Monday, November 25, 2019

Hungarian Scientists Almost Surely Didn't Discover A Fifth Force

Scientists at the Institute for Nuclear Research at the Hungarian Academy of Sciences (Atomki) have posted findings showing what could be an example of that fifth force at work. 
The scientists were closely watching how an excited helium atom emitted light as it decayed. The particles split at an unusual angle -- 115 degrees -- which couldn't be explained by known physics. 
The study's lead scientist, Attila Krasznahorkay, told CNN that this was the second time his team had detected a new particle, which they call X17, because they calculated its mass at 17 megaelectronvolts. 
"X17 could be a particle, which connects our visible world with the dark matter," he said in an email.
From CNN (previous papers by the same group are linked to in the story with hyperlinks).

The odds are at least 98% that Hungarian scientists have made some sort of experimental error and have not discovered a fifth force (approximately the precision with which non-Standard Model physics are typically ruled out in broad ranging searches for "new physics" that aren't specifically predicted by a particular hypothesis of interest).

Why? 

Because there are a great many experiments that could have detected the 17 MeV mass particle that they claim to have seen (e.g. LEC, Tevatron, LHCb, ATLAS, CMS, Jefferson Labs, etc.) and none of the other experiments have replicated this result. ATLAS and CMS are sensitive to new physics particles up to about 1,000,000,000 MeV of mass. The two experiments at the Tevatron collider were sensitive to particles up to about 200,000 MeV of mass. The LEC was sensitive to particles up to about 100,000 MeV of mass. Particles with masses on the order of 17 MeV have been possible to observe in high energy physics experiments since the 1960s, if not earlier, and nobody has claimed to see them, until now.

More generally, myriad other high energy physics calculations would be affected by such a fifth force but are adequately explained by the plain old three forces of the Standard Model (also ignoring gravity).

17 MeV is about 34 times the mass of an electron, a muon is about 6 times as massive as 17 MeV, a pion (the lightest particle made out of quarks, which never appear in isolation in the real world) is about 8 times as massive as 17 MeV, and a proton or neutron is about 54 times as massive as 17 MeV. Neutrinos are on the order of a million or more times less massive than 17 MeV.

Particles such as this hypothetical particle, which purportedly have effects which can be seen electromagnetically (such as interactions involving the emission of light as claimed in this article), are particularly easy to see experimentally, because experimental electromagnetic measurements are among the most precise of all kinds of scientific measurements. The polarization and energies of single photons can be measured with modern physics instrumentation.

17 MeV is also a poor fit to most astronomy data related to hypothetical dark matter particle candidates based upon the inferred mean velocity of dark matter particle candidates in thermal freeze out scenarios, which tend to favor "warm dark matter" candidates on the order of 10,000 times less massive than 17 MeV.

Also, while a helium atom may seen pretty simple (usually two protons and two neutrons), this atom is close to the boundary of what it is possible to calculate from first principles from the Standard Model of Physics, and "hadronic matter" (i.e. particles made up of bound compound particles made of quarks), which is described with a combination of the strong force described by quantum chromodynamics (QCD), the electromagnetic force described by quantum electrodynamics (QED), and the Standard Model physics of the weak force, are exceedingly challenging to model mathematically from first principles. Almost all such calculations, in practice, are done using numerical approximations that each have their flaws and are least reliable in the low energy regimes (i.e. for masses and energies on the order of 2 GeV or so, plus or minus, with a helium atom having a mass of approximately 4 GeV) in which QCD calculations become "non-perturbative" (which basically means highly non-linear).

How else can you tell?

Any genuinely plausible experimental anomaly routinely results in hundreds of research papers attempting to explain this phenomena written by physicists all over the world, in a matter of weeks. This paper has generated no such academic interest, effectively illustrating an implicit form of negative peer review. If the claims of a fifth force held water, the physics pre-print depositor arXiv would be full of papers trying to explain this anomaly and it isn't.

Friday, November 22, 2019

Why Do Some LSB Dwarf Galaxies Have Lots Of Dark Matter While Some Seemingly Have None?

The paper does not consider whether the MOND external field effect (EFF) can adequately explain the departure from the mass discrepancy-acceleration relation that MOND codifies in the form of a phenomenological toy model gravity modification.
We use a sample of galaxies with high-quality rotation curves to assess the role of the luminous component ("baryons") in the dwarf galaxy rotation curve diversity problem. 
As in earlier work, we find that the shape of the rotation curve correlates with baryonic surface density; high surface density galaxies have rapidly-rising rotation curves consistent with cuspy cold dark matter halos, slowly-rising rotation curves (characteristic of galaxies with inner mass deficits or "cores") occur only in low surface density galaxies. 
The correlation, however, seems too weak in the dwarf galaxy regime to be the main driver of the diversity. In particular, the observed dwarf galaxy sample includes "cuspy" systems where baryons are unimportant in the inner regions and "cored" galaxies where baryons actually dominate the inner mass budget. 
These features are important diagnostics of the viability of various scenarios proposed to explain the diversity, such as (i) baryonic inflows and outflows; (ii) dark matter self-interactions (SIDM); (iii) variations in the baryonic acceleration through the "mass discrepancy-acceleration relation" (MDAR); or (iv) non-circular motions in gaseous discs. A reanalysis of existing data shows that MDAR does not hold in the inner regions of dwarf galaxies and thus cannot explain the diversity.
Together with analytical modeling and cosmological hydrodynamical simulations, our analysis shows that each of the remaining scenarios has promising features, but none seems to fully account for the observed diversity. The origin of the dwarf galaxy rotation curve diversity and its relation to the small structure of cold dark matter remains an open issue.
Isabel M.E. Santos-Santos, et al., "Baryonic clues to the puzzling diversity of dwarf galaxy rotation curves" (November 20, 2019) (submitted to MNRAS).

The conclusion in the body text states:
SUMMARY AND CONCLUSIONS

Dwarf galaxy rotation curves are challenging to reproduce in the standard Lambda Cold Dark Matter (LCDM) cosmogony. In some galaxies, rotation speeds rise rapidly to their maximum value, consistent with the circular velocity curves expected of cuspy LCDM halos. In others, however, rotation speeds rise more slowly, revealing large “inner mass deficits” or “cores” when compared with LCDM halos (e.g., de Blok 2010). This diversity is unexpected in LCDM, where, in the absence of modifications by baryons, circular velocity curves are expected to be simple, self-similar functions of the total halo mass (Navarro et al. 1996b, 1997; Oman et al. 2015). We examine in this paper the viability of different scenarios proposed to explain the diversity, and, in particular, the apparent presence of both cusps and cores in dwarfs.
 
In one scenario the diversity is caused by variations in the baryonic contribution to the acceleration in the inner regions, perhaps linked to rotation velocities through the “mass discrepancy acceleration relation” (MDAR; McGaugh et al. 2016). In agreement with previous work, we show here that the inner regions of many dwarf galaxies deviate from such relation, especially those where the evidence for “cores” is most compelling. We conclude that the MDAR does not hold in the inner regions of low-mass galaxies and, therefore, it cannot be responsible for the observed diversity. 
A second scenario (BICC; “baryon-induced cores/cusps”) envisions the diversity as caused by the effect of baryonic inflows and outflows during the formation of the galaxy, which may rearrange the inner dark matter profiles: cores are created by baryonic blowouts but cusps can be recreated by further baryonic infall (see; e.g., Navarro et al. 1996a; Pontzen & Governato 2012; Di Cintio et al. 2014a; Tollet et al. 2016; Ben´ıtez-Llambay et al. 2019). 
A third scenario (SIDM) argues that dark matter self-interactions may reduce the central DM densities relative to CDM, creating cores. As in BICC, cusps may be re-formed in galaxies where baryons are gravitationally important enough to deepen substantially the central potential (see, e.g., Tulin & Yu 2018, for a recent review). 
We have analyzed cosmological simulations of these two scenarios and find that, although they both show promise explaining systems with cores, neither reproduces the observed diversity in full detail. Indeed, both scenarios have difficulty reproducing an intriguing feature of the observed diversity, namely the existence of galaxies with fast-rising rotation curves where the gravitational effects of baryons in the inner regions is unimportant. They also face difficulty explaining slowly-rising rotation curves where baryons actually dominate in the inner regions, which are also present in the observational sample we analyze. 
We argue that these issues present a difficult problem for any scenario where most halos are expected to develop a sizable core and where baryons are supposed to be responsible for the observed diversity. This is especially so because the relation between baryon surface density and rotation curve shape is quite weak in the dwarf galaxy regime, and thus unlikely to drive the diversity. We emphasize that, strictly speaking, this conclusion applies only to the particular implementations of BICC and SIDM we have tested here. These are by no means the only possible realizations of these scenarios, and it is definitely possible that further refinements may lead to improvements in their accounting of the rotation curve diversity. 
Our conclusions regarding SIDM may seem at odds with recent work that reports good agreement between SIDM predictions and dwarf galaxy rotation curves (see; e.g., the recent preprint of Kaplinghat et al. 2019, which appeared as we were readying this paper for submission, and references therein). That work, however, was meant to address whether observed rotation curves can be reproduced by adjusting the SIDM halo parameters freely in the fitting procedure, with promising results. Our analysis, on the other hand, explores whether the observed galaxies, if placed in average (random) SIDM halos, would exhibit the observed diversity. Our results do show, in agreement with earlier work, that SIDM leads to a wide distribution of rotation curve shapes. However they also highlight the fact that outliers, be they large cores or cuspy systems, are not readily accounted for in this scenario, an issue that was also raised by Creasey et al. (2017). Whether this is a critical flaw of the SIDM scenario, or just signals the need for further elaboration, is still unclear. 
We end by noting that the rather peculiar relation between inner baryon dominance and rotation curve shapes could be naturally explained if non-circular motions were a driving cause of the diversity. For this scenario to succeed, however, it would need to explain why such motions affect solely low surface brightness galaxies, the systems where the evidence for “cores” is most compelling. Further progress in this regard would require a detailed reanalysis of the data to uncover evidence for non-circular motions, and a clear elaboration of the reason why non-circular motions do not affect massive, high surface brightness galaxies. Until then, we would argue that the dwarf galaxy rotation curve diversity problem remains, for the time being, open.

All Top Quark Mass Measurements And Some Notable Predictions For It Summarized

A Summary Of Top Quark Mass Measurements
Direct measurement of the top quark mass 
ATLAS: lepton+jets events at 8 TeV (20.2 fb−1 ). ... 172.69 ± 0.48 GeV, with a relative uncertainty of 0.28%. ...
CMS: dilepton events at 13 TeV (35.9 fb−1 ). ... 172.33 ± 0.14 (stat) +0.66 −0.72 (syst) GeV, with a total relative uncertainty of approximately 0.42%. ...
CMS: all-jets events at 13 TeV (35.9 fb−1 ). ... 172.26 ± 0.61 GeV, with a relative uncertainty of 0.36%. ...
ATLAS: lepton+jets with an additional soft µ at 13 TeV (36.1 fb−1 ). ... 174.48 ± 0.40 (stat) ± 0.67 (syst) GeV, with a total relative uncertainty of 0.45%. ...
Indirect determination of the top quark mass 
ATLAS: inclusive tt cross section in the eµ channel at 13 TeV (36.1 fb−1 ). ... 173.1 + 2.0 − 2.1 GeV. ...
ATLAS: differential cross section for lepton+jets tt+1jet events at 8 TeV (20.2 fb−1 ). ... 171.1 ± 0.4 (stat) ± 0.9 (syst) +0.7 −0.3 (theo) GeV [pole mass]. ...
CMS: triple-differential cross section in dilepton events at 13 TeV (35.9 fb−1 ). ... 170.5 ± 0.8 GeV [pole mass]. ... 
CMS: invariant jet mass distribution for boosted jets in lepton+jets events at 13 TeV (35.9 fb−1 ). ... 172.56 ± 2.47 GeV. ...
CMS: running of the top quark mass in eµ events at 13 TeV (35.9 fb−1 ). ... The observed evolution of the mt(µk) values agrees with the prediction from renormalization group equations at 1- loop precision within 1.1 standard deviations. The no-running hypothesis is excluded at 95% confidence level.
Abstract
The ATLAS and CMS Collaborations have performed a variety of measurements of the top quark mass, taking advantage of the abundant production of top quarks at the LHC. The most recent measurements are reported here, based on data collected at 8 and 13 TeV, with particular emphasis on the distinction between the so-called "direct" measurements and the "indirect" evaluations obtained from cross sections and differential cross sections.
Andrea Castro (on behalf of the ATLAS and CMS Collaborations), "Top Quark Mass Measurements in ATLAS and CMS" (November 21, 2019).

The final combined value from the two Tevatron experiments which were the first to measure the top quark mass was 174.30 ± 0.35 ± 0.54 GeV.

The Particle Data Group entity for this is here, but not as up to date. The latest direct measurement average from the PDG is 172.9 ± 0.4 GeV. The latest indirect measurement average from PDG is 173.1 ± 0.9 GeV. The weighted average of those two measurements was 172.96 GeV.

Combining The Results For A New World Average

To recap, the nine independent measurements at Tevatron and the LHC combined to date are:

172.69 ± 0.48 GeV
172.33 ± 0.14 (stat) +0.66 −0.72 (syst) GeV
172.26 ± 0.61 GeV
174.48 ± 0.40 (stat) ± 0.67 (syst) GeV
173.1 + 2.0 − 2.1 GeV
171.1 ± 0.4 (stat) ± 0.9 (syst) +0.7 −0.3 (theo) GeV
170.5 ± 0.8 GeV 
172.56 ± 2.47 GeV
174.30 ± 0.35 ± 0.54 GeV

Feel free to calculate an error weighted world average at your leisure (which I would if I had time). 

Step One

First combine the errors for each measurement by taking the square root of the sum of the squares of the errors (and the arithmetic average where upper and lower bound errors differ before combining different types of error). This gives you this (with extreme values in each category noted). 

LHC Results (likely to have some correlated errors)


172.69 ± 0.48 GeV (171.73 - 173.65 GeV) ATLAS direct
172.33 ± 0.70 GeV (170.93 - 173.73 GeV) CMS direct
172.26 ± 0.61 GeV (171.04 - 173.48 GeV) CMS direct
174.48 ± 0.78 GeV (172.92 - 176.04 GeV) ATLAS direct
173.1 ± 2.05 GeV (169 - 177.2 GeV) ATLAS indirect
171.1 ± 1.10 GeV (168.9 - 173.3 GeV) ATLAS indirect
170.5 ± 0.80 GeV (168.9 - 172.1 GeV) CMS indirect
172.56 ± 2.47 GeV (167.62 -177.5 GeV) CMS indirect

Tevatron Results


174.30 ± 0.64 GeV (173.02 -175.58 GeV)

Step Two

Then, use the inverse of the margin of error for each measurement to construct of weight for each measurement and take the weighted average. This give you:

172.65 GeV

Thus the latest experimental result from the LHC have pulled down the global average top quark mass by about 0.31 GeV from the value currently listed by the Particle Data Group.

Step Three

Then, calculate the margin of error of the weighted average from the inputs. A prior post somewhere at this blog explains how to do with simplifying assumptions. 

But, to really do it rigorously, you have to consider the fact that the systemic and theoretical errors are not fully independent of each other, particularly for results that are all from LHC (which tends to make the total combined margin of error greater), and that historically, in this kind of experiment, actual errors have had fatter tails than a Gaussian (i.e. "normal") distribution and are distributed in something closer to a student t-test distribution with different parameters established by the historical data, which also tends to increase the total combined margin of error. The combined error should be a little lower than, but fairly close in magnitude to, the lowest margin of error of any of the individual entries, unless there is very wide scatter of precise measurements, in which case the combined error should be higher than the lowest margin of error of the individual entries, because this pattern implies that one or more of the margins of error is underestimated.

I suspect that the combined margin of error is on the order of 0.35 GeV to 0.45 GeV. Using the higher figure to account for issues like correlated errors and non-Gaussian errors, the two sigma range for the top quark mass given current data is 171.75 GeV to 173.55 GeV.

Given comparison of the two sigma bands for each result and giving slightly more importance to the Tevatron value as it is more independent than the other values, I suspect that the true value of the top quark pole mass is probably between 172.92 GeV and 173.3 GeV, which favors the higher end of combined two sigma range.

Theoretical Comparison Points (Highly Speculative)

Other reference points from theory include the following conjectures, none of which is widely accepted among physicists, but is innocent enough to compare to the experimental results.  The world average is at the low end of these predictions, but the first two are consistent to within two sigma with the current world average, while the third theoretical number is not quite consistent with the world average including all measurements at two sigma.

The Extended Koide's Rule Estimate

An extended Koide's rule estimate of the top quark mass using only the electron and muon masses as inputs, predicted a top quark mass of 173.263947 ± 0.000006 GeV. This would be 173.26 GeV to the greatest precision that would be non spurious to compare to current experimental results. This is probably within 1.74 sigma of the current world average and also within the preferred region I identify above. 

If you read my prior posts about the extended Koide's rule, there is good reason to think that this value should receive a second order correction which is a small downward adjustment of this value. This is because it does not reflect top quark to down quark transition which are rare but not impossible. This rule as a whole should also be given something less than full confidence, because both the charm quark and up quark values estimated in this fashion are quite far from the experimentally measured values of these quarks, so it clearly needs some adjustment to accurately reflect reality and is only a first order approximation of the fermion mass matrix. This suggests that a corrected extended Koide's rule would need a roughly 151 MeV downward adjustment to the top quark mass.

The Higgs Vacuum Expectation Value Based (LP&C) Estimates

* The weak version of the LP & C hypothesis is probably true.

The sum of the squares of the pole masses of the Standard Model fundamental particles is almost precisely identical to the square of the vacuum expectation value of the Higgs field.

A fit comparing the two predicts a top quark mass of 173.1125 ± 0.0025 GeV. Most of the uncertainty in this value is due to the uncertainty in the Higgs boson mass. This is 173.11 GeV to the greatest precision that would be non spurious to compare to current experimental results. This is probably within 1.31 sigma of the current world average and also right in the middle of the preferred region I identify above based on harmonizing the two sigma ranges of the nine available mass measurements.

The boson side is also consistent with the weak version of this hypothesis at a roughly 1.3 sigma level.

I strongly suspect that this relationship is a true and accurate law of physics and that the top quark, as a result, has a true pole mass of 173.11 GeV.

* The strong version of the LP & C hypothesis is probably false.

The value of the top quark mass necessary to make the sum of the squares of the fermion masses equal to the sum of the square of the boson masses would with the combined amount equal to the square of the vacuum expectation value of the Higgs field is 174.974 GeV (with less than 0.0005 GeV of uncertainty). This is 174.97 GeV to the greatest precision that would be non spurious to compare to current experimental results. This is probably 6.6 sigma from the current world average and is at least 5.1 sigma from the current world average. It is also more than 5.1 sigma from the PDG direct measurement world average. 

On the boson side, the strong version of the hypothesis would require a Higgs boson mass of 124.66 GeV, which is 5.3 sigma away from the current PDG value of 125.10 ± 0.14 GeV, which is also pretty much definitively ruled out by the experimental data.

Thus, the strong version of this hypothesis is ruled out by experimental data, at the more than five sigma level, for both fermions and for bosons.

This would most directly imply, without other new physics, a lack of perfect harmony between fundamental fermion pole masses and fundamental boson masses in the universe, even though they are very nearly balanced (in much the way that the pion is almost, but not quite, a Goldstone boson and is, instead, a pseudo-Goldstone), and there is a slight imbalance in favor of bosons in the universe, for reasons unknown.

To the extent that one thinks about this approximate balance of masses as being some sort of "supersymmetric" (in the less strict sense) balance in the universe between fermions and bosons, this broad sense supersymmetry is an approximate, rather than an exact, symmetry of the universe. This approximate symmetry may help explain why supersymmetry theories can provide informative and useful predictions despite the fact that there is no positive evidence for the existence of any of the new particles or other new physics predicted in supersymmetry theories.

Friday, November 15, 2019

Severe Sixty Year Drought Felled Neo-Assyrian Empire

A new paper, once again, explains the rise and fall of an empire by looking at shifts in climate that coincide with them. In this case, a severe sixty year drought destroyed the Neo-Assyrian Empire. As the abstract explains:
Northern Iraq was the political and economic center of the Neo-Assyrian Empire (c. 912 to 609 BCE)—the largest and most powerful empire of its time. After more than two centuries of regional dominance, the Neo-Assyrian state plummeted from its zenith (c. 670 BCE) to complete political collapse (c. 615 to 609 BCE). Earlier explanations for the Assyrian collapse focused on the roles of internal politico-economic conflicts, territorial overextension, and military defeat. Here, we present a high-resolution and precisely dated speleothem record of climate change from the Kuna Ba cave in northern Iraq, which suggests that the empire’s rise occurred during a two-centuries-long interval of anomalously wet climate in the context of the past 4000 years, while megadroughts during the early-mid seventh century BCE, as severe as recent droughts in the region but lasting for decades, triggered a decline in Assyria’s agrarian productivity and thus contributed to its eventual political and economic collapse.



Time counterintuitively flows from right to left in this figure. 
It is unusually wet during green years and arid in red ones.


Ashish Sinha, et al. "Role of climate in the rise and fall of the Neo-Assyrian Empire." 5(11) Science Advances (November 13, 2019): eaax6656 DOI: 10.1126/sciadv.aax6656 (open access). Supplemental materials with historic and geographic context are here.

The body text elaborates on the story summed up in the figure above:
The z score transformed values of the detrended record delineating the drier intervals are similar to the values observed during the ~1980–2007 period of our record, the latter coeval with the period of the largest reduction in cool-season precipitation over the northern Iraq and Syria during the past century. The interval between ~850 and 740 BCE emerged as one of the wettest periods of the past 4000 years . . .  representing ~15 to 30% increase in the cool-season precipitation amount (relative to 1980–2007 CE). . . . 
This peak wet period, termed here the Assyrian megapluvial, was embedded within nearly two centuries (~925–725 BCE) of pluvial conditions and is synchronous with the prominent phases of the Assyrian imperial expansion (c. 920–730 BCE) within the margin of dating errors of both proxy (~25 years, 1σ) and historical records (~1 year). The age errors associated with the events surrounding the rise and fall of the Assyrian Empire are known with annual and, for many events, at monthly chronological precision. 
The [years] between ~800 BCE and ~700 BCE mark the transition from peak pluvial to peak dry conditions.  . . . The interval between ~675–550 BCE . . . emerged as a ~125-year period of peak aridity, termed here the Assyrian megadrought, which is synchronous, within the margins of dating error, with the period of the Assyrian imperial collapse, c. 660–600 BCE. The severity of the Assyrian megadrought is comparable in magnitude to the post-1980 CE drought inferred from our speleothem record—an observation that provides critical context for both historical and modern droughts.
The paper also hints that climate may also be driving contemporary politics in the region, noting early on that:
The core of the Assyrian Empire encompassed a triangular region in northern Iraq defined by the capital cities of Assur in the south (modern Qal’at Sherqat), the seventh century BCE Assyrian capital of Nineveh (modern Mosul) in the north, and Arbela (modern Erbil) in the east.

Mediterranean cyclonic systems in this region provide the bulk of annual precipitation (~90 to 95%) during the cool season (November to April), ranging from 600 to 1000 mm in the north and west to ~200 to 300 mm or less in the south and east.

Today, much of the region that constituted Assyria’s heartland and its hinterland is situated within the high-yield rain-fed cereal agriculture zone lying above the 200- to 300-mm isohyets, referred as a “zone of uncertainty” because interannual variability is typically 40 to 60% and rain-fed cereal cultivation is risky and unsustainable. During years of anomalously high and low rainfall, this agriculturally marginal zone shifts southward and northward by several hundred kilometers, rendering nearly all ancient Assyria’s heartland both favorable for high-yield cereal cultivation and vulnerable to crop failures.

The latter was demonstrated during the severe drought episodes of 1999–2001 and 2007–2008 when cereal crop failures and widespread livestock death were pervasive across northern Syria and Iraq. These droughts, which were the most severe in the past 50 years, were marked by up to 60% reduction in cool-season rainfall over northern Iraq that exacerbated regional socioeconomic conditions already suffering from decades of political instability and unsustainable socioeconomic policies.

Tuesday, November 12, 2019

Ancient Roman DNA

At the forest level, the only slightly surprising quirk in a new (paywalled) survey of ancient Roman DNA in the journal Science released last Friday is that its second demographic transition is unclear and on the late side, but still in the Bronze Age. There are no samples from 1700 BCE to 700 BCE, so there simply isn't the data to resolve this transition in detail with direct evidence (although deeper analysis of, for example, linkage disequilibrium in early Iron Age steppe ancestry components might help resolve this question in later studies even without new data). This is something that may be due as much as anything to Rome being a backwater until the early Iron Age when it was really founded as the city that it is today. 





The Near Eastern component largely drops out of the the Roman gene pool after the Imperial Roman period, although this could be simply due to the peculiarities of which samples with particular biases data to which eras.


The new paper and its abstract are as follows (emphasis added):
Ancient Rome was the capital of an empire of ~70 million inhabitants, but little is known about the genetics of ancient Romans. Here we present 127 genomes from 29 archaeological sites in and around Rome, spanning the past 12,000 years. We observe two major prehistoric ancestry transitions: one with the introduction of farming and another prior to the Iron Age. By the founding of Rome, the genetic composition of the region approximated that of modern Mediterranean populations. During the Imperial period, Rome’s population received net immigration from the Near East, followed by an increase in genetic contributions from Europe. These ancestry shifts mirrored the geopolitical affiliations of Rome and were accompanied by marked inter-individual diversity, reflecting gene flow from across the Mediterranean, Europe, and North Africa.
Margaret L. Antonio, et al. "Ancient Rome: A genetic crossroads of Europe and the Mediterranean" 366 (6466) Science 708 (November 8, 2019). DOI: 10.1126/science.aay6826

Bernard's Blog has a post that gets past some of the paywall limitations.

Razib notes that Rome was something of a population sink which absorbed cosmopolitan influences but didn't necessarily spread them. He has more analysis in an earlier post that observes that "Modern Romans descend from Italian peasants, who were less impacted by the predations of the Goths and Byzantines, and had higher fertility than urban dwellers even in peaceful times" and also notes that Christianity may have helpfully reduced inbreeding and clan based social organization in Europe.

Eurogenes opens up two threads for discussions of the fine details. 

* His first post asks "What's the difference between ancient Romans and present-day Italians?" A question the new paper answers with "not much." 

* His second post is entitled: "Open analysis and discussion thread: Etruscans, Latins, Romans and others", the biggest upshot of which is that Etruscan ancient DNA differs surprisingly subtly from that of nearly contemporaneous Indo-European language speakers. This is arguably the most notably inference that can be drawn from the data including this new paper. Some notable comments from that thread (my emphasis in bold):





Romulus said...
It's really weird that the Iron Age Italians prefer Yamnaya over all these Beaker or CWC groups as a 2 way fit with Copper Age Italians.

It seems to imply that the Steppe group which brought M269 to Italy branched off before the group that led to the Lech Valley Beakers. Giving Italians a less diluted form of Steppe.

There were Copper Age Italian like groups (Hungarian Beaker) mixing with Yamnaya in the Carpathian Basin.

But what it probably is a reflection of is a migration of this Bronze Age Croatian like group represented by R437 bringing additional Steppe from the Balkans after the initial Beaker groups. The J2b Croatian had a lot of Steppe and R437 shows that on the PCA.
ǵenh said...
@ Davidski

That's right, David.

The Proto-Villanovan culture is a Late Bronze culture present throughout Italy from the Alps to eastern Sicily, which is considered Proto-Italic but not exclusively Italic. In the sense that almost all subsequent cultures of the Iron Age of Italy derive from Proto-Villanovan culture, both Iron Age Italic (Latin, Osco-Umbrians) and non-Italic cultures (Veneti, Etruscans). Especially in the past, even the Culture of Golasecca (which is typical of north-west Italy from which derive the Celts who speak a lepontic language) was believed to be derived from the Proto-Villanovan culture.

While the Villanovan culture is an Iron Age culture that is the first phase of the Etruscans, the beginning of the Etruscan civilization, according to what is now the most accepted Etruscan chronology by scholars.

The misunderstanding between the two names was born because the Villanovan culture associated to the Etruscans was the first to be discovered by archaeologists around the middle of the 1800s. When in the 1930s archeologists also discovered settlements of Protovillanovan culture, at first they thought that it was only an earlier phase of Villanovan culture. Only later they understood that the Protovillanovan culture was instead the previous phase of many other cultures present in Italy, including the Italic ones, but the name was never changed, and this has contributed to creating confusion.
Samuel Andrews said...
Romulus,
"It seems to imply that the Steppe group which brought M269 to Italy branched off before the group that led to the Lech Valley Beakers. Giving Italians a less diluted form of Steppe."

What I'm seeing, is Latins perfer Bell Beaker from Germany & Czech.

"There were Copper Age Italian like groups (Hungarian Beaker) mixing with Yamnaya in the Carpathian Basin."

R1b P312+ isn't from Yamnaya. It's from Corded Ware. A R1b L51+ has been found in Corded Ware. It's unlikely there were groups with mostly Yamnaya/Kurgan ancestry in Central Europe in the Bronze age. The groups who went to Italy were already probably under 50% Yamnaya.
Gaska said...
*ETRUSCANS-

1-They are practically identical to Latins (24-28% Yamnaya)
2-Descend from BBs (45-50%)
3-We have cases of Bbs in Parma with Iberian signal in its Autosomal DNA
4-Italian Chalcolithic has a strong Iberian signal-
5-Etruscans are a mixture of local Eneolithic + Balkans + BBS-
6-Very similar to the Iron Age Iberians and Northern Italians
7-They have more Balkan mix than Latins
8-Obviously they were NOT Africans or Anatolians, nor Levantines-
9-Its mitochondrial markers are typically western (WHG-EEF and Iberian)
10-Heirs of the Villanovan culture that comes from UrnField Culture
11-We only have a male marker and I think it comes from Illyria
12-They spoke a non-Indo-European language-

Also, keep in mind that Sam is an expert in declaring the end of the story without any reason to do so.

It is essential to know more information about the Bronze Age in Italy (we do not have a single sample yet) and more data on the uniparental markers of the Etruscans, because they are also direct descendants of the BBs and therefore the doubts about the language spoken by the BB culture still exist
Archi said...
[Quoting Gaska above] . . .

1. R475 is almost identical, yeah. When there are only three of them. R850 is also a sample.
2. thus it is possible to name any other percent and anybody else.
5. You can name any other combination. If you forget about R475.
6. And we can say that Very unsimilar to the Iron Age Iberians and Northern Italians
7. Can we say that they have not Balkan mix than Latins
8. We will forgot further, the main thing is not to turn to R475 (and R850)
9. They have typical mito for Europe and Anatolia
10. Villanova are not their culture.
11 This male marker is much closer to Nuragic Sardinia and without any steppe components, it was not there before the nuragas.
12. Nobody knows the language of which group they spoke, but definitely not Basque. He had the strongest connections with Lydia.
Andrzejewski said...
Can we claim then that Etruscans are basically almost identical to Italics, save for an extra layer of admixture stemming from migrants from the Balkan who were rich in EEF and must’ve spoken a farmer language? Is it from areas close to Lemnian? If so, would Etruscan be considered a Lengyel sourced language?

I would interject that Etruscan was indeed not Indo-European and also not Basque, although its associations with other attested non-Indo-European language of Europe like Lemnian is cryptic because non-Indo-European languages of the Mediterranean other than Etruscan, Basque and the Afro-Asiatic languages of the region (e.g. Phoenician, Maltese and Hebrew) are very poorly attested. Etruscan was still in living language in classical Rome at a stage when history and linguistics had finally started to cross over from myth and legend to serious scholarly pursuits with recognized experts. Classical Roman scholars were wrong about many things, and their work in this area can't easily be tested because Etruscan hasn't been fully deciphered, but they wouldn't have missed anything too obvious to someone who had access to the information available in the capital of the Roman Empire.




FrankN said...
Do I get this correctly? Some models, such as the original ones from the paper, and also those run by Matt, speak in favour of an Anatolian_BA (CHG-enhanced) element in the genesis of Etruscans and IA_Italics, while others seem to favour a BB descent instead. Could someone try to clarify this, possibly by treating each sample separately? E.g., "Italic" R1021, 7th cBC, is according to the SuppMats coming from a site half-way between Rome and Naples characterised by "Italic archaeological findings and Pelasgic walls, characteristic of the people of the Bronze Age Aegean" - IOW: We may be dealing with an outpost of Magna Graecia rather than a typical "Italic" assemblage.

Linguists have long been puzzled by Anatolian - ItaloCeltic isoglosses such as the passive marked by infixed -tu-. A parsimonious explanation could be that Italo-Celtic represents an originally Anatolian language (probably Luvic rather than Hittite-like) which entered during the MBA and was later overformed by some kind of Illyro-Germanic that came in with the Urnfield expansion.
As to Etruscan-HurroUrartean connections: A genetic relation isn't yet universally accepted, but seems to enjoy increasing support. From https://en.wikipedia.org/wiki/Alarodian_languages:

"The term "Alarodian languages" was revived by I.M. Diakonoff for the proposed language family that unites the Hurro-Urartian and Northeast Caucasian languages.(..)

The inclusion of Etruscan and the related Tyrsenian languages has also been proposed, first by Orel and Starostin in 1990, on the basis of sound correspondences.[13] Facchetti has argued that there is a "curious" set of isoglosses between Etruscan and Hurrian[14], while Pliev proposed instead that Etruscan had a Nakh substrate.[15] In 2006, Robertson developed the hypothesis for including Tyrsenian further by presenting reconstructions of common ancestral forms of the numerals, and proposed cases of apparent sound correspondences between Etruscan and Nakh, with discussion also of Hurro-Urartian, Lemnian and the various Dagestanian branches.[16]
".

Apparently, Gamkrelidze/Ivanov 1990 have stressed particular closeness between NE Caucasian and Etruscan. A Fournet, while sceptical about a HU-NEC genetic relation, speaks out in favour of Tyrrhenian-HU relatedness (see my comments to the previous post). Kozyrski e.a. 2015 (http://www.aiscience.org/journal/j3l) came up with a number of fresh Etruscan-NEC (&HU) isoglosses.

Last but not least, V.V. Ivanow "Comparative Notes on Hurro-Urartian, Northern Caucasian and Indo-European" glosses over various HU/NEC - Etruscan connections, e.g. as concerns the plural on -(a)r shared by HU, NEC and Etruscan, Etruscan eis-er/ais-e/ar vs. Hurr. e-en-za-a-ri "gods", HU *pur(r)a "slave, servant" also present in Etruscan (plus Latin puer "boy", w/o satisfying IE etymology), and the etymological relation between the Etruscan toponym Mantua and the Urartian Mantupa.

https://pies.ucla.edu/IESV/1/VVI_Horse.pdf

Last but not least, a couple of Austrian archeologists have related the Taurus (S. Anatolia) to the Tauern (E. Alps) massives (c.f. the Taurisci in IA N. Italy). Note in this context Etruscan tul, Chechen t'o "stone" [albeit the t<->r sound shift would require explaination].
FrankN said...
Correction to my previous post: I mistook the Taurisci, who actually settled around the Tauern massive in Austria, for the NE Italian Taurini, who lent there name to the city of Turin.
FrankN said...
Ric: "So what you are basically saying is that Italic and Celtic originated in Anatolia to try and make the Hurro-Urartian thing work...?"

Not quite. What I am saying that linguists have for long known about a specific closeness between Anatolian and Italo-Celtic, w.o. so far being able to explain the reason for this closeness. An EBA migration out of Anatolia into Italy would provide a sensible explanation.

Otherwise, ItaloCeltic also has a lot in common with Germanic (albeit some phylogenies, e.g. the one proposed by D. Ringe, group Germanic with Albanian, others have Germanic clustering with Balto-Slavic). In this sense, the terminology "originated in [Anatolia]" is probably misplaced. We should rather think in terms of admixture and overforming, as also happened with English (Latin overforming Insular Celtic, to be overformed by first W., than N. Germanic, and ultimately heavily absorbing Franco-Norman, which in itself was a Gaulish-Latin-Germanic hybrid).

IA Italy by ca. 500-400 BC, displayed a huge linguistic diversity, including
- several fairly differentiated Italic languages falling into three different families (Osco-Umbrian, Latin-Faliscan, Venetic [phonetically Italic, grammatically probably a distinct language/family in its own right]);

- Other IA, especially Celtic (Lepontic, possibly further Celtic language), Ancient Greek in S.Italy, plus possibly also Illyrian languages along the Adriatic coast;
- Non-IE languages such as Etruscan, Rhaetic, Semitic (Punic), possibly Ligurian, Paleosardinian, and maybe a couple more.

The Punic and Old Greek cases seem relatively clear, but otherwise this linguistic diversity is so far poorly understood. Even if we just focus on non-Greek IE languages: Their diversity is unlikely to have evolved from just a single introgression, e.g. Urnfield-related ca. 1.200 BC. One possibility would be that IE was already spoken in Italy since a long time, maybe EEF, or BB. Both scenarios are IMO unlikely: There is substantial linguistic evidence against EEF speaking IE, and the BB impact on Italy (aside from the questions on BB language thrown up in Iberia) was extremely limited, both archeologically and genetically.

As such, I think the explaination for Italy's linguistic diversity during the middle IA lies in a series of IE introgressions from the MBA onwards, which brought several already fairly differentiated IE languages there (interactction with non-IE substrate, and Etruscan/ Semitic superstrate, provided for further differentiation). One obvious source is Urnfied via the E. Alps, a second one would be the (Pre-Proto-)Illyrian-speaking Balkans, but in addition to those two, Anatolia also looks linguistically promising.
Samuel Andrews said...
I looked at the Imperial Roman samples. 48 samples are in G25 PCA These are my opinons......

41 of 48 are over 50% Middle Eastern. On average, they are 66% Middle Eastern.

Where in the Middle East did they come from????
Asia Minor=22
Syria=9
Levant=4
Mesopotamia=5
Samuel Andrews said...
These was real Middle Eastern admixture in Roman-era Italy not the kind the ancient Greeks had. Ancient Greeks had Western Anatolia, EEF-rich, IranN-low, Levant-low kind of Mid East admixture.

This new Mid East admix in Roman era Italy came from the "interior" Middle East not the Aegean/Western Anatolia.

Meaning, they weren't all majority AnatoliaBA-like. They had complex ancestry which had significant doses from all over the ancient Middle East: Anatolia, Levant, Caucasus, Iran.

Overall, Cyrpiots are the best modern references. Because Cypriots are mostly ANatolia-BA but also have significant recent Levant-BA and recent Mesoptamia like ancestry.
FrankN said...
I would for the time being suggest some caution as concerns the "Etruscan" samples. The locations in question may rather have been assigned to Etruscans on political than on linguistic grounds. After all, Rome was also an "Etruscan" city until they kicked out "Etruscan" Tarquinius Superbus in 509 BC. Let's wait for aDNA from Tuscany, where there (hopefully) is some more certainty that not only the political elite, but also commoners actually spoke Etrurian.

Otherwise, that HRV-IA I1331 sample has been found not too far away from the area of the IA Liburnians.
https://en.wikipedia.org/wiki/Liburnian_language:
"Following studies of the onomastics of the Roman province of Dalmatia, Géza Alföldy has suggested that the Liburni and Histri belonged to the Venetic language area.[4][5] In particular, some Liburnian anthroponyms show strong Venetic affinities, a few similar names and common roots, such as Vols-, Volt-, and Host- (< PIE *ghos-ti-, "stranger, guest, host"). Liburnian and Venetic names sometimes also share suffixes in common, such as -icus and -ocus.
(..)
Other toponymical and onomastic similarities have been found between Liburnia and other regions of both Illyria and Asia Minor, especially Lycia, Lydia, Caria, Pisidia, Isauria, Pamphylia, Lycaonia and Cilicia, as well as similarities in elements of social organization, such as matriarchy/ginecocracy (gynaikokratia) and the numerical organization of territory. These are also features of the wider Adriatic region, especially Etruria, Messapia and southern Italy.[10] (..)
The old toponym Liburnum in Liguria may also link the Liburnian name to the Etruscans,[12][13] as well as the proposed Tyrsenian language family.
 "

Right- that's the linguists' story, that to some extent matches, and to some extent not, what aDNA now starts to reveal. To grab the full story, we'll need lots of MLBA aDNA.

Rob: "Etruria was able to rise amidst all this because of it contacts with the Nuraghi, which were one of the few powers which were able to maintain their trans-Mediterranean contacts amidst the said collapses, via Cyprus. "
I don't think that is the full story. Etruria's rise also has to do with control of Italy's richest iron ore deposits, especially those on Elba (and in addition also sophisticated iron smithing and Welding craftsmanship). See for details
https://brunelleschi.imss.fi.it/itineraries/itinerary/MetallurgyTuscany.html