began around 4,600 years BP and depended upon West Asian crops. The third possibility is that West Eurasian genetic affinities in India owe their origins to migrations from Western or Central Asia from 3,000 to 4,000 years BP, a time during which it is likely that Indo-European languages began to be spoken in the subcontinent. A difficulty with this theory, however, is that by this time India was a densely populated region with widespread agriculture, so the number of migrants of West Eurasian ancestry must have been extraordinarily large to explain the fact that today about half the ancestry in India derives from the ANI. It is also important to recognize that a date of mixture is very different from the date of a migration; in particular, mixture always postdates migration. Nevertheless, a genetic date for the mixture would place a minimum on the date of migration and identify periods of important demographic change in India. . . . 

Most Indian groups descend from a mixture of two genetically divergent populations: Ancestral North Indians (ANI) related to Central Asians, Middle Easterners, Caucasians, and Europeans; and Ancestral South Indians (ASI) not closely related to groups outside the subcontinent. The date of mixture is unknown but has implications for understanding Indian history. We report genome-wide data from 73 groups from the Indian subcontinent and analyze linkage disequilibrium to estimate ANI-ASI mixture dates ranging from about 1,900 to 4,200 years ago. In a subset of groups, 100% of the mixture is consistent with having occurred during this period. . . . 

By using f4 ratio estimation that analyzes allele frequency correlation patterns to infer mixture proportions, we estimate that ANI ancestry along the Indian cline ranges from as low as 17% (Paniya) to as high as 71% (Pathan). Traditionally lower caste, Dravidian, and tribal groups tend to have lower proportions of ANI ancestry than traditionally upper caste and Indo-European groups (p < 0.001). . . . 

To date ANI-ASI mixture, we capitalized on the fact that admixture between two populations generates allelic association (linkage disequilibrium [LD]) between pairs of SNPs. The LD decays at a constant rate as recombination breaks down the contiguous chromosomal blocks inherited from the ancestral mixing populations. The expected value of the admixture LD is related to the genetic distance between SNPs (the probability of recombination per generation between them) and the time that has elapsed since mixture. We previously reported simulations showing that dating population mixture based on the scale of admixture LD is robust to the use of imperfect surrogates for the ancestral populations, fine-scale errors in the genetic map, and a history of founder events in the admixed population, and is able to provide unbiased estimates for the dates of events up to 500 generations ago. We confirmed this by using new simulations with demographic parameters relevant to India. 

We estimated admixture dates for all the groups on the Indian cline with more than five samples (a minimum sample size is important for measuring LD with precision). We observe a decay of LD with genetic distance for all groups. By fitting an exponential function using least-squares (via rolloff), our point estimates for the dates range from 64 to 144 generations ago, or 1,856 to 4,176 years assuming 29 years per generation.

We highlight two implications of these dates. 

First, nearly all groups experienced major mixture in the last few thousand years, including tribal groups like the Bhil, Chamar, and Kallar that might be expected to be more isolated. 

Second, the date estimates are typically more recent in Indo-Europeans (average of 72 generations) compared to Dravidians (108 generations). A jackknife estimate of the difference is highly significant at 35 ± 8 generations (Z = 4.5 standard errors from zero). A possible explanation is a secondary wave of mixture in the history of many Indo-European groups, which would decrease the estimated admixture date. . . . 

A caveat for these dating analyses is that they assume that the entire admixture occurred instantaneously (or over a small number of generations). However, population mixture can be noninstantaneous, such that the date we obtain from our method may actually be an average of multiple dates spread out over a substantial period. One way to detect a history of noninstantaneous gene flow is to fit a sum of exponential functions to the decay of admixture LD and to show that this provides a better fit to the data than a single exponential function, as we in fact find for the Kashmiri Pandit, Kshatriya, Sindhi, and Pathan. However, even if we fail to detect a nonexponential decay, we cannot rule out noninstantaneous gene flow, because the decay can be noisy, making the statistical detection of a mixture of exponential functions difficult. 

A particularly important scenario we could not rule out by this method is that several thousand years ago, Indian groups were already admixed, and thus the LD decay we detect is the result of mixture of already admixed ancestral groups with different proportions of ANI ancestry. If the initial admixture was more than 10,000 years old, the associated admixture LD would have decayed to such a short distance that our methods would have poor power to detect it. The LD we measure might in this case reflect only the final admixture events, complicating interpretation of the results. . . . 

[W]e identified previously undetected complexity in Indian history, with many sets of Indian groups not consistent with a simple ANI-ASI admixture. . . . . we find that the Indian groups consistent with simple ANI-ASI mixture are most often from tribal and traditionally lower-caste groups. Middle- and upper-caste groups tend to have evidence of more complex histories, with signals of multiple layers of ANI ancestry from slightly different ANI ancestral populations. Further evidence for multiple waves of admixture in the history of many traditionally middle- and upper-caste groups (as well as Indo-European and northern groups) comes from the more recent admixture dates we observe in these groups and the fact that a sum of two exponential functions often produces a better fit to the decay of admixture LD than does a single exponential. Evidence for multiple components of West Eurasian-related ancestry in northern Indian populations has also been reported by Metspalu et al. based on clustering analysis. 

Focusing on the largest set of Indo-Europeans (four groups) and the largest set of Dravidians (five groups) consistent with mixture of the same ANI and ASI ancestral populations, we find that the expected and observed admixture LD amplitudes are equivalent to within the limits of our resolution. . . . our data are consistent with all of the ANI ancestry in some selected sets of Indians (including groups speaking both Indo-European and Dravidian languages) being due to admixture events that we can date to within the past few thousand years. Accounting for statistical uncertainty, we estimate that the ANI ancestry that cannot be explained by a single wave of admixture in the last few thousand years has a 95% confidence interval (truncated to 0) of 0%–19% for Indo-Europeans and 0%–16% for Dravidians. Thus, all the ANI ancestry in some groups is consistent with deriving from admixture events that have occurred in the past few thousand years. 

Our analysis documents major mixture between populations in India that occurred 1,900–4,200 years BP, well after the establishment of agriculture in the subcontinent. We have further shown that groups with unmixed ANI and ASI ancestry were plausibly living in India until this time. This contrasts with the situation today in which all groups in mainland India are admixed. 

These results are striking in light of the endogamy that has characterized many groups in India since the time of mixture. For example, genetic analysis suggests that the Vysya from Andhra Pradesh have experienced negligible gene flow from neighboring groups in India for an estimated 3,000 years. Thus, India experienced a demographic transformation during this time, shifting from a region where major mixture between groups was common and affected even isolated tribes such as the Palliyar and Bhil to a region in which mixture was rare. Our estimated dates of mixture correlate to geography and language, with northern groups that speak Indo-European languages having significantly younger admixture dates than southern groups that speak Dravidian languages. This shows that at least some of the history of population mixture in India is related to the spread of languages in the subcontinent. 

One possible explanation for the generally younger dates in northern Indians is that after an original mixture event of ANI and ASI that contributed to all present-day Indians, some northern groups received additional gene flow from groups with high proportions of West Eurasian ancestry, bringing down their average mixture date. This hypothesis would also explain the nonexponential decays of LD in many northern groups and their higher proportions of ANI ancestry. . . .

The dates we report have significant implications for Indian history in the sense that they document a period of demographic and cultural change in which mixture between highly differentiated populations became pervasive before it eventually became uncommon. The period of around 1,900–4,200 years BP was a time of profound change in India, characterized by the deurbanization of the Indus civilization, increasing population density in the central and downstream portions of the Gangetic system, shifts in burial practices, and the likely first appearance of Indo-European languages and Vedic religion in the subcontinent. The shift from widespread mixture to strict endogamy that we document is mirrored in ancient Indian texts. The Rig Veda, the oldest text in India, has sections that are believed to have been composed at different times. The older parts do not mention the caste system at all, and in fact suggest that there was substantial social movement across groups as reflected in the acceptance of people with non-Indo-European names as kings (or chieftains) and poets. The four-class (varna) system, comprised of Brahmanas, Ksatriyas, Vaisyas, and Sudras, is mentioned only in the part of the Rig Veda that was likely to have been composed later (book 10). The caste (jati) system of endogamous groups having specific social or occupational roles is not mentioned in the Rig Veda at all and is referred to only in texts composed centuries after the Rig Veda, for example, the law code of Manu that forbade intermarriage between castes. Thus, the evolution of Indian texts during this period provides confirmatory support as well as context for our genetic findings. 

It is also important to emphasize what our study has not shown. Although we have documented evidence for mixture in India between about 1,900 and 4,200 years BP, this does not imply migration from West Eurasia into India during this time. On the contrary, a recent study that searched for West Eurasian groups most closely related to the ANI ancestors of Indians failed to find any evidence for shared ancestry between the ANI and groups in West Eurasia within the past 12,500 years (although it is possible that with further sampling and new methods such relatedness might be detected). 

An alternative possibility that is also consistent with our data is that the ANI and ASI were both living in or near South Asia for a substantial period prior to their mixture. Such a pattern has been documented elsewhere; for example, ancient DNA studies of northern Europeans have shown that Neolithic farmers originating in Western Asia migrated to Europe about 7,500 years BP but did not mix with local hunter gatherers until thousands of years later to form the present-day populations of northern Europe. 

The most remarkable aspect of the ANI-ASI mixture is how pervasive it was, in the sense that it has left its mark on nearly every group in India. It has affected not just traditionally upper-caste groups, but also traditionally lower-caste and isolated tribal groups, all of whom are united in their history of mixture in the past few thousand years. 

The Self-Coupling of the Higgs Boson

In the Standard Model, all of the properties of the Higgs boson, except its mass, can be calculated from first principles, and the global average measurement of its rest mass is 125.10 ± 0.14 GeV, a precision of about one part per 894.

In the Standard Model, the strength of the interactions of the Higgs boson with the fundamental particles, their so called "Yukawas" is proportional to the rest mass of those particles. The Higgs field also gives mass to the Higgs boson itself in proportion to its rest mass in the Standard Model.

The strength of the coupling of the Higgs boson with itself that is observed experimentally can can compared to a benchmark Standard Model value it has at its measured value, with the value equal to exactly one if the the experimentally measured value matched the predicted one. 

If the experimentally measured value were higher, it would be proportionately more than one. If the experimentally measured value were lower, it would be proportionately less than one. It the experimentally measured value were opposite in direction to the exacted value (e.g. by analogy, if the electromagnetic force were repulsive when it was expected to be attractive) then the value is negative.

Tommaso Dorigo reports on the best measurement of the Higgs boson self-coupling to date, from was published by the CMS Collaboration at the Large Hadron Collider (LHC) back in November. Their measurement bounds the Higgs self-coupling to be between -2.7 and 8.6 (relative to a benchmark value of 1.0) within 95% confidence intervals. 

This is consistent with the Standard Model prediction, but with lots of uncertainty because it is a hard measurement to make of something that can only happen with any frequency towards the high end of the energy scales that the LHC can produce. Also, while this isn't a terribly tight constraint (many of its interactions are constrained much more tightly), it is sufficiently tight to rule out a large swath of beyond the Standard Model theories that predicted more dramatic deviations from the Standard Model prediction.

Combining the observed strength of all Higgs boson interactions observed to date, in which 1.0 is the Standard Model prediction, the experimentally observed values so far have been 1.13 ± 0.06, a slight tension with the Standard Model prediction, but still remarkably close to properties predicted theoretically in the 1960s, more than half a century ago, when scientists still used slide rules and punch card mainframe computers to do calculations.