Monday, September 30, 2019

Why Does Rosh Hashanah Start When It Does?

In 2019, Rosh Hashanah began yesterday at sunset and ends tomorrow evening, roughly, but not exactly (as expected in a lunar Jewish calendar) at the time of the autumnal equinox.
Rosh Hashanah is not mentioned in the Torah, Judaism’s founding religious text, and appears under different names in the Bible. Though the holiday was likely well established by the sixth century B.C.E, the phrase “Rosh Hashanah” shows up for the first time in the Mishna, a Jewish code of law compiled in 200 C.E [that is the first major written product of Rabbinic Judaism].

The Hebrew calendar begins with the month of Nisan, but Rosh Hashanah occurs at the start of Tishrei, when God is said to have created the world. For this reason, Rosh Hashanah can be seen as the birthday of the world rather than New Year’s in the secular sense; still, it is on Rosh Hashanah that the number of the civil year increases. The Mishna described three other “new years” in the Jewish calendar in addition to Rosh Hashanah. Nisan 1 was used to resume the cycle of months and measure the duration of kings’ reigns. Elul 1 resembled the start of the modern fiscal year and determined the tithing of animals for charity or sacrifice. Shevat 15 calculated the age of fruit-bearing trees and is now celebrated as the minor holiday of Tu B’Shevat. 
According to tradition, God judges all creatures during the 10 Days of Awe between Rosh Hashanah and Yom Kippur, deciding whether they will live or die in the coming year. Jewish law teaches that God inscribes the names of the righteous in the “book of life” and condemns the wicked to death on Rosh Hashanah; people who fall between the two categories have until Yom Kippur to perform “teshuvah,” or repentance. As a result, observant Jews consider Rosh Hashanah and the days surrounding it a time for prayer, good deeds, reflecting on past mistakes and making amends with others.  
 From here


At the time these dates were established, the Jewish people subject to the people setting these dates lives in the Southern Levant with periods of "Babylonian exile" in Mesopotamia. The time period in question starts before Roman conquest and extends to a time period after it. The first written attestation of the date of Rosh Hashanah is after the diaspora begins (70 CE), but before either written historical accounts or genetic evidence suggests that there was mass migration of Jews to Europe.

In contrast, the Roman Empire's calendar that ultimately became the basis for the calendars of the Roman Catholic and Eastern Orthodox churches, which also served as the secular calendar of Europe after the fall of the western Roman Empire, started in the spring (which is why "December" the tenth month, is in the winter).

The Chinese lunar calendar also begins in the winter, typically in roughly January by the Roman calendar.

The Jewish lunisolar calendar developed multiple New Year's for different purposes. As Wikipedia explains:
The Jewish calendar has several distinct new years, used for different purposes. The use of multiple starting dates for a year is comparable to different starting dates for civil "calendar years", "tax or fiscal years", "academic years", and so on. The Mishnah (c. 200 CE) identifies four new-year dates: 
The 1st of Nisan is the new year for kings and festivals; the 1st of Elul is the new year for the cattle tithe... the 1st of Tishri is the new year for years, of the years of release and jubilee years, for the planting and for vegetables; and the 1st of Shevat is the new year for trees—so the school of Shammai; and the school of Hillel say: On the 15th thereof.
Two of these dates are especially prominent: 
* 1 Nisan is the ecclesiastical new year, i.e. the date from which months and festivals are counted. Thus Passover (which begins on 15 Nisan) is described in the Torah as falling "in the first month", while Rosh Hashana (which begins on 1 Tishrei) is described as falling "in the seventh month". Since Passover is required to be celebrated in the spring, it should fall around, and normally just after, the vernal (spring) equinox. If the twelfth full moon after the previous Passover is too early compared to the equinox, a 13th leap month is inserted near the end of the previous year before the new year is set to begin. According to normative Judaism, the verses in Exodus 12:1–2 require that the months be determined by a proper court with the necessary authority to sanctify the months. Hence the court, not the astronomy, has the final decision. 
* Nowadays, the day most commonly referred to as the "New Year" is 1 Tishrei (Rosh Hashanah, lit. "head of the year"), even though Tishrei is the seventh month of the ecclesiastical year. 1 Tishrei is the civil new year, and the date on which the year number advances. Tishrei marks the end of one agricultural year and the beginning of another, and thus 1 Tishrei is considered the new year for most agriculture-related commandments, including Shmita, Yovel, Maaser Rishon, Maaser Sheni, and Maaser Ani.
Thus, to some extent, the Jewish calendar starts in the spring like the Roman calendar used to, and to some extent it starts in the fall, although autumn in the Southern Levant or Mesopotamia (like each of the other seasons in this region) bears little resemblance in climate to autumn in Europe or in northern North America.

The typical timeline of Rosh Hashanah is also a bit early for the last pre-winter harvest in a Mediterranean climate, which is usually more like late October or early November.

One plausible possibility is that he migration of the "most important" of the New Year's of the Jewish calendar from the spring start described in the Torah to the fall beginning that became normative at least in the Rabbinic era, if not earlier, reflects the transition of the Hebrews from being herders, as they were according to their own tradition immediately prior to settling in the Levant, to farmers embedded in a larger urban society. But, there don't seem to be definitive answers to this question.

Sunday, September 29, 2019

Why Does Legendary History Cover The Time Period That It Does?

At some point, history starts to consist of reasonably reliable historical accounts of things that actually happened without fantastic or mythical elaboration, even if it isn't completely free of fantastical flourishes that never happened.

In the Hebrew Bible, Genesis and Exodus are predominantly legendary history, but as you progress in the timeline, the text gets more historical. This is roughy at the Bronze Age-Iron Age transition in the Levant.

In ancient Greek and Roman societies, legendary history, like the Illiad, takes place at the tale end of the Bronze Age and the same is true of much of Greek mythology, while texts get more historical when the "dark ages" following Bronze Age collapse have ended and you begin the Iron Age proper around 10th or 9th century BCE.

Persian and South Asian legendary history is mostly in a Bronze Age setting as well.

And, this is also true outside the Indo-European linguistic sphere, with the legendary history era in China also corresponding to the Bronze Age, for the most part.

There are genuine more historical accounts that date to the Bronze Age, particularly Hittite, Akkadian, Egyptian and Sumerian historical records that only really drift off into more legendary history in the Eneolithic a.k.a. Chalcolithic a.k.a. Copper Age, especially before the climate event ca. 2000 BCE that transformed Mesopotamian and Egyptian society.

Even "The Lord of the Rings" is set in a basically Bronze to Iron Age transition era.

Is the issue one of when writing became widespread enough to produce chronicles and not just entertaining myths? 

Is the issue one of what kind of story survives oral history with mythical elements making it more memorable (most legendary history purports to be a much later documentation of events that were contemporaneously remembered in the form of oral historical accounts, often in verse)? 

Is the issue that chronicles of older periods were made, but were made in mediums that did not survive catastrophic collapses of civilization during which they couldn't be recopied by scribes?

Writing capable of transcribing the full range of language, as opposed to mere book keeping and trademark symbols like the Harappan and Vinca script, was basically not invented almost anywhere until the Eneolithic era of that society or later, so it makes a certain amount of sense that we have far less legendary history from the Neolithic era or the Upper Paleolithic, by why wouldn't oral histories have survived in greater numbers from those eras?

Wednesday, September 25, 2019

Dark Matter Particle Parameter Constraints From Cross-Sections Of Interaction And SM Boson Decays

This is a cross-post of a couple of comments at the Physics Forums.

Meta Update (September 26, 2019): I kind of prefer the font below to the one I've been using for a while. Comments pro or con on whether I should change the default font in blogger if I can figure out how to do it are welcome.

Cross-Sections Of Interaction With What (And Self-Interacting Dark Matter Models)?

There are dozens of Dark Matter (DM) particle candidates.

And, of course, the answer also depends upon cross-sections of interaction with what (e.g. many self-interacting dark matter candidates have a cross-section of interaction of DM particles with other DM particles comparable to that of ordinary protons and neutrons with each other, but a tiny or non-existent cross-section of interaction with ordinary matter). The estimates of self-interaction cross-sections of DM with DM are based primarily upon observations of colliding galactic clusters such as the Bullet Cluster.

Experimental Exclusions For Dark Matter-Nucleon Cross-Sections

An easier and related question is what cross sections of interaction with ordinary matter nucleons are ruled out experimentally.

There are charts of cross-sections of interactions with nucleons (i.e. protons and neutrons) that have been excluded by a combination of multiple experiments. Where lines appear in the chart, cross-sections above those lines are ruled out by the experiment that the line is named after. The chart below is from a July 31, 2015 paper by the CMS collaboration. Greater nucleon cross-sections have been excluded in the meantime, but this was the chart that I could pull up most conveniently.

cmsdmsearch2014.jpg

This second chart from May of 2018 (via the Resonaances blog compiled from the sources linked therein) is more recent but excludes limits from the LHC such as those shown in the chart above (which are the strongest limits for lower mass dark matter particle candidates). The dotted blue line labeled "Z portal Cx=1" in the chart below is basically equivalent to the cross-section of interaction with nucleons of ordinary Standard Model neutrinos.

femtobarn (fb) is 10^-39 cm^2. An attobarn (ab) is 10^-42 cm^2. A zeptobarn (zb) is 10^-45 cm^2. A yoctobarn (yb) is 10^-48 cm^2.

WIMPsDirectDetection.png

The Combined Dark Matter-Nucleon Cross-Section Exclusions

Combining the charts, for Dark Matter Masses of 1-10 GeV as of 2015 LHC data, the exclusion for spin-independent interactions with spin=1 dark matter particles is roughly equal to the Z portal Cx=1 line and the exclusion for spin-independent interactions with spin=0 dark matter particles is roughly 1 zb at 1 GeV of dark matter particle mass and a slightly larger cross-section (10^-44 cm^2) at 10 GeV, gradually declining between the two points.

The reason that direct detection experiments like Xenon 1T are less powerful at excluding dark matter candidates at low masses is because distinguishing signals from neutrino flux backgrounds that are not precisely known becomes a challenge at those masses.

In general, cross sections of interaction of dark matter with nucleons is less than 1/1000th of the cross-section of interaction with neutrinos at most masses down to 8 GeV for almost all kinds of dark matter particles and down to 1 GeV for scalar (spin=0) dark matter particles that have spin independent interactions between dark matter particles and nucleons, but less restrictive for dark matter particles of under 8 GeV that do not have not spin-independent interactions or do not have spin=0.

Millicharged Dark Matter

Dark matter candidates with cross-sections of interaction with nucleons on the order of 1/1000th of the cross-section of interaction of neutrinos with nucleons are called "millicharged" dark matter particle candidates.

These are attractive candidates mostly because direct dark matter detection experiments do not rule them out.

There Is Not Credible Evidence Of Direct Dark Matter Detection

There is, in general, zero experimental evidence ever by any means that is confirmed by more that one experiment of any signal of dark matter particles, and there is no discovery level (five standard deviations from a null hypothesis) of a signal of dark matter particles. There were some isolated and inconsistent signals of dark matter-nucleon interactions at low statistical significance in some early direct dark matter detection experiments, but all of the signals have been conclusively ruled out by multiple other experiments of the same type with higher capacity to see such signals.

All of this is complicated by a need to explain the close correlation between inferred dark matter distributions and the distribution of ordinary (a.k.a. baryonic) matter in a galaxy or galactic cluster, which is strongly suggestive of some cross-section of interaction between dark matter particles and ordinary matter that is materially stronger than the neutrino-nucleon cross-section of interaction combined with the purely gravitational interaction of dark matter with ordinary matter assuming standard weak field general relativity. This is one reason among several that the current trend in dark matter particle proposals is to focus on "light" (i.e. less than 1 GeV) mass dark matter particle candidates such as "warm dark matter", "sterile neutrinos", and "axion-like particles."

WIMP Dark Matter

The earliest main candidate for dark matter was the WIMP (weakly interacting massive particles, mostly often the lightest supersymmetric particle), which was believed to have a particle mass between 10 GeV and 1000 GeV or so. In the strict sense of the term, a WIMP was weakly interacting in the technical sense of interacting only via the weak nuclear force (basically via Z boson interactions) with a cross-section of interaction equal to the neutrino with nucleons (since this was a property of electromagnetically neutral supersymmetric particles), and this narrow sense WIMP has been pretty much ruled out. But, in the broader sense, the "weakly interacting" aspect of a WIMP is defined in a more colloquial sense as very weak but non-zero, in which case it is ill defined and could have a smaller cross-section of interaction with a nucleon than a neutrino, in which case it is not ruled out by direct detection experiments.

Supersymmetric WIMPs are pretty much ruled out by direct dark matter detection experiments. There are really no widely considered theories devised for any reason, but to specifically fit direct dark matter detection experiments, that predict that millicharged WIMPs should exist.

Sterile Neutrino Dark Mattter

Sterile neutrinos have no tree level interactions with other matter at all, but have a tiny interaction indirectly because a true "sterile neutrino" oscillates into an ordinary active neutrino at some low probability and approximately speaking, that low probability times the cross-section of interaction of an active neutrino with a nucleon is an effective cross-section of interaction with nucleons for a sterile neutrinos. (I distinguish a "true sterile neutrino", because sometimes the term "sterile neutrino" is used less discriminatingly as a dark matter particle with no cross section of interaction via the strong, electromagnetic or weak forces even if it does not oscillate with active neutrinos in some way.)

True sterile neutrino dark matter is favored most strongly with masses on the order of 1 eV (based upon the "reactor anomaly" which is a subject for another post), and almost always significantly less than 1 keV. So, experiments are not sufficiently sensitive to detect the predicted cross-section of interaction that a sterile neutrino should have with ordinary matter.

Thermal Freeze Out Dark Matter And Implications For Cross-Sections Of Interaction

Most (but certainly not all) dark matter particle candidates are presumed to have "frozen out" after the Big Bang at a characteristic temperature that relates dark matter particle mass and dark matter particle mean velocity. In those models "colder" dark matter particles (i.e. dark matter particles with lower mean velocity) are more massive, while "warmer" dark matter particles (i.e. dark matter particles with higher mean velocity) are less massive.

Normally "cold dark matter" in the strict sense, when referring to thermal freeze out dark matter particles, refers to particles 1 GeV or more, "warm dark matter" involved particles in the 1 keV mass order of magnitude, and "hot dark matter" involves particles with relativistic mean velocities that typically have masses comparable to neutrinos. But, the mass-mean velocity relationship breaks down for dark matter particles that are not generated by thermal freeze out.

I bring up this distinction because galaxy dynamics and the amount of structure in the universe largely rule out both colder dark matter particles, and hot dark matter particles, as serious dark matter candidates. Instead, thermal freeze out models taken together with galaxy dynamics and large scale structure tend to favor "warm dark matter" with masses on the order of a keV, and that small mass does not have a terribly tightly constrained cross-section of interaction with ordinary matter since it is so hard to distinguish between the neutrino background and the dark matter signal.

Non-Thermal Freeze Out Models

Two kinds of dark matter particles are that are good examples of models that are not thermal freeze out models. These are sterile neutrino models and axion-like particle models.

Primordial Black Hole Dark Matter

Primordial black hole dark matter candidates (i.e. black holes with an initial mass of less than the roughly three stellar masses at which they form naturally in non-Big Bang conditions), which are ruled out except in a narrow mass range as the primary component of dark matter (roughly big asteroid masses), of course, have extremely high (basically 100%) cross-sections of interaction with nucleons, but there are far fewer of them out there since they would be much more massive than other dark matter particle candidates.

If dark matter is too "hot" (i.e. relativistic speeds and typically neutrino scale masses), you get too little structure (e.g. no galaxy formation). But, if dark matter is too "cold", you get too much structure relative to what is observed (e.g. far more tiny galaxies than we observe, and far more substructures within normal sized galaxies than we observe). Dark matter particles have to be "warmish" to produce the right amount of structure.

W Boson and Z Boson Decay Constraints

Because of the way that the weak force operates, any particle that interacts via the weak force and has a rest mass of less than 45 GeV, give or take, must be produced in the decay of W and Z bosons that carry the weak force. Basically, in quantum physics everything that is possible must happen with some fixed probability. This is why we know, for example, that there can be only three kinds of "active" neutrinos (i.e. neutrinos that interact via the weak force) with masses of 45 GeV or less.

This is a huge gap considering that the heaviest active neutrino is directly constrained by a recent experiment to have a mass of only a little more than 1 eV (with cosmology and neutrino oscillation data suggesting masses even lower of under 0.1 eV) mostly due to experimental imprecision with the best fit value that is negative, which is more than 30 billion times smaller than the upper limit of active neutrino masses that are ruled out by W and Z boson decays. In five years of continued data gathering, the direct absolute neutrino mass threshold experimentally should be as low as 0.35 eV if neutrinos are indeed less massive than that as cosmology and neutrino oscillation data suggest (incidentally, the same experiments measuring absolute neutrino mass directly are also used as warm dark matter direct detection experiments but have found nothing so far on that front).

But, Standard Model particles fully account for all such decays to a precision that can rule out the existence of any particles of 45 GeV or less than interact via the weak force with the strength of the other massive fundamental particles in the Standard Model (i.e. all fundamental fermions other than the top quark). So, this provides an independent basis to rule out low mass dark matter particles that interact via the weak force that are not millicharged dark matter, and are also not dark matter that doesn't interact via the weak force at all.

Higgs Boson Decay Constraints

Similarly, if there were a fundamental particle that is not part of the Standard Model with a mass of between 45 GeV and 62.5 GeV that derived its mass through the Higgs mechanism, this particle, rather than the bottom quark, would be the dominant means by which the Higgs boson decays and couldn't be missed at the LHC so far. Indeed, this would be true of any fundamental particle that derived its mass from the Higgs mechanism with a mass from 4.3 GeV (just above the bottom quark mass) to 62.5 GeV (about half the Higgs boson mass). So, observed Higgs boson decays are inconsistent with a dark matter particle that derives its mass from the Higgs mechanism for a large swath of the cold dark matter mass range. So, if there is a dark matter particle with a mass in this mass range, it would instead have to acquire its rest mass via some other mechanism.

Taken together, the W boson, Z boson and Higgs boson constraints combined are among the strongest constraints on the properties of dark matter particles with masses of less than about 8 GeV.

Note On Inconsistent Use Of The Term "Cold Dark Matter"

Note also that there is a terminology disconnect. People who talk about potential dark matter particle candidates distinguish between cold dark matter, warm dark matter and hot dark matter. But, the "cold dark matter" in the lambdaCDM "standard model of cosmology" has a definition loose enough to encompass both warm dark matter and cold dark matter, so long as the dark matter particles don't interact very much at all with either other dark matter particles, or with ordinary matter like nucleons.

No Dark Matter Particle Theory Works In All Circumstances, And There Are Other Alternatives, Although None Of Them Work In All Circumstances Either.

Also, to be clear, there are several ways to explain dark matter phenomena: dark matter particles alone, dark matter particles that have fifth force type interactions either with each other or ordinary matter or both, modifications of gravity alone, or a combination of one or more of the previous possibilities.

As this brief summary suggests, the parameter space available in which dark matter particles alone can provide an explanation is narrow and is on the verge of being over constrained, if it isn't already. If so, it is entirely possible that dark matter particles are not the explanation for dark matter phenomena, in general, or are only part of the explanation. Instead, we also need a new force or a modification of gravity, or both.

This is unfortunate, because while lambdaCDM does a good job of explaining cosmology scale phenomena with a small number of parameters and unambitious assumptions, it can't easily be extrapolated to galaxy cluster and galaxy scales because at those scales plain vanilla cold dark matter doesn't fit the data very well.

In fact, there are no widely supported theories in existence with either a dark matter particle component, or a modified gravity component, that adequately explain the dark matter phenomena data at all scales and in all circumstances.

Steppe Ancestry Reached Switzerland Before Germany; Implications For Etruscan Origins

Bell Beaker blogger reports on a paper about a cemetery in Switzerland with remains from 3300 BCE. Early conference presentations about the site suggest that later publications will show that steppe ancestry in what is now Switzerland ca. 3300 BCE, which is before it appeared in what is now Germany, apparently as part of the Corded Ware culture's early expansion. This is one of the cultures that was most definitively Indo-European linguistically.


A map showing the extent of Etruria and the Etruscan civilization. The map includes the 12 cities of the Etruscan League and notable cities founded by the Etruscans via Wikipedia at the Etruscan origins link below.


Notably, this pre-dates the arrival of the linguistically non-Indo-European Etruscans in Tuscany, Italy, most likely from an immediately prior point of departure in Switzerland, by about two thousand years. What does this imply about Etruscan origins?

Did the Corded Ware people and autochthonous pre-Etruscans who arrived there with the first farmers of Europe (admixed with local hunter-gatherers) co-habit the Swiss plateau with the Corded Ware people for about two thousand years?

The low frequency of the appropriate subtypes of Y-DNA R1a, and the high frequency of the appropriate subtypes of Y-DNA R1b, in modern populations in the region, according to a 2018 paper, as well as largely local mtDNA in ancient Etruscan DNA suggests that while they may have steppe ancestry, it was probably male dominated and closer to Bell Beaker than Corded Ware in origins, and it suggests that there was not much Corded Ware-Etruscan admixture.

Or, were the pre-Etruscans instead, as some ancient historians have suggested, relatively recent emigrants from Southern France to Switzerland who, in turn, continued their exile to a new homeland on the Italian Peninsula? (Or if not there, perhaps from Central Europe?).

Or, is the hypothesis that the Etruscans reached Italy from an immediately prior point of departure in Switzerland simply wrong, as other hypotheses of Etruscan origins dating back to ancient times suggest? Other ancient DNA evidence seems to support the Swiss route hypothesis.


Modern populations color coded by genetic similarity to Etruscan ancient DNA from a 2013 ancient Etruscan mtDNA article. Small Fst values indicate a closer ancestral genetic relationship.

More details information about the ancient DNA results in a published paper could help clarify the issue.

Saturday, September 21, 2019

The Little Known Reincat


No deep message this time.

The Ethical Obligations Of Scientists


Yes, it is funny. But, should scientists spend more time thinking about whether they should, instead of merely whether they can? This certainly isn't part of the culture we instill as we train scientists.

The quote is from Jurassic Park (1993), which is closer to the realm of the possible than you might think.

Friday, September 20, 2019

xkcd: Types of Approximation

Truth!


Mouse over text:

"It's not my fault I haven't had a chance to measure the curvature of this particular universe."

From here.

I am two posts behind on the 3% humor quota, so I'm keeping my eyes open.

How Did The Species Homo Sapiens Emerge In Africa?

A new paper basically looks at the late Middle Paleolithic era hominid remains (basically the pre-Out of Africa era that we associate with Neanderthals in Europe, 350,000 to 130,000 years ago) and tries to use clever statistical tools using the dates, times and physical dimensions of those remains to imagine what kind of admixtures could have produced the earliest anatomically modern human from them and which of those possibilities are most probable. 

The discussion section contains some thoughtful interpretation of the results, but one that is not easily summarized. Click on the link and read the whole thing.

The graph below (weakly) illustrates two of their proposals (my eyes aren't good enough to distinguish between the black one and the gray one) and does provides a nice illustration of the degree to which both modern humans and archaic hominins exhibit physical differences both within categories and from each other. 

Notably, most modern human populations are outside the range of variation probably present in the earliest Homo Sapiens.

The three dimensions illustrated (PC1, PC2 and PC3) describe 84.6% of the morphological differences among the samples. 




Projection of phylogenetic hypotheses 1 (black) and 2 (grey) into the morphospace. The associated shape deformations are displayed next to each PC. Each node represents estimated ancestors’ shapes along with 95% confidence envelopes. Both trees are similar on PC1 and 2, while PC3 highlights differences between both hypotheses within the modern human clade. Modern human populations as follow: 1 to 9 Sub-Saharan Africa; 10–11 Oceania, 12 North Africa, 13–14 Europe, 15 South Asia, 16 to 20 East Asia, 21 North America

This graph is at the heart of their analysis. The term vLCA refers to the "virtual Last Common Ancestors (vLCAs) to all modern humans" inferred from the data.



Morphospaces of the bgPCAs for analyses C (a) and D (b). The ellipses represent the 90% confidence interval for the estimated distribution of the specimens of each population. The vLCAs are closer in shape to the early H. sapiens, as well as the African LMP specimens Flosibad, KNM-ES 11693 and Omo II, while Irhoud 1 is more similar to Neandertals. Modern human populations as follow: 1 to 9 Sub-Saharan Africa; 10–11 Oceania, 12 North Africa, 13–14 Europe, 15 South Asia, 16 to 20 East Asia, 21 North America

The abstract and citation to the paper are as follows: 
The origin of Homo sapiens remains a matter of debate. The extent and geographic patterning of morphological diversity among Late Middle Pleistocene (LMP) African hominins is largely unknown, thus precluding the definition of boundaries of variability in early H. sapiens and the interpretation of individual fossils. Here we use a phylogenetic modelling method to predict possible morphologies of a last common ancestor of all modern humans, which we compare to LMP African fossils (KNM-ES 11693, Florisbad, Irhoud 1, Omo II, and LH18). Our results support a complex process for the evolution of H. sapiens, with the recognition of different, geographically localised, populations and lineages in Africa – not all of which contributed to our species’ origin. Based on the available fossils, H. sapiens appears to have originated from the coalescence of South and, possibly, East-African source populations, while North-African fossils may represent a population which introgressed into Neandertals during the LMP.
Aurélien Mounier & Marta Mirazón Lahr, "Deciphering African late middle Pleistocene hominin diversity and the origin of our species" 10 Nature Communications Article number: 3406 (September 10, 2019) (open access).

The hominin remains considered in the analysis are as follows:
In Northern Africa, the site of Jebel Irhoud has yielded multiple fossils since the 1960s, including a complete skull (Irhoud 1), originally dated to 130–190 ka. Recent excavations at the site have yielded additional fossils (in particular a partial upper face, Irhoud 10, and a mandible, Irhoud 11), and a new date estimate of 315 ka. 
Well-preserved LMP hominins are more numerous in Eastern Africa. The Singa calvarium from Sudan is dated to 133 ka. In Ethiopia, the Omo Kibish specimens, Omo I and Omo II, are dated to 200 ka, and the three specimens from Herto, which include a complete adult cranium (BOU-VP16/1) and a juvenile calvarium (BOU-VP16/5), with an estimated date of 160 ka. In Kenya, the Guomde calvarium (KNM-ER 3884), which lacks most of the facial and frontal bones, has been dated to 270–300 ka with ɤ-ray spectrometry, while an age of 200–300 ka has been suggested for the nearly complete Eliye Springs skull (KNM-ES 11693) on the basis of its morphology. 
Further South, a 200–300 ka cranium (LH18) was discovered in the Ngaloba Beds at Laetoli (Tanzania), and in South Africa, the site of Florisbad yielded a partially preserved cranium dated to 259 ka. Lastly, the recently discovered remains of H. naledi, dated to 236–335 ka, add major complexity to the LMP hominin record of southern Africa.
It bears noting also that one of the main reasons that Central and West Africa are not within the realm of possible places of origins for modern humans considered in this study is that we have no late Middle Paleolithic hominin remains from those places. But, this is something that could be due simply to poor conditions for preserving bones in these tropical environments and a lack of resources devoted to hunting for those remains. The absence of evidence is not necessarily evidence of absence, and genetic evidence points to the existence of archaic hominins in Central Africa and West Africa into the Upper Paleolithic era until the Holocene era (i.e. about 50,000 to 10,000 years ago).

Thursday, September 19, 2019

1700 Posts

This is post number 1700 at this blog. And, while the pace of posts has slide a bit, it is still a blog that is alive and well.

Measurements Of Two Neutrino Oscillation Parameters Improved

A paper combining two sets of neutrino oscillation data from different, but similar, experiments, improves the precision with which two of the six observable neutrino oscillation parameters is improved by more than 30%. The paper conveniently states all of its important conclusions in a single paragraph which I have cut and pasted below:


PDG reports a value for sin^2(theta13) of 0.0218 ± 0.0007 which can be converted exactly to a theta13 value of 8.49º compared to a value from this report which is a theta13 value of 8.68º.

The delta squared ee mass is not exactly comparable to any of the quantities reported in PDG either. Numerically, the result is similar to the one for the delta squared 32 mass which is 0.002444 ± 0.000034 eV^2 (the square root of which is 49 meV). It is possible to do a conversion  to 
Δm using the values of sin and Δm. The conversion from delta squared ee to delta squared mm is to subtract approximately 0.00051 from the delta squared ee measurement. So this work's combined RENO and Daya Bay result is equivalent to 0.002540 (to the same number of significant digits). This is higher than, but consistent at one sigma with, the PDG value.
 It is