750 GeV Resonance Gone, SM Repeatedly Confirmed, Higgs Boson Trending Lighter

Lubos Motl has a good summary of the CMS experiment's results based upon the first day of talks at the ICHEP conference in Chicago and some related papers that were released.

Jester's twitter feed provides some charts and analysis generally confirming his conclusions.  So does Matt Strassler's blog.

1. There Is No 750 GeV Bump. The big news is the highly anticipated (and widely rumored) result related to the 750 GeV diphoton bump. A prematurely released CMS paper on the 750 GeV resonance, a bump that has spawned 500 recent papers over roughly the last half year, shows that it has disappeared with the new data. How much new data? Much more than the data set that provide the initial evidence of a bump.

The relevant portion of the data taken by CMS in 2016 is usually given by 12.9 inverse femtobarns of data. Note that this whole 12.9 was taken in the first half of 2016. They never combine the 2015 and 2016 data. They could combine them and increase 12.9 by something like 2.7 that is used in many CMS papers based on the 2015 data.

UPDATE: ATLAS concurs that the 750 GeV bump is not present in the new data (full paper here). See also here.

2. Standard Model Confirmation. The overwhelming share of 39 papers dumped by CMS in connection with the conference perfectly confirm the Standard Model in all but 7 cases (with multiple hypotheses tested in each of most of the papers).  Only one result had a deviation from the Standard Model with more than 2.6 sigma of statistical significance, and that has a 2.84 sigma global significance.  This is in the ballpark for the number of anomalies of this significance that would be expected due to random statistical flukes in a dump of this many results at once.

Only a couple of the anomalies also showed up in previous data sets and at least one of those had an anomaly of declining statistical significance despite the fact that a larger data set that should increase the statistical significance of an anomaly found in prior data that was real by about 2.5 sigma over the previous data set.  So far, there is also no meaningful ATLAS confirmation of the CMS anomalies.

SUSY exclusions and other BSM exclusions exclude more parameter space than they did after the last round of data was analyzed.  Some SUSY exclusions rule out certain sparticals (gluinos) under certain assumptions up to 1.9 TeV.

3. Higgs Boson Mass.  The latest measurement of the Higgs boson mass (based upon four lepton events) by CMS was 124.5 +0.48/-0.46 GeV. This is less than the current global average of about 125.09 +/- 0.24 GeV, which is statistically consistent with the global average but will probably drag down a new global average somewhat, although there is a considerable range of data points that contribute to that global average.

What does the new CMS Higgs boson measurement mean in context?

The current combined estimate of the Higgs boson mass (from the link to that value above) is based upon the following data points:

* ATLAS diphoton mass 126.02 +/- 0.51 GeV
* ATLAS four lepton mass 124.51 +/- 0.52 GeV
* CMS diphoton mass 124.7 +/- 0.34 GeV
* CMS four lepton mass 125.59 +/- 0.45 GeV

So, after this new CMS data point, the new global average should be roughly 124.82 GeV with a pretty similar margin of error, before accounting for any new ATLAS results with its wealth of new data.

The new CMS data point also makes the ATLAS diphoton data point look like an outlier relative to the other three measurements, which suggests that we may expect the combined average is more likely to fall than to rise when ATLAS releases its next Higgs boson diphoton decay based mass measurement, bringing the combined average closer to the theoretically notable value of 124.65 GeV discussed below.

Some of the prior Higgs boson mass measurements at the LHC (by date of publication, some of which were used in the current combined average) include the following:

* ATLAS diphoton mass 125.98 +/- 0.42 +/- 0.28 (June 15, 2014)
* ATLAS four lepton mass 124.51 +0.52 +/- 0.06 (June 15, 2014)
* CMS diphoton number 124.7 +/- 0.31 +/- 0.15 (July 2, 2014)
* CMS four lepton mass 125.6 +/- 0.4 +/- 0.2 (September 10, 2014)

The new CMS four lepton mass measurement is very close to the June 15, 2014 ATLAS four lepton mass measurement.

The downward trend in the Higgs boson mass revives the possibility that the sum of the squares of the fundamental boson masses is equal to half of the square of the Higgs vacuum expectation value (VEV).  The Higgs boson mass in that scenario would be 124.65 GeV (which is robust to variations within the current margin of error of the W and Z boson masses).  This is consistent within two sigma of the current global average, within one sigma of the latest CMS four lepton based measurement of the Higgs boson mass, and even closer to the likely combined global average once the new CMS result is considered.

It also further disfavors the 2W+Z=2H mass formula, which is already disfavored by 3.7 sigma with the current global average, to the point that it is pretty much conclusively ruled out.

As previously noted at this blog:

There is an argument that the "tree-level" mass of the Higgs boson is 123.114 GeV (half the Higgs vev) but that it is increased by higher order loop corrections that bring it to its experimental value. The "tree-level" estimate of the mass of the W boson is 78.9 GeV. If the percentage increase in mass due to higher order loop corrections for the Higgs boson from the tree level value is the same as the higher order loop corrections of the W boson to the experimental value, then the implied Higgs boson mass value would be 125.43 GeV which is consistent at a 1.4 sigma level with the latest combined mass measurement. No published source actually calculates these higher order loop adjustments, however. While the actual higher order loop calculation is probably of that order of magnitude, it could easily be higher or lower. The claim is plausible, but requires further investigation. If the higher order loop corrections produced a value consistent with 124.65 GeV, that would be remarkable indeed[.] . . . 

This also significantly tightens the expected value of the top mass from the formula that the sum of the square of each of the fundamental particle masses equals the square of the Higgs vacuum expectation value. The uncertainty in the Higgs boson mass had been the second greatest source of uncertainty in that calculation. The best fit for the top quark mass on that basis (using a global fit value of 80.376 GeV for the W boson rather than the PDG value) is 173.73 GeV (173.39 to 174.07 GeV within the plus or minus one sigma band of the current Higgs boson measurement). 

If the the sum of the square of the boson masses equals the sum of the square of the fermion masses the implied top quark mass is 174.03 GeV if pole masses of the quarks are used, and 174.05 GeV if MS masses at typical scales are used.

That compares to the latest top quark mass estimate from ATLAS of 172.99 +/- 0.91 GeV. The latest combined mass estimate of the top quark (excluding the latest top quark mass measurement estimate from ATLAS) is 173.34 +/- 0.76 GeV.

The expected value of the top mass from the formula that the sum of the square of each of the fundamental particle masses equals the square of the Higgs vacuum expectation value, goes up if the Higgs boson mass is reduced.

Other Higgs boson news:

In general, there have been a long string of Higgs boson reports from the LHC tending to show a very tight correspondence between all of the experimentally measured properties of the Higgs boson and the theoretically predicted properties of a Higgs boson of roughly the measured Higgs boson mass. The latest measurements of Higgs boson properties announced today are no exception to this trend.

Strong (3.3 sigma) but not discovery level evidence is found at ATLAS for a Higgs process involving top quark pairs in the frequencies consistent with those predicted by the Standard Model.

Previous experiments have also confirmed that the Higgs boson is spin-0, even parity, and has couplings of the predicted strength all of the now nearly half dozen couplings that have been measured.

Back To Basics About Supersymmetry

The following questions and answers are copied from questions posted and answers I wrote at the Physics Forum (with some significant editing, expanded text, and reformating):

Questions:

What is the point of sparticles? What will they prove? How will they work? I've read about supersymmetry, but don't really get it. I know it is to unify quantum mechanics and relativity, but how?

Answer:

Sparticles are particles beyond the Standard Model of particle physics that are necessary for supersymmetry which is a generalization of the Standard Model of particle physics that is attractive for reasons of interest to theoretical physicists.

Standard Model Fundamental Fermions and Bosons

In the Standard Model of particle physics, there are two basic kinds of particles.

In the Standard Model, fundamental fermions are the building blocks of what we crudely in layman's language think about as "matter".  For example, a hydrogen atom is made of three quarks that combine to form a proton with an electron orbiting around it. The six kinds of quarks are fundamental fermions, and these fundamental fermions combine to make protons, neutrons and more exotic composite particles called hadrons which are made of two (mesons) or three (baryons) or more quarks.  Particles made up of quarks are often accompanied by orbiting electrons, or muons (heavy electrons), or taus (really heavy electrons).  When muons and taus and other fundamental particles decay into lighter particles they spew out one of three kinds of neutrinos (which are very light, but non-zero mass particles that interact barely at all except via the weak force and gravity).  Electrons, muons, taus and the three kinds of neutrinos combined are fundamental fermions that are similar in certain ways and are collectively called leptons. 

In the Standard Model, fundamental bosons are we crudely think of in layman's language as the particles that make up force fields.  Electromagnetic fields are made of bosons called photons. Protons and neutrons and other particles made of quarks (which are fundamental fermions) that are held together by bosons called gluons which carry the strong force.  The weak force is carried by bosons called the W boson (for "weak") and the Z boson (because they needed to give it a name and didn't have any other good ones). Gravity, if it is a field carried by a particle is carried by a hypothetical boson called a graviton.  The Higgs boson carries the "Higgs field" which gives fundamental particles their mass (it isn't clear whether or not the Higgs boson interacts with neutrinos which may get their mass in a different way, how neutrinos get their mass is an unsolved problem in physics).

Supersymmetry Is A Balance Between Fundamental Fermions and Fundamental Bosons

Without getting into all the technical details, supersymmetry (also known as SUSY) is basically about the idea that there are technical reasons that makes it desirable for there to be a fundamental balance between fundamental fermions and fundamental bosons.

The theoretically easiest way to get that balance is to imagine that every fundamental fermion has a new fundamental particle boson counterpart (squarks and sleptons), and that every fundamental boson has a new fundamental fermion counterpart, which have their own special names.* These partner particles are "sparticles."

This then gets jumbled a bit because some of these counterparts have very similar physical properties that cause them to blend into each other and look like different particles (something that happens in the Standard Model as well in the way that the electromagnetic force and weak force are related to each other in very deep ways call electroweak unification), and the theory also requires at least four extra Higgs bosons to work out (a positively charged one, a negatively charged one, an extra heavy one, and one with a different parity - i.e. left handedness v. right handedness than a usual Higgs boson).

More complicated "non-minimal" versions of supersymmetry assume even more new particles.

* It could be that a balance between fundamental fermions and fundamental bosons already exists in the Standard Model in a much more subtle way than the crude and obvious balancing present in supersymmetry theories, which would explain how seemingly "unnatural" aspects of the Standard Model "miraculously" balance out, but so far only the vaguest hints that this might be the case have been worked out by theoretical physicists and only as conjectures and hypotheses, not as proven theories.

Supersymmetry is a GUT and SUGRA is a TOE.

Supersymmetry itself does not unify quantum mechanics and relativity. Instead, it unifies the three forces of the Standard Model (electromagnetism, strong force, weak force) into forms of the same underlying force that is unified at high energies, making it what is known as a Grand Unified Theory (GUT). Supersymmetry also ties in naturally to some mathematical structures known as "groups" in a more elegant way than the Standard Model does (which takes at least three different groups crudely "glued" together to summarize).

If you add quantum gravity to the supersymmetry mix by adding the graviton (a fundamental boson) and a superpartner called a gravitino (a fundamental fermion), you get supergravity also known as SUGRA which is a low energy approximation of a Theory of Everything (TOE), and supergravity, in turn is usually a foundation of string theory.

Why Isn't Supersymmetry Noticeable In Daily Life?

We don't notice any of this in everyday life, or even in high energy physics experiments (if the theory is true) because all of the particles created by supersymmetry except one (which explains dark matter and interacts with other matter no more strongly than neutrinos do) are unstable and decay into ordinary matter before we have time to see it, and also because they only form at all in very high energy situations.

If this sounds familiar, it should. Most of the particles we do know exist decay extremely rapidly into ordinary matter and only form at all in very unusual high energy situations, or are always found confined in composite particles and never seen in isolation, or are neutrinos which are extremely hard to detect because they interact so weakly with everything else.

In daily life, we see mostly protons and neutrons (which are made mostly out of up quarks and down quarks bound together by gluons so tightly that we never see free quarks or free gluons), electrons, and photons.  The force that connections protons and neutrons in the nucleus of an atom is carried mostly by pions which are made up of two up and down quarks bound by gluons which are themselves short lived and travel only short distances before decaying (with the quarks and gluons never visible in isolation).  All other particles in the Standard Model are too ephemeral or ghostlike to notice without high technology instrumentation in carefully constructed lab experiments.  

The vast majority of physics (except radioactivity and high energy physics) can be explained with protons, neutrons, pions, electrons and photons (the first three of which are not actually fundamental), without knowing about the huge menagerie of fundamental particles and composite particles needed to describe the last 0.1% of reality.

Supersymmetry just adds more exotic, ephemeral fundamental particles and particles that are very hard to detect (a dark matter candidate called a WIMP) to the mix for relative obscure theoretical reasons set forth in the next section.

Why Supersymmetry?

Supersymmetry is attractive as a theory for many reasons, some of which are now obsolete:

(1) It provides natural candidates for dark matter particles of a variety called "WIMPS".

(2) It makes the constants of the Standard Model such as the Higgs boson mass seem more "natural".

(3) It makes it much easier to do math that sheds light on how particles interact at very high energy, because the balance between fermions and bosons makes lots of terms in calculations that would otherwise have to be calculated cancel out.

(4) It unified the three fundamental forces into one master force at high energies called the GUT scale.

(5) It provides a way to explain where the matter in the universe came from that are unexplained in the Standard Model.

(6) It sheds some light on the kind of reasons that Standard Model constants might have the values they do although not particular clear guidance.

(7) Supersymmetry is so mathematically similar to the Standard Model of particle physics, it is easy to tweak properties of particular versions of supersymmetry like particle masses in such a way that it predicts essentially the same things as the Standard Model down to the limits of experimental error. So it is hard to reject outright.

(8) Before we knew the mass of the Higgs boson, lots of Standard Model predictions in high energy situations were nonsense answers where the likelihood of all possible events didn't add up to 100% if Higgs boson mass is not just right, but this doesn't happen in supersymmetry.  This is less of a big deal than it used to be because the mass of the recently discovered Higgs boson is "just right" and prevents the Standard Model from becoming pathological mathematically at high energies in the way that it would if the Higgs boson where much heavier or much lighter than it is in reality. 

(9) Supersymmetry is also a very natural low energy approximation of string theory.  Many versions of string theory require, for mathematical reasons, that fundamental fermions and fundamental bosons have counterparts for each other for reasons related to the way a fundamental superstring in that theory can vibrate.

Theoretical physicists are very reluctant to abandon supersymmetry because that would mean giving up hope that their best shot at a good theory of quantum gravity through string theory as explained below. So they'd have to start over from scratch trying to merge quantum mechanics and general relativity. 

Why String Theory?

The Standard Model and general relativity are mathematically incompatible with each other. The reasons that the Standard Model (i.e. quantum mechanics) and general relativity are incompatible are quite mathematical and technical but include, for example, the fact that point particles which are assumed in quantum mechanics would instantly turn into black holes in general relativity.

The Standard Model and supersymmetry are both fully compatible with special relativity, however.

Scientists from Einstein onward have been trying very hard to unify gravity and other forces of nature ever since general relativity and quantum mechanics were conceived in the early 1900s. So far, no one has even come close to succeeding.

A potential connection to string theory is attractive because string theory offers a reasonable hope that it could provide a mathematically consistent way to create a theory of quantum gravity that could be consistent with the rest of quantum mechanics which is called the Standard Model. 

String theory is pretty much the only game in town that creates a potential theory of quantum gravity with particle based force fields like those used in the rest of quantum mechanics so it is very tempting to find a way to connect what we know to it.

There is another approach to quantum gravity that involves applying quantum mechanical concepts to the nature of space-time itself, which includes approaches known as Loop Quantum Gravity (LQG), rather than using the force field carried by particles approach of string theory, but that is a story for another day that doesn't involve supersymmetry.

Why Not Supersymmetry?

The obvious problem with supersymmetry is that nobody has ever seen any of the supersymmetric particles, either because they are not real, or because the new particles are simply too heavy to see in colliders, or because they are otherwise not visible due to something called "R-parity" (a property that basically keeps sparticles and regular matter separated).

(1) If superpartners exist, the LHC has determined that they are much heavier than they were expected to be.  At some point, if they are not found at low enough masses, they would be so heavy that they would lead to predictions that are contrary to experimental evidence.

(2) "Naturalness" which is an important reason for supersymmetry is being questioned as a useful theoretical concept.

(3) The evidence of force unification that should have showed up by now has not appeared.  

(4) And, the LUX experiment has pretty much ruled out the kinds of WIMP dark matter particles that supersymmetry predicted.

Why Not String Theory?

String theory has all of the problems of SUSY and SUGRA and also lots of problems of its own. Basically, there are thousands or millions or more versions of string theory (called "vacua") and nobody knows which version is remotely close to our reality.

Where Does This Leave Us?

The Standard Model, in contrast, has no obvious generalizations that could for example be used as a basis for a version of string theory. So figuring out how to meld it with quantum gravity is even more difficult.

Coming Attractions

The latest results from the LHC on the 750 GeV "bump" in the data is scheduled to be released at a conference which begins on August 3, 2016, a week from yesterday.

This "bump" which now appears to have been nothing more profound than a statistical fluke, spawned intense interest from the theoretical physics community that resulted in publication of more than five hundred journal article pre-prints in the span of just a few months (see also here in a post at this blog of the same name as this one).

The rumor mill has it that the results will not involve a 5 sigma "discovery" threshold finding and will probably show declining statistical significance.  Indeed, the rumor is that the 750 GeV "bump" is basically dead (as I predicted it would be on this blog when the results were first announced). But, of course, we'll have a far more precise answer soon.

The minimal model of the Standard Model together with General Relativity with a cosmological constant continues to reign supreme, explaining pretty much everything except dark matter phenomena.  Light sterile neutrinos are essentially ruled out too.

Add to this the failure of direct detection experiments and of satellites trying to detect dark matter annihilation signatures (and a lot of other data) is putting tight constraints on any particle based dark matter solution and ruling out conventional SUSY WIMPS.  Not all dark matter particles are ruled out yet, however, and no really wholeheartedly convincing true quantum gravity theory to explain dark matter phenomena is in place either, even though some intriguing efforts has been made on that front.

Ashkenazi Jewish Genetics

Most Jews are either Ashkenazi Jews or Sephardic Jews, and most American Jews are Ashkenazi Jews, typically with origins someplace in Eastern Europe immediately prior to immigration to the United States.

A new paper looks at the genomes of Ashkenazi Jews today in order to determine their population history using computerized tools and a greatly expanded set of Jewish and non-Jewish reference genomes that has accumulated over the last few years. 

This is necessary because the historical record provides very little meaningful or reliable insight into the process by which the Jewish diaspora resulted in migrations of Jews from the Middle East to Europe. The gap in the historical record is particularly acute in the several century long gap period after the composition of the Babylonian Talmud and the fall of the Roman Empire, and before the pogroms directed at Jews in Europe which roughly coincided with the Crusades. Yet, this gap period was apparently the period of Ashkenazi Jewish ethnogenesis and the source of the population bottleneck that is a defining feature of Ashkenazi Jewish population genetics.

The quaint term for this time period in historical circles is the "dark ages" and the dearth of historical sources from that era deserve that name, even though we do know a fair amount about that time period now by a variety of means. This time period overlaps with the expansion of the Islamic empire, the Slavic expansion in Eastern Europe, the "migration period" of (mostly) Germanic tribes in Europe, and Anglo-Saxon and Viking raids into and migration of England (which is arguably part of the migration period).

The genetic analysis is not straightforward because (1) there are considerable similarities between the genetic profiles of the suspected source populations, (2) there is little ancient DNA to bear on the question very directly, and (3) modern populations are not great proxies of historical populations at the time that the relevant stages of the migrations happened, particularly in the Levant and Slavic Europe. Indeed, the latest results come with considerable acknowledged uncertainty, although the broad outlines of the analysis are probably correct.

The West Hunter blog has a summary of the findings of this open access paper that fairly states the conclusions of the paper at least as well as I could describe them myself:

When they analyze the origins of the European component of Ashkenazi ancestry, they conclude that most is southern – probably Italian, but that smaller amounts originated from (probably) Western Europe and (more certainly) Eastern Europe: and in that temporal order. They conclude that the Italian admixture slightly predated a late medieval founder event. Different methods came up with somewhat different estimates for the total amount of European ancestry: the local ancestry inference (LAI) approach came up with 53% European, while the GLOBETROTTER analysis came up with an estimate of 67% European ancestry (after calibration by simulations). In their best guess, they split the difference and go for 60% European.

To sum up, their model is that a population from the Levant mixed with Italians, and shortly thereafter moved to the Rhineland (the founding bottleneck), perhaps mixing to some degree with the local Europeans there, and certainly mixing some with Slavic types when they moved to the Polish-Lithuanian Commonwealth.

How do their conclusions differ from those in the last report? Previously they were thinking that the bottleneck was around 1350, a product of the Black Death and savage persecution – now they’re talking the original settlement in the Rhineland. Previously they had a somewhat lower estimate of European ancestry (~48%, now 60%). I thought these two conclusions likely a couple of years ago. 

The big new point, important if correct, is that the admixture with Italians is relatively recent – too recent to have happened back in Roman times. In their model, this main admixture event is 25-55 generations ago, while the founding bottleneck is 25-35 generations ago. It’s not impossible that the admixture happened at the same time as the founding.

About 15%-25% of Ashkenazi Jewish ancestry, which is a quarter to a almost half or so of the total European ancestry, is Eastern European.  I've also seen other sources conclude that the paternal line is more strongly Levantine than Jewish maternal ancestry.

As Razib Khan has noted in comments to his post on the same paper, the Black Plague hypothesis was always suspect as a source of the population bottleneck that is clearly apparent in Ashkenazi Jewish population genetics, because it didn't kill a large enough percentage of the population to be likely to have caused the observed bottleneck effects.

This is also as good a post as any to observe that all Jewish populations in the world from Ashkenazi and Sephardic Jews to Jews in Yemen, India and elsewhere, are significantly admixed with local populations. Endogamy in the founding populations of Jews in the Jewish diaspora has almost always been modest in the founding period, even though these barriers to admixture ossified with time. There are probably far fewer "pure blooded" Jews with exclusively Levantine origins and descended from Jews in their Iron Age kingdoms (I'm not convinced that there are any), than there are "pure blooded" Native Americans who lack European or African admixture, for example.

Lux Further Constrains Dark Matter Parameter Space By A Factor Of Four

Lux is the gold standard for direct dark matter detection experiments and has further ruled out forms of dark matter that slightly interact with ordinary matter to a much greater degree.  Any dark matter particles with masses from 1 GeV to 10,000 GeV that have interactions with ordinary matter that are more than a fraction of the strength of interactions of a neutrino (which is barely any at all) have been ruled out.

The WIMP paradigm (in the narrow sense of dark matter particles that interact via both the weak force and gravity) is well and truly dead.

From Quantum Mechanics To Gravity

Sean Carroll's latest paper considers (but doesn't really prove) a couple of interesting conjectures:

1. Gravity and space-time geometry are emergent properties of a quantum world that reflect the degree to which particles are entangled with each other (more entanglement implies shorter distances and the mass-energy coupling might emerge more or less naturally and automatically from the formulation).

2. Nature is a quantum system in a finite dimensional Hilbert space, rather than an infinite dimensional Hilbert space as generally assume in quantum mechanics, which would provide a natural (but elegant) cutoff that would insulate the real world from the infinities and singularities found in quantum mechanics and GR done in an infinite dimensional/continuous approximation.

More On Madagascar's Genetic Origins

The biggest surprises of a new paper on the genetic origins of the people of Madagascar are the roughly 2/3rds African origin demonstrated when some previous estimates had been closer to 35%-50%, and more surprisingly, that the affinity of that African component to Southern African Bantu, when previous data had rejected that hypothesis in favor of an affinity to East African Bantu populations (less some recent Nilo-Saharan admixture).

Southern African Bantu have a substrate of pre-Bantu Mozambique people which is very distinctive from any extant African population to the extent that it basically constitutes a "lost race" of Africans that coincides with linguistic substrates of Bantu languages in that region indicating that the pre-Bantu people of Mozambique spoke a click language.  There are also uniparental markers private to Mozambique that are largely absent from Madagascar.  So, there are strong reasons to be skeptical of a Southern African as opposed to East African source for the African genetic contribution to Madagascar.

The lack of a strong historical connection between Mozambique across the strait from Madagascar and that island is likewise demonstrated by a lack of archaeological support for those kinds of trade ties and a lack of Southeast Asian genetic traces in mainland Africa (anywhere).

The conclusions on the Asian genetic origins side of the analysis, on the other hand, are plausible and very consistent with previous research on the topic, although the analysis does not identify indications from previous studies that the migration was probably along the Indian Ocean's coast with stops in South Asia and East Africa, rather than directly across the Indian Ocean as a graphic in the new paper misleadingly suggests.

I'll need to look more closely at the various papers involved to see if these new results can be reconciled with the prior research, and if not, to determine the likely source of the disparity.  The two-thirds percentage is probably right, but the South African Bantu affinity seems suspect. The fact that only the Asian conclusions and not the controversial African ones end up in the abstract of the paper is also notable.

The pertinent portion of the paper addressing this point states:

The admixture profile of our dataset (2183 individuals from 61 populations genotyped for 40,272 SNPs; Supplementary figures S2 and S3, Supplementary Material online), based on ADMIXTURE analyses (Alexander, et al. 2009), shows that the Malagasy genetic diversity is best described as a mixture of 68% African genomic components and 32% Asian components, corresponding well with the results of previous studies (Capredon, et al. 2013; Pierron et al. 2014). While the African ancestry component in Malagasy appears to be broadly similar to that still present today in South African Bantu, the Asian ancestry presents a more complex pattern. . . . to more specifically identify the Asian ancestry of the Malagasy genome, we performed a Local Ancestry analysis with PCAdmix (Brisbin, et al. 2012) using two proxy parental meta-populations comprising 100 individuals with African ancestry (randomly selected from Yoruba, South African Bantu, Kenyan Luhya and Somali groups) and Asian ancestry (randomly selected from Chinese, Philippine Igorot, Bornean Ma’anyan and Malay groups). . . . To expand on this, however, we inferred the population sources of the Malagasy, their relative ratios and the dates of potential admixture events with GLOBETROTTER (Hellenthal, et al. 2014), defining each population in our dataset as a donor/surrogate group and the Malagasy as the recipient, using the haplotype ‘painting’ data obtained with Chromopainter (Lawson, et al. 2012). The best fit outcome for the Malagasy was obtained under a model of a single admixture event between two sources: the Banjar representing 37% of modern Malagasy and the South African Bantu population representing the other 63% (r2 =0.99, P<0.01; Figure 2 and Supplementary table S5, Supplementary Material online). The admixture event was dated to 675 years BP (95% CI: 625-725 years BP, Supplementary table S5, Supplementary Material online), which is similar to the dates of admixture estimated by ALDER (550-750 years BP) using Banjar population in combination with the South African Bantu (Supplementary table S6, Supplementary Material online)(Loh, et al. 2013). When each Malagasy ethnic group is analysed separately, similar parental populations, admixture proportions and dates are obtained with the noticeable older by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from estimated dates towards the east coast of Madagascar (Supplementary table S5, Supplementary Material online). Crucially, these dates of genetic admixture, in agreement with a previous study (Pierron et al. 2014), reflect the midpoint or end of noticeable admixture between groups of Asian and African ancestry in Madagascar, rather than the start of this contact. Therefore they could correspond to the end of the period of the main Austronesian presence in Madagascar that started around the first millennium CE (Dahl 1951, 1991; Dewar and Wright 1993; Adelaar 1995; Cox et al. 2012; Adelaar forthcoming). On the other hand, around 1100-700 years BP, climatic changes in the South of Africa forced Bantu populations to move to more hospitable places (Huffman 2000). This South Bantu migration has previously been suggested as an explanation for the higher density of populations observed in the South of Madagascar (Beaujard 2012a). As all of our sampled groups live in the South of Madagascar, and considering that the estimated dates of admixture are more recent on the west coast (Supplementary tables S5 and S6, Supplementary Material online), it is tempting to interpret our admixture date as marking the last significant Bantu migration to Madagascar, perhaps initiated by climatic changes in Africa.

Suffice it to say that the analysis of the African side of the genetic contribution is shallow and does not rigorously compare competing hypotheses of African contributions.

The Supplemental Materials indicate that the African samples other than South African Bantu come from International HapMap, et al. (2010) (i.e. Integrating common and rare genetic variation in diverse human populations. Nature 467: 52-58. doi: 10.1038/nature09298) and Pagani, et al. (2012) (i.e. Ethiopian genetic diversity reveals linguistic stratification and complex influences on the Ethiopian gene pool. Am J Hum Genet 91: 83-96. doi: 10.1016/j.ajhg.2012.05.015). The South African Bantu sample comes from May, et al. (2013) (Genetic diversity in black South Africans from Soweto. BMC Genomics 14: 644. doi: 10.1186/1471-2164-14-644).

Another data set of Southeastern Bantu speakers referenced in May, et al. (2013) seems to overlap with the Soweto sample and derives from Schlebusch, et al., "Genomic variation in seven Khoe-San groups reveals adaptation and complex African history." Science. 2012, 338: 374-379.

It is also possible that Soweto Bantus are very genetically distinct from Mozambique Bantus and may be more similar to ancestral East African Bantus than modern East African Bantus, because they may lack subsequent Nilo-Saharan Ancestry and may, in general have less of a substrate influence.

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

Malagasy genetic diversity results from an exceptional proto-globalisation process that took place over a thousand years ago across the Indian Ocean. Previous efforts to locate the Asian origin of Malagasy highlighted Borneo broadly as a potential source, but so far no firm source populations were identified. Here, we have generated genome-wide data from two Southeast Borneo populations, the Banjar and the Ngaju, together with published data from populations across the Indian Ocean region. We find strong support for an origin of the Asian ancestry of Malagasy among the Banjar. This group emerged from the long-standing presence of a Malay Empire trading post in Southeast Borneo, which favoured admixture between the Malay and an autochthonous Borneo group, the Ma’anyan. Reconciling genetic, historical and linguistic data, we show that the Banjar, in Malay-led voyages, were the most probable Asian source among the analysed groups in the founding of the Malagasy gene pool.

Brucatol, et al., "Malagasy genetic ancestry comes from an historical Malay trading post in Southeast Borneo." 33 (7) Molecular Biology and Evolution (July 5, 2016).

The literature cited is as follows (and admittedly includes some other papers I haven't yet seen):

* Adelaar A. 2009a. Towards an Integrated Theory about the lndonesian Migrations to Madagascar. In. Ancient human migrations: a multidisciplinary approach.: University of Utah Press

* Adelaar KA. 1995. Borneo as a cross-roads for comparative Austronesian linguistics. In: Canberra AAEP, editor. The Austronesians: historical and comparative perspectives. p. 81–102.

* Adelaar KA. 2009b. Loanwords in Malagasy. In: Haspelmath M, Tadmor U, editors. Loanwords in the world’s languages: a comparative handbook. Berlin, Germany: De Gruyter Mouton. p. 717-746.

* Adelaar KA 1989. Malay influence on Malagasy: linguistic and culture-historical implications. Oceanic Linguistics 28: 1-46. doi: 10.2307/3622973

* Adelaar KA. forthcoming. Who were the first Malagasy, and what did they speak? In: Acri A, Landmann A, editors. Cultural Transfer in Early Monsoon Asia. Singapore: Institute of Southeast Asian Studies.

* Alexander DH, Novembre J, Lange K 2009. Fast model-based estimation of ancestry in unrelated individuals. Genome Research 19: 1655-1664. doi: 10.1101/gr.094052.109 by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from Beaujard P. 2012a. Les mondes de l’ocean indien. Vol. 2 : L’océan Indien, au cœur des globalisations de l'Ancien Monde (7e-15e siècles). Paris, France: Armand Collin. Beaujard P. 2012b. Les mondes de l’océan Indien. Vol. 1 : De la formation de l’État au premier système-monde afro-eurasien (4e millénaire av. J.-C.-6e siècle apr. J.-C.). Paris, France:

* Armand Collin. Brisbin A, Bryc K, Byrnes J, Zakharia F, Omberg L, Degenhardt J, Reynolds A, Ostrer H, Mezey JG, Bustamante CD 2012. PCAdmix: Principal componentsbased assignment of ancestry along each chromosome in individuals with admixed ancestry from two or more populations. Human Biology 84: 343-364. doi: 10.3378/027.084.0401

* Capredon M, Brucato N, Tonasso L, Choesmel-Cadamuro V, Ricaut F-X, Razafindrazaka H, Rakotondrabe AB, Ratolojanahary MA, Randriamarolaza L-P, Champion B, Dugoujon J-M 2013. Tracing arab-islamic inheritance in Madagascar: Study of the Y-chromosome and mitochondrial DNA in the Antemoro. PLoS One 8: e80932. doi: 10.1371/journal.pone.0080932

* Cox MP, Nelson MG, Tumonggor MK, Ricaut F-X, Sudoyo H 2012. A small cohort of Island Southeast Asian women founded Madagascar. Proceedings of the Royal Society B: Biological Sciences 279: 2761-2768. doi: 10.1098/rspb.2012.0012

* Dahl OC 1951. Malgache et maanjan: une comparaison linguistique. Oslo, Norway: Edege-Intituttet.

* Dahl OC 1991. Migration from Kalimantan to Madagascar. Oslo, Norway: Norwegian University Press : Institute for Comparative Research in Human Culture.

* Dewar RE, Wright HT 1993. The culture history of Madagascar. Journal of World Prehistory 7: 417-466. doi: 10.1007/BF00997802 by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from Fourquet R, Sarthou J, Roux J, Aori K 1974. Hemoglobine S et origines du peuplement de Madagascar: nouvelle hypothese sur son introduction en Afrique [Hemoglobin S and origins for the settlement of Madagascar: new hypothesis on its introduction to Africa]. Arch. Inst. Pasteur Madagascar 43: 185–220.

* Fuller DQ, Boivin N, Hoogervorst T, Allaby R 2011. Across the Indian Ocean: the prehistoric movement of plants and animals. Antiquity 85: 544-558.

* Hellenthal G, Busby GB, Band G, Wilson JF, Capelli C, Falush D, Myers S 2014. A genetic atlas of human admixture history. Science 343: 747-751. doi: 10.1126/science.1243518

* Hewitt R, Krause A, Goldman A, Campbell G, Jenkins T 1996. beta-globin haplotype analysis suggests that a major source of Malagasy ancestry is derived from Bantu-speaking Negroids. Am. J. Hum. Genet. 58: 1303–1308.

* Huffman TN. 2000. Mapungubwe and the origins of the Zimbabwe culture. In: Leslie M, Maggs T, editors. African naissance: The Limpopo valley 1000 years ago. Cape Town, South Africa: South African Archaeological Society. p. 14-29.

* Hurles ME, Sykes BC, Jobling MA, Forster P 2005. The dual origin of the Malagasy in Island Southeast Asia and East Africa: evidence from maternal and paternal lineages. Am J Hum Genet 76: 894-901.

* Kusuma P, Brucato N, Cox MP, Pierron D, Razafindrazaka H, Adelaar A, Sudoyo H, Letellier T, Ricaut F-X 2016. Contrasting Linguistic and Genetic Influences during the Austronesian Settlement of Madagascar. Scientific Reports 6:26066. doi: doi: 10.1038/srep26066

* Kusuma P, Cox MP, Pierron D, Razafindrazaka H, Brucato N, Tonasso L, Suryadi HL, Letellier T, Sudoyo H, Ricaut F-X 2015. Mitochondrial DNA and the Y by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from chromosome suggest the settlement of Madagascar by Indonesian sea nomad populations. BMC Genomics 16: 191. doi: 10.1186/s12864-015-1394-7

* Lawler A 2014. Sailing Sinbad's seas. Science 344: 1440-1445. doi: 10.1126/science.344.6191.1440

* Lawson DJ, Hellenthal G, Myers S, Falush D 2012. Inference of population structure using dense haplotype data. PLoS Genet 8: e1002453. doi: 10.1371/journal.pgen.1002453

* Loh PR, Lipson M, Patterson N, Moorjani P, Pickrell JK, Reich D, Berger B 2013. Inferring admixture histories of human populations using linkage disequilibrium. Genetics 193: 1233-1254. doi: 10.1534/genetics.112.147330

* Patterson N, Price AL, Reich D 2006. Population structure and eigenanalysis. PLoS Genet 2: e190. doi: 10.1371/journal.pgen.0020190

* Patterson NJ, Moorjani P, Luo Y, Mallick S, Rohland N, Zhan Y, Genschoreck T, Webster T, Reich D 2012. Ancient admixture in human history. Genetics 192: 1065-1093. doi: 10.1534/genetics.112.145037

* Pickrell JK, Pritchard JK 2012. Inference of population splits and mixtures from genome-wide allele frequency data. PLoS Genet 8: e1002967. doi: 10.1371/journal.pgen.1002967

* Pierron D, Razafindrazaka H, Pagani L, Ricaut F-X, Antao T, Capredon M, Sambo C, Radimilahy C, Rakotoarisoa J-A, Blench RM, Letellier T, Kivisild T 2014. Genome-wide evidence of Austronesian–Bantu admixture and cultural reversion in a hunter-gatherer group of Madagascar. Proceedings of the National Academy of Sciences 111: 936-941. doi: 10.1073/pnas.1321860111

* Ras JJ. 1968. Hikajat Banjar: a study in Malay historiography. The Hague: Martinus Nijhoff. by guest on July 12, 2016 http://mbe.oxfordjournals.org/ Downloaded from Serva M, Petroni F, Volchenkov D, Wichmann Sr 2012. Malagasy dialects and the peopling of Madagascar. Journal of the Royal Society Interface 9: 54-67. doi: 10.1098/rsif.2011.0228

* Soodyall H, Jenkins T, Hewitt R, Krause A, Stoneking M. 1996. The peopling of Madagascar. In: Boyce A, Mascie-Taylor C, editors. Molecular biology and human diversity. Cambridge, UK: Cambridge University Press. p. 156–170.

* Tofanelli S, Bertoncini S, Castri L, Luiselli D, Calafell F, Donati G, Paoli G 2009. On the origins and admixture of Malagasy: new evidence from high-resolution analyses of paternal and maternal lineages. Mol Biol Evol 26: 2109-2124.

Evidence Increasingly Rules Out Light Sterile Neutrino Hypothesis

The Standard Model of Particle Physics includes three flavors of neutrinos - electron neutrinos, muon neutrinos and tau neutrinos, so named because particle physicists weren't feeling particularly creative when they were hypothesized (and ultimately discovered).

There needs to be a neutrino counterpart to each charged lepton to preserve the approximate lepton flavor conservation symmetry of the theory (neutrino oscillation prevents it from being a perfectly conserved symmetry), and weak force boson decays have long confirmed that there are three flavors of weakly interacting neutrinos, so three flavors of neutrinos are necessary to make electroweak theory conform to observation.

Anomalies in reactor neutrino data had suggested the possibility of a fourth light neutrino that oscillates with the three ordinary neutrinos, but do not interact via the weak force.

The cosmologically measured constant Neff (effective N) for the number of neutrino flavors increasingly disfavors a fourth type of neutrino that the existing three flavors oscillate with (but which does not interact via the weak force). So do new cosmological data bounds on the sum of the mass of all neutrino flavors because the difference between the maximum value of the sum of the masses of the three neutrino flavors and the minimum value derived from the differences in mass between the three primary neutrino mass states is increasingly small, placing an upper bound on the mass of any fourth sterile neutrino.

(Note, however, that the cosmology purposes, a neutrino with a mass far in excess of 1 eV/c^2 such as a sterile neutrino with a mass on the order of a keV, which has been proposed as a dark matter candidate, is outside the cosmology definition of a neutrino. The cosmology definition is largely synonymous with the definition of "hot dark matter", rather than using the usual Standard Model definition.)

This year's Neutrino 2016 Conference has produced three papers all documenting new experimental findings the strongly disfavor the kind of sterile neutrino that is light enough and mixed enough with the other three neutrino flavors to explain the apparent reactor neutrino anomalies that had prompted the light sterile neutrino hypothesis. One of the papers setting for the new experimental limits is based on data from the Daya Bay experiment, one is based on MINOS data, and one combines data from the Daya Bay, MINOS and Bugey-3 experiments to obtain a global exclusion based upon the latest data.

Taken together, the cosmology and earth based experimental exclusions provide a strong and robust exclusion of the light sterile neutrino hypothesis in all circumstances in which any other evidence might have suggested it in the first place (and the reactor anomaly itself have also grown less acute as more data and analysis have examined it).

Also, the titles and abstracts of the papers on neutrinoless double beta decay this year make clear that nobody has credibly observed neutrinoless double beta decay yet experimentally, so the experimental minimum bound on the potential mean time frame of neutrinoless double beta decay continues to get incrementally longer from the last time this data was reported.  No instances of lepton number violation have been observed in any other context either.

Gravitationally Bound Composite Neutrino Structures?

The following abstract describes a poster presentation at the Neutrino 2016 Conference that is currently in progress (July 4-9) in South Kensington, England:

Poster session 3 – Wednesday 6 July

P3.037 Gravitationally confined relativistic neutrinos

C Vayenas1,2, A Fokas3,4 and D Grigoriou1

1University of Patras, Greece, 2Division of Natural Sciences, Greece, 3University of Cambridge, UK, 4University of Southern California, USA

Combining special relativity, the equivalence principle and Newton’s universal gravitational law with gravitational rather than rest masses, one computes that gravitational interactions between relativistic neutrinos with kinetic energies above 10 MeV are very strong and can lead to formation of gravitationally confined composite structures. One may model the formation of such composite structures by considering three neutrinos moving symmetrically on a circular orbit under the influence of their gravitational attraction, and by assuming quantization of their angular momentum, as in the Bohr model of the H atom. The model contains no adjustable parameters and its solution leads to composite state radii close to 1 fm and neutrino velocities so close to c, that the corresponding Lorentz factor, gamma, values are of the order of 5*10⁹. 

It is thus found that when the neutrino rest masses are of the order of 0.05 eV/c2, then the mass, 3(gamma)m_o, of such three rotating neutrinos structures is very similar to that of hadrons (~ 1 GeV/c2). The thermodynamics of the phase condensation of neutrinos to form such structures are compared with QCD calculations for the quark-gluon condensation temperature.

Using the same approach we find that the mass of relativistic rotating Ve – e+/- pairs is 81 GeV/c2, close to that of W+/-bosons.

The W boson coincidence is particularly interesting.  Another interesting poster considers a possible gravitational source for neutrino mass.

Boya and Rivera have reviewed a number of similar theories.

Service Interruption

I am in the midst of representing clients in two long, back to back trials, as the lawyer who was to be doing what has become my job in one of them is on his honeymoon.  One, to a jury, is so far four days past its scheduled conclusion. I'll come up for air when they're finished, which may be another week or so.

John Hawks On Neanderthal Stone Circles

John Hawks muses at length on Neanderthal stone circles recently discovered deep in a cave. His main point is that given that much smaller average population of Neanderthals at any one time, and their greater remoteness in history, it isn't surprising that the archaeological record that might shed light on their culture is thin.

More Quick Hits

* Celtic parts of the U.K. (presumably Scotland, Wales, Northern Ireland), have more steppe ancestry than Southern and Eastern England proper, presumably because Norman invaders ca. 1066 CE had less steppe ancestry than the pre-existing residents of the U.K.  The residents of English proper also have less steppe ancestry than Anglo-Saxon ancient DNA.  Keep in mind, however, that this is a subtle difference that is discernible only because of a huge sample size (N=113,851) in a generally very homogeneous population.

* 48 ancient genomes from Iron Age to 18th century Finland will be available before year end.

Ancient Phoenician mtDNA Looks European

The mito-genome of a Carthaginian Phoenician has been sequenced...The Tunisia man had the maternal haplotype U5b2c1, which is fairly limited to Europe. It is also found in low frequency in the Phoenician heartland of Lebanon, which was either native there as well or it was cross-pollinated through its colonies in Western and Southern Iberia. Additional sequencing shows some affinity to a person from Portugal.

From Bell Beaker Blogger.

Trying To Mix Physics and Religion Can Get Embarassing

Letting money from religiously motivated people drive discussions of physics can lead to absurd crazy-talk.

Some people at Rutgers have decided to show what can go wrong when you have the Templeton Foundation funding “philosophy of physics”. They’ve scheduled a two-day Rutgers Mini-Conference on Multiverse, Theodicy, and Fine-Tuning, during which the speakers will consider the following two topics:

• Everettian Quantum Mechanics and Evil

  The problem of evil has been around for a long time: How can an all-powerful and all-good God allow evil of the sorts we see in the world? If the Everettian interpretation of quantum mechanics is correct, though, then there is a lot more evil in the world than what we see. This suggest a second problem of evil: If Everettianism is true, how can an all-powerful and all-good God allow evil of the sort we don’t see?

• A Probability Problem in the Fine-Tuning Argument
  

  According to the fine-tuning argument: (i) the probability of a life-permitting universe, conditional on the non-existence of God, is low; and (ii) the probability of a life-permitting universe, conditional on the existence of God, is high. I demonstrate that these two claims cannot be simultaneously justified.

From Not Even Wrong.

For those of you who aren't familiar with it, the Everettian interpretation of quantum mechanics is another name for the "Many Worlds Interpretation".

The "fine-tuning" argument argues that physical constants in our current version of the laws of the universe which are derived from a variety of other physical constants, must have precise and absurdly "unlikely" values to cancel out and produce the measured values.

Every now and then I consider absurd questions too, like whether unicorn meat would be kosher. But, I don't try to hold legitimate academic mini-conferences discussing the issue.

Quick Hits

Busy with work and fighting an eight week old spring cough, so I'll be brief:

* Ny's arya blog has an interesting post about the linguistic evidence that the proto-Indo-European homeland had lots of tall mountains, contra the stereotype of proto-Indo-Europeans as purely steppe people.  Likewise, there is lots of sedentary agricultural vocabulary in proto-Indo-European.

This blog also pointed me to a nice meaty article (pdf) on the latest thinking about the Tocharian languages (the easternmost and now extinct branch of the Indo-European languages) by J.P. Mallory, a leading expert in the field.

* There is a new linguistics paper on Dene-Yeniseic by the main proponent of the case that the two language families (one Old World and one New World) are linguistically related.

* Someone found a beer recipe from China ca. 3000 BCE.

* Corded Ware women were more mobile than men per Strontium analysis of remains.

* British Bell Beaker people were mobile within Britain but not so much beyond it. Many more findings from the same paper are discussed here.  And, Beaker people were all over the British Isles:

* In the course of a discussion at Razib's blog over whether Muhammed could have been a Christian or Christian influenced, I did some research on and learned a lot about the Parthian Empire which is relevant to a lot of Iron Age history.  The discussion by Razib, me and multiple others is worth reading and brings out both stark differences of opinion in fact, subtle differences of opinion on importance and characterization of the facts, and plain old lots of historical data points from all sides that you probably didn't hear about, or don't recall, from Western Civ.  My usual focus is pre-Iron Age, but I'm intrigued enough to look more closely into this period.

* I've been largely convinced that you can't meaningfully estimate how many genes influence a continuous genetically determined trait by looking at the genetic variance and assuming that due to the law of averages, if a trait is determined by a large number of genes then it will have low variance in a population.  This is true, at the most basic level, because the law of averages applies only to repeated trials with the same probability and effect, while additive genetic variance does not meet this condition.

* Analysis of whole genomes from all over the world by software that allows for admixture tend to show that South Asians and East Eurasians mostly descend from West Africans with material East African admixture.  But, its hard to know what to make of that as the software is really operating to deal with issues beyond the range of applicability where it is designed to function properly and can't necessarily consider all hypotheses that make sense to explain the data.

* Humans were hunting mastodons in Florida ca. 14,550 years ago (pre-Clovis).

* Fifteen Indus River Valley civilization remains have been sent to labs for ancient DNA analysis and someday we'll learn what they can tell us about that civilization whose population genetic connection with West Eurasia and South Asia is highly disputed.  But, it could take awhile.

* Brown bears and modern humans migrated to similar places over the last 40,000 years (pre-agriculture) based upon brown bear genetics. Mammoth herd migration and genetics are similar informative regarding Paleolithic era human migrations. See also data points on elk.

* Donkeys were late arrivals to Europe, but donkey remains were found from 2500 BCE in Iberia.

* Somebody has unearthed a Dutch Bell Beaker boardwalk along a river.

* Bronze Age instrument construction involved very long range trade networks and the instruments themselves were widely disperse.

* The geology of the Andaman Islands explained.

mtDNA R0 is Native to Arabia

A new paper makes a very solid case that mtDNA R0, which is the sister clade to mtDNA HV (which is the dominant West Eurasian and North African Berber mtDNA clade) has a source in Arabia.  It has maximum diversity there in addition to most clades being most common there.  R0 is mostly found in Arabia and to a lesser extent West Asia, but mtDNA R0a1 is found at low frequencies across Europe as well and it as well as mtDNA R0a2'3 dispersed in the Mesolithic a.k.a. Epipaleolithic a.ka. 17kya to 13kya or so.

The full story is more complicated but generally fits a Mesolithic dispersal from Arabia which would have served as a refuge during the Last Glacial Maximum ca. 20kya.

The subclade mtDNA R0a2b2 is strongly associated by location, proximity, and age with the Ethio-Semitic migration from Arabia to East Africa, while R0a2b1 which strongly overlaps with it geographically, could be part of the same migration but might be from an earlier wave of Arabian to East African migration as the clade is two and a half times older than R0a2b2 along with a couple of other rare mtDNA R0 clade of the same age.

A rare clade mtDNA R0a6 is found mostly in Pakistan, mostly in the Kalash, but single individuals with this clade have also been noted in Iran, Palestine and Italy.

Einstein Published Theory Of General Relativity 100 Years Ago Today

The details are here. The theory was presented at a conference presentation in November of 1915, but the paper was submitted in March of 1916 and was published on May 11, 1916. Astonishingly little has changed in the theory of gravity since then (there have been refinements and applications of it, but not many).

In other news, the LHC is up and running again after a weasel induced shutdown. Grad students have been put on weasel patrol to prevent a repeat of the shutdown.

For the nearest future, the plan is to have a few inverse femtobarns on tape by mid-July, which would roughly double the current 13 TeV dataset. The first analyses of this chunk of data should be presented around the time of the ICHEP conference in early August. At that point we will know whether the 750 GeV particle is real. Celebrations will begin if the significance of the diphoton peak increases after adding the new data, even if the statistics is not enough to officially announce a discovery. In the best of all worlds, we may also get a hint of a matching 750 GeV peak in another decay channel (ZZ, Z-photon, dilepton, t-tbar,...) which would help focus our model building. On the other hand, if the significance of the diphoton peak drops in August, there will be a massive hangover...

A Moment Of Silence For Marcus

His Online Icon (via Mad Magazine)

I never met Marcus in person, but I discussed physics with him at the Physics Forum bulletin board where he presided over the Beyond the Standard Model forum with a special focus on loop quantum gravity (as well as other areas of physics where we shared interests) on countless lengthy occasions for about twelve years and he was always a perfect gentleman while also having great insights into physics.  He was a great mentor and friend.  He joined the board about a year before I did and in that time made about 25,000 comments and started 757 discussion threads.

It is with a heavy heart that I report that he has died of cancer (Friday or thereabouts).  According to his son, "it was esophagus cancer -- we found out about it in September, but by that point it was advanced to a level where not much could be done. We tried anyway -- chemo, radiation, etc. But, well..."

It is a sad day worthy of a moment of silence to reflect on what we shared.  The world is less wonderful without him.

Higher Primates Mostly Went Extinct In Asia When India Crashed Into Asia

Primates (per Wikipedia) can be broken down into a number of clades, one of which is called Simiformes (aka "anthropoids") which excludes tarsiers, lemurs and lorises (the so called "lower primates"), but includes humans, chimpanzees, gorillas, orangutans, gibbons, Old World Monkeys and New World Monkeys.

A new study, cited below, out of China provides insights into why "higher primates" survived and evolved into various clades including humans in Africa, while they went extinct leaving only "lower primates" in Asia.

The key event took place 34 million years ago when the collision of the continental plate that is now the Indian subcontinent hit the rest of Asia resulting in climate changes that destroyed jungles that had been home to primates until then. "Lower primates" managed to survive in the less lush forests that remained, while "higher primates" could not survive without a thriving tropical jungle.

A sharply cooler and drier climate at that time, combined with upheavals of landmasses that forged the Himalayas and the Tibetan Plateau, destroyed many tropical forests in Asia. That sent surviving primates scurrying south, say paleontologist Xijun Ni of the Chinese Academy of Sciences in Beijing and his colleagues. New Chinese finds provide the first fossil evidence that the forerunners of monkeys, apes and humans, also known as anthropoids, were then largely replaced in Asia by creatures related to modern lemurs, lorises and tarsiers. . . . 

“The focal point of anthropoid evolution shifted at some point from Asia to Africa, but we didn’t understand when and why the shift occurred until now,” says paleontologist and study coauthor K. Christopher Beard of the University of Kansas in Lawrence.
But the scarcity of Asian primate fossils from that time relative to those from Africa leaves the matter unsettled. Egyptian sites in particular have yielded numerous primate fossils dating from around 37 million to 30 million years ago. 

Excavations from 2008 to 2014 in southern China produced 48 teeth, some still held in jaw fragments, from six new fossil primate species, Beard says. These primates were tree dwellers and had assembled in a region located far enough south to retain forested areas. The new finds provide a rare glimpse of Asian primates that managed to weather the climate shift. Fossil teeth of one ancient species look much like those of modern tarsiers. These tiny, bug-eyed primates now live on Southeast Asian islands. “Tarsiers are ‘living fossils’ that can trace their evolutionary history back tens of millions of years in Asia,” Beard says. 

Only one Chinese fossil primate comes from an anthropoid, Ni’s group concludes. The researchers classify that animal as part of a line of Asian anthropoids previously identified from roughly 40-million-year-old tooth and jaw fragments found in Myanmar, just across China’s southwestern border (SN: 10/16/99, p. 244). 

Only one other Asian site, in Pakistan, has yielded anthropoid fossils of comparable age to the Chinese finds. The Pakistan fossils consist solely of teeth. Asian anthropoids died out a few million years after the continent’s tropical forests began to shrink, Beard suspects. 

Investigators already knew that primates’ forest homes in Africa survived the ancient cool down better than those in Asia. 

The Chinese team also argues, with less definitive support, for an asian origin of higher primates around 55 million years ago. But, "Lemur and loris ancestors must have lived in equatorial Africa and Madagascar by 34 million years ago, as lemurs and loris relatives do today. . . . The oldest known primate fossils, from 56 million to 55 million years ago, come from Asia, Europe, Morocco and North America." So, it is much harder to determine where primates, in general, first evolved.

The new paper is:

X. Ni et al. "Oligocene primates from China reveal divergence between African and Asian primate evolution." 352 Science 673 (May 6, 2016).

Is The 750 GeV Resonance Real? I Don't Think So

Hundreds of papers have been written about an apparent 750 GeV diphoton resonance seen at some moderate significance by both of the LHC experiments which Lubos likes to call the Cernette.

These bare facts would suggest a boson rather than a fermion (since the spin of the decay products is even), probably of spin-0 or spin-2 (because spin-1 bosons can't decay to two photons), and an intermediate electrically charged state of an otherwise electrically neutral particle, so it can couple to photons.

A second round of experimental data earlier this year confirmed initial indications of a "bump" that was too mild to be sure evidence of a new particle, but could conceivable be one, with a possible secondary Z boson-photon bump at 375 GeV.

The data are inconclusive at this point on the question of whether this resonance is narrow or wide (resonances are graphed as bell curves with a peak at the mass of the particle and a width measured half way up the peak at nearby masses that corresponds to the mean lifetime of the particle).

This paper from January which was updated last week, makes the case for a 4 sigma local significance, before considering look elsewhere effects, resonance with a narrow width and spin-0 (that also couples to gluons and hence must have strong force color charge as well).  It notes that:

1. The required cross section to fit the anomaly reported by ATLAS is in tension with the 8 TeV results, as well as the required cross section to fit the CMS anomaly. 

2. Combining all data sets yields a local significance of ∼ 4.0σ for a 750 GeV spin-0 resonance produced through couplings to gluons or heavy quarks. While quoted statistical significances must be taken with a grain of salt, as they are obtained using binned data without inclusion of systematic errors, I find the combination yields a net increase in the statistical significance as compared to the ATLAS data alone.

3. The spin-2 interpretation is mildly disfavored compared to a spin-0 mediator. This is due to correlations in the photon momenta which results in a relative decrease in the ATLAS acceptance compared to CMS.

4. The combination of ATLAS and CMS 13 TeV data has a slight statistical preference for a spin-0 mediator with a natural width much smaller than the experimental resolution, as compared to the Γ = 45 GeV preferred by ATLAS alone. When the 8 TeV data is added, there is a slight statistical preference for a wide resonance over the narrow option, as it is easier to hide a wide resonance in the 8 TeV background. . . .

When considering the 750 GeV diphoton excess, the theoretical community must balance its natural exuberance with the recognition that the statistical size of the anomalies are very small. As a result, any further slicing of data will yield at best modest statistical preferences for the phenomenological questions that we in the community want answers to. That said, given that this excess is the most significant seen at the LHC since the discovery of the 125 GeV Higgs, and the resulting avalanche of theoretical papers which shows no sign of slowing, it is still a useful exercise to carefully analyze the available data and determine what we do – and do not – know at this stage. While there is some useful information to be gleaned from this exercise, we are fortunate that the continuation of Run-II will be upon us shortly.

From the existing data, we can conclude the following:

1. Explaining the anomaly through a spin-0 resonance is preferred over a spin-2 mediator, though this preference is less than 1σ in most cases.

2. Combining the 8 and 13 TeV data from ATLAS and CMS sets yields a ∼ 4.0σ statistical preference for a signal of ∼ 4(10) fb, assuming a narrow (wide) spin-0 resonance. This ignores the look-elsewhere effect, as discussed. Given that the significance of my fits to individual ATLAS and CMS data-sets are underestimates when compared to the full experimental results, it is possible that the actual statistical preferences are larger than these quoted values. However this would require a combined analysis performed by the ATLAS and CMS Collaborations.

3. The cross sections needed for the Atlas13, Cms13, and Cms13/0T data sets are incompatible at the two sigma level, though they agree in mass. The most straightforward reading of this (while maintaining a new physics explanation for the anomalies) is that the larger Atlas13 cross section constitutes a modest upward fluctuation from the “true” cross section, which is more in line with the Cms13 value. The reverse is also possible of course, but would bring the diphoton excess in the 13 TeV data in greater tension with the 8 TeV null results.

4. When considering only the 13 TeV data, the Cms13 data does not share the Atlas13 preference for a 45 GeV width. I find that the “wide” interpretation of the resonance has a statistical significance in the combo13 data set which is approximately 0.5σ less likely than the “narrow” interpretation. The corresponding likelihood ratio shows no preference for either width. Thus, while the theoretical challenge of a wide resonance may be appealing, the data in no way requires any new physics explanation to have the unusually large width of Γ ∼ 45 GeV.

5. Combining the 13 TeV data with the 8 TeV, I find that gluon-initiated mediators are preferred, due to having the largest ratio of relevant p.d.f.s. In particular, the combination of all six data sets for a gluon-initiated narrow resonance has the same statistical preference for a signal as the Combo13 data alone does, though the best-fit cross section decreases slightly when the 8 TeV data is added (∼ 4.0σ for a ∼ 4 fb signal). In the narrow width assumption, heavy quark-initiated mediators have slightly smaller statistical preference, and a light-quark coupling has a fairly significant decrease in statistical preference, indicating a more serious conflict between the 13 and 8 TeV data.

6. Combining the 13 and 8 TeV data sets under the Γ = 45 GeV spin-0 model increases the statistical preference for signal as compared to the Combo13 result, as the excess can be more easily absorbed by the background model here. Combining all the data sets in this way results in a ∼ 3.5σ preference for a ∼ 10 fb signal (a 0.5σ increase over the Combo13 wide-resonance fit), with a likelihood ratio of ∼ 20 rejecting the narrow interpretation. Again, these statistical preferences are relatively small, thus theorists are free to explore the options, but should keep in mind that the experimental results are inconclusive.

The conclusions of this paper are perhaps not a surprise. There is clear tension between the Atlas13 and Cms13 results, as well as with the non-observation in 8 TeV data. The question of the width is especially puzzling; but further slicing of the data, as I have demonstrated, leads to somewhat conflicting results which do not have a clear statistical preference towards any one solution. I note that if the ATLAS excess is indeed an upward fluctuation from a signal which is more in line with the Cms13 value, then perhaps this could also give a spurious signal of large width. However, the true answers will only come with more data, though I note that, if the signal is indeed real, but on the order of 4 fb, then we may need 10-20 fb−1 for a single experiment to have 5σ discovery.

Some theorists have also hypothesized that this is really a quad-photon resonance with pairs of photons so close to each other that they register as single photons in the detectors.

Despite the superficial similarities of a spin-0 750 GeV particle to a Higgs boson, the resonance is very un-Higgs like.  For example, the primary decay of the Higgs boson is to b quark pairs, even though the diphoton channel is easier to see.  And, pairs of b quarks with 371 GeV of momentum (plus 4 GeV or so of rest mass) would be hard to miss.

Lubos who is a bit generous about fitting the data to numbers because he thinks this is probably real (he gives it a 50% chance of being real), also asks his readers to:

Recall that the ATLAS diphoton graph also shows an excess near 1.6TeV, close to two times 750GeV, and 375GeV is just a bit higher than twice the top quark mass, 173GeV.

I'm not as impressed with "almost" twice the mass, particularly when the 750 GeV v. 375 GeV pairing seems to be exact (although he also points to a possible 340 GeV mass for the lower bump). Twice the top quark mass is about 346 GeV, and twice that is about 692 GeV which is pretty much impossible to reconcile with 750 GeV unless you have a composite particle with some a lot of strong force binding energy to make toponium and very little to go further and make a toponium molecule or top tetraquark at 750 GeV that in turn almost instantly annihilates into photons.

But, of course, if you had a top quark-top antiquark composite particle, you ought to be seeing decays predominantly to pairs of b quarks and not to photons and Z bosons the way you do when pairs to top quarks that aren't bound to each other in hadrons are product.  To get those decays you'd need toponium to experience a matter-antimatter annihilation to photons before the constituent top quarks could experience weak force decay.  And, you'd probably want a process that produces the toponium from extremely high energy gluon fusion or something like that.  (Glueball annihilation is also naively attractive, but the predicted glue ball masses aren't anywhere near a 750 GeV resonance; they're much too light.)

The diphoton channel at that energy level doesn't have a lot of potential background noise, so even a pretty modest number of diphoton detections at that energy scale could be significant.

But, there are hundreds of papers, rather than just a few leading ones, because a resonance at this mass, with the characteristics it has and the lack of strong signals in other channels at the same energy level, is not very well motivated in any of the leading extension of the Standard Model of particle physics.  Also, the different data sets used to infer its existence are in some tension with each other.

For the most part, models that can accommodate a particle that decays to a 750 GeV diphoton resonance while having few other decay modes, require the existence of whole classes of other new particles to go with it (even if it is composite, rather than fundamental).  This gives rise to a very baroque new beyond the Standard Model theory.

For that reason, despite the notability of the bump statistically, my money is on this turning out to be a statistical fluke or systemic experimental error, rather than an actual new particle.

We'll learn if this prediction is right or not within a year or two, depending on how many more weasel, baguettes and other mishaps interfere with the LHC experimental schedule.

Did Human Female Pelvis Evolution Create Another Biological Clock?

The obstetrical dilemma hypothesis states that the human female pelvis represents a compromise between designs most suitable for childbirth and bipedal locomotion, respectively. This hypothesis has been challenged recently on biomechanical, metabolic, and biocultural grounds. Here we provide evidence for the pelvis’ developmental adaptation to the problem of birthing large-headed/large-bodied babies. 

We show that the female pelvis reaches its obstetrically most adequate morphology around the time of maximum fertility but later reverts to a mode of development similar to that of males, which significantly reduces the dimensions of the birth canal. These developmental changes are likely mediated by hormonal changes during puberty and menopause, indicating “on-demand” adjustment of pelvic shape to the needs of childbirth.

Via John Hawks.

Everyone know that women can only have children from puberty to menopause, and most people who have lived in the social world of college students know that female fertility declines markedly with age before menopause.  All of this, however, is basically directly hormonal and biochemical, not mechanical and morphological according to hormonal cues.

The new paper suggests that shifts in women's hips over their life cycle provides an independent biological clock that influences fertility and provides a biological bias towards having children in your 20s, rather than your 30s or later.  Of course, medically safe C-sections can now bypass the limits of the birth canal on safe births later in life.  But, this study ought to give pause to women who think that vaginal births for mothers of advanced maternal age are desirable because they are more "natural."

The issue of large-headed/large-bodies babies is a big one because many evolutionary anthropologists see large headed babies as a critical piece of evolution that has facilitated higher IQ in modern humans than in other primates.  And, it is widely accepted that higher IQ is a key factor in modern human selective fitness.

Given the ongoing relevance of IQ and the existence of safe C-sections, is it conceivable that we could evolve to a state where safe vaginal births are no longer possible because selection for high IQ leads to selection for large headed babies and hip size is not longer a meaningful constraint on that tendency?

This paper is also a welcome reminder that genetically driven phenotypes are not necessarily an all or nothing thing.  People's bodies change over their lifespans and our genes are clever enough to adapt one way at one age and another at a later age for maximum selective fitness.

Planet Nine Lacks A Good Origin Story

While a variety of investigators have been hot on the trail of determine where Planet Nine might be and what characteristics it might have, all of the origin stories for it are low probability ones.

Dilution Or Selection?

A new paper from Nature focuses on 51 ancient genomes from the Upper Paleolithic.

One notable observation is that Neanderthal admixture falls from 3%-6% in the early Upper Paleolithic to current levels of about 2%. This is attributed to selection, although dilution with less admixed populations could produce the same top line result. (Oase1 is an outlier at 10% from 40kya).

The paper's analysis suggests also that most Neanderthal admixture is quite old (long before cohabitation of Europe) and decayed slowly and steadily through slight natural selection, presumably in West Asia or SW Asia, rather than Europe. Indeed, the model is consistent with zero admixture of modern humans and Neanderthals in Europe itself.

Eurogenes captures many observations from the comments.

Broad brush, modern populations are really only in continuity with historic populations in Europe back to the Epipaleolithic era ca. 14,000 years ago when Europe's population was replaced following the Last Glacial Maximum when the Western Hunter Gatherer (WGH) autosomal population starts to gel.  Earlier individuals loosely cluster around MA1 from 24,000 years ago with one individual from ca. 19,000 years ago looking like a transitional figure.

This is one Epipaleolithic individual from Northern Italy ca. 14,000 year ago with Y-DNA R1b.  There are stronger Asia affinities in European individuals than would be expected for most of the Upper Paleolithic.

The picture form uniparental ancient DNA until now has been one of a very narrow, homogeneous gene pool with a small effective population size.  To the extent that this is true, it is a post-LGM phenomena as the ancient autosomal DNA over the tens of thousands of years and thousands of miles spanned by the sample shows only fairly loose affinity.

Two out of 21 pre-LGM samples are mtDNA-M (now found almost exclusively in East Eurasia).  Of 13 pre-LGM Y-DNA samples, three of C (now found almost exclusively in East Eurasia) and four are haplogroups that precede the East-West divide in Y-DNA haplogroups.