DES Reduces S8 Tension

One of the persistent tensions in cosmology measurements, that has attracted less attention from the general public than the Hubble tension, is the value of a parameter called S8 (which measures "clustering amplitude" at a cosmological level) estimated from the cosmic background radiation measurements and the measurement from other means. New data from the Dark Energy Survey (DES) weakens that tension.

Cosmology from weak gravitational lensing has been limited by astrophysical uncertainties in baryonic feedback and intrinsic alignments. 

By calibrating these effects using external data, we recover non-linear information, achieving a 2% constraint on the clustering amplitude, S8, resulting in a factor of two improvement on the ΛCDM constraints relative to the fiducial Dark Energy Survey Year 3 model. The posterior, S8 = 0.832+0.013−0.017, shifts by 1.5σ to higher values, in closer agreement with the cosmic microwave background result for the standard six-parameter ΛCDM cosmology. 

Our approach uses a star-forming 'blue' galaxy sample with intrinsic alignment model parameters calibrated by direct spectroscopic measurements, together with a baryonic feedback model informed by observations of X-ray gas fractions and kinematic Sunyaev-Zel'dovich effect profiles that span a wide range in halo mass and redshift. Our results provide a blueprint for next-generation surveys: leveraging galaxy properties to control intrinsic alignments and external gas probes to calibrate feedback, unlocking a substantial improvement in the precision of weak lensing surveys.

Leah Bigwood, et al., "Confronting cosmic shear astrophysical uncertainties: DES Year 3 revisited" arXiv:2512.04209 (December 3, 2025).

New astronomy observations also strongly constrains multi-field cosmological inflation models. And, another study combining data from multiple collaborations, strongly disfavors cosmological "inflation models preferred by Planck alone, such as Higgs, Starobinsky, and exponential α-attractors, in favor of other models, such as polynomial α-attractors," based upon its new measurements of cosmological parameter n(s) (the primordial power spectrum).

Finally, there were several new preprints today exploring the WIMP dark matter hypothesis, which is irritating because the WIMP dark matter hypothesis has been almost completely ruled out by a variety of independent means.

Volcano Driven Famine Brought Black Plague Bearing Fleas In Grain Shipments To Europe In 1347

Volcanic eruptions in 1345 CE, lead to crop failures from 1345 to 1347 in the Mediterranean. This led Italians to import grain from Mongols near the sea of Azov region (currently between Ukraine and Russia) in 1347, where a black plague infestation was already present, spreading the plague to Europe. The black plague then ran rampant across Europe from 1347 to 1353 killing an immense share of the population of Europe (up to 60% of some towns and villages). 

Several years of famine also probably weakened the immune systems of most Europeans, impairing their ability to fight to black plague bacteria and making its lethality rate greater.

This black plague pandemic actually started in "the arid foothills of the Tien Shan mountains west of Lake Issyk-Kul in modern-day Kyrgyzstan" in 1338, but it took nine more years for it to reach Europe. While the volcano induced famines in Europe sped its spread, arguably its eventual arrival in Europe, sooner or later, was almost inevitable.

Human history is pockmarked with periods of death and destruction on unimaginable scales. Of these calamitous epochs, one stands out: The Black Death. The mid 14th century scourge killed tens of millions of people in Europe, Asia, and Africa and changed the course of history—marking the tail end of the Middle Ages and ushering in the cultural reawakening of the Renaissance by disrupting society, the feudal system, and economies across the continent. 

Researchers have long known the Black Death’s central villain: the bacterium Yersinia pestis, which caused the bubonic plague that swept through towns and villages with a mortality rate of up to 60 percent. Experts also know this microbial agent was spread by fleas, borne on the backs of rodent pests and maybe domestic animals, and passed between humans through the air and bodily fluids. But historians have had a tougher time recreating the sequence of events that initially started the devastating pandemic. 

Now, a pair of scientists have found new clues hidden in tree rings. By looking at these rings in the Spanish Pyrenees—as well as details in historical accounts of the time—they suggest that heightened volcanic activity sometime around 1345 may have sparked a famine, kicking off the sequence of events that eventually led to the Black Death raging through Eurasia from 1347 and 1353. They published their findings today in Communications Earth & Environment. . . . 

Here is the model Bauch and his colleague Ulf Büntgen, a dendrochronologist at Cambridge University, propose. As yet unknown volcanic eruptions ejected huge amounts of ash and gases into the atmosphere around 1345, causing drops in annual temperatures that persisted for several years. The cross sections from living and relic trees that the researchers studied had “blue rings,” denoting abnormally cold and wet summer growth seasons, in 1345, 1346, and 1347. Additional accounts from the time considered by Bauch and Büntgen tell of abnormal cloudiness and dark lunar eclipses, further hints of volcanic activity. This sustained cooling could have caused widespread crop failure across the Mediterranean. 

The resulting food shortages drove merchants in the maritime republics of Venice, Genoa, and Pisa to increase imports of grain from the Mongols living around the sea of Azov in 1347. Along with shipments of grain coursing across established trade routes came plague-infested fleas. Once Y. pestis and the fleas that carried it landed in Europe, the pathogen jumped to rats, mice, and perhaps domesticated animals. Eventually the disease hopped to humans, and people began transmitting it in densely packed population centers. The rest is a dark part of history. 

“For more than a century, these powerful Italian city states had established long-distance trade routes across the Mediterranean and the Black Sea, allowing them to activate a highly efficient system to prevent starvation,” said Bauch. “But ultimately, these would inadvertently lead to a far bigger catastrophe.” 

From a Facebook post by Nautilus Magazine. 

The introduction to the published paper states:

Recent advances in paleogenetic research now demonstrate that the Black Death was caused by the bacterium Yersinia pestis, which is likely to persist in different forms in natural reservoirs, including wildlife rodent populations. Investigations of great gerbil (Rhombomys opimus) populations in Kazakhstan, for instance, have outlined how the bacterium can be transmitted from one mammalian host to another by hematophagous insect vectors, such as fleas. The zoonotic disease, however, only occasionally spills over to domestic mammals and humans, and so far three pandemics have been documented: The Justinianic plague from circa 541 to the second half of the 8th century CE; the second pandemic starting around 1338 CE in central Asia and later outbreaks in the Mediterranean region and Europe until the early 19th century CE; and the third plague pandemic that had its origin in the 1770s in China and is arguably still prevalent in endemic rodent populations in different parts of the world.

A combination of archaeological, historical and ancient genomic data proposes that the causal agent of the second plague pandemic most likely originated from the arid foothills of the Tien Shan mountains west of Lake Issyk-Kul in modern-day Kyrgyzstan. A genetically distinct strain of the bacterium was then transmitted along ancient trade routes and entered Europe via the northern Black Sea region in the early 1340s. While changes in long-distance maritime grain trade have been introduced as a possible explanation for the import of plague-infected fleas to Venice and other Mediterranean harbour towns in 1347 CE, this chain of arguments excludes alternative transmission pathways, such as human-to-human infection or the transport of rodents and goods. Intriguingly, the role climatic changes and associated environmental factors may have played in the onset and establishment of the Black Death remains controversial amongst scholars from the natural and social sciences and the humanities.

Despite an ever-growing understanding of the evolution, origin and transmission of Yersinia pestis during the second plague pandemic, it is still unclear if the bacterium was frequently re-introduced into Europe or if natural reservoirs of the bacterium ever existed there. Recent insights into plague ecology include aspects of prolonged flea survival without human and/or rodent hosts but feeding opportunities on grain dust during long-term food shipments. Empirical evidence from around 1900 CE may therefore be considered as a possible explanation of how Yersinia pestis could have arrived in medieval Italy. While there is so far no convincing argument to pre-date the beginning of the second plague pandemic into the 13th century CE, changes in socio-economic structures, political institutions and trade networks since the second half of the 13th century possibly impacted the course of the second plague pandemic.

Here, we show that interdisciplinary investigations into the entanglements between weather, climate, ecology and society well before the Black Death are essential to understand the exceptional level of spread and virulence that made the first wave of the second plague pandemic so deadly. Based on annually resolved and absolutely dated reconstructions of volcanically forced cooling, transregional famine, and changes in long-distance maritime grain trade from 1345–1347 CE, we argue that the onset of the Black Death most likely resulted from a complex interplay of natural and societal factors and processes. Although this unique spatiotemporal coincidence of many influences seems rare, our findings emphasise the increased likelihood of zoonotic infectious diseases to suddenly emerge and rapidly translate into pandemics in both, a globalised and warmer world with COVID-19 just being the latest warning sign.

A Quick Recap Regarding The Indo-European Languages

 

This post is pretty much entirely old news that I've blogged about previously. But every once and a while it is worth recapping the basics for folks who are new to the discussion (and quite frankly, I just haven't had the time lately to post in more depth about more up to date developments in this field).

The Indo-European Languages

More than 40% of humans alive today speak an Indo-European language as their mother tongue, some 3.4 billion people (and well north of 50% if you count second-language learners). The top ten are:

Spanish ~484 million

English ~390 million

Hindi ~345 million

Portuguese ~250 million

Bengali ~242 million

Russian ~145 million

Punjabi ~120 million

Marathi ~83 million

Urdu ~78 million

German ~76 million

Via Razib Khan

It is also worth noting that the 'Indo" part of "Indo-European", basically, languages derived from Sanskrit (formally known as the Indo-Aryan language family) as it existed ca. 1500 BCE, is a huge part of the total with about 868 million speakers (about 39% of the top ten) among the top ten Indo-European languages, compared to about 1365 million for European languages (including native speakers of versions of those languages spoken mostly in their New World colonies in North America and South America, and in Australia and New Zealand) among the top ten Indo-European languages. There are more Sanskrit derived language speakers in the top ten than there are Latin derived (Romance) language speakers in the top ten.

Where Did The Indo-European Languages Come From?

All Indo-European languages are derived from the Proto-Indo-European language spoken by about 10,000-20,000 people in what is now Ukraine, probably making up several tribes of people with a mixed herder-farmer form of subsistence, around 3000 BCE. 

Speculatively, Proto-Indo-European may have arisen from a fusion of the language of an early herder community in the region and an early farmer community in the reegion.

The Indo-European language expansion had a large demic component (i.e. it involved Indo-Europeans people replacing or demographically swamping existing populations), although the extent that this happened varied considerably, from about 90% replacement in the British Isles ca. 2500-2400 BCE, to less than 15% in parts of Southern India (where Indo-European languages are currently not widely spoken in daily life as a first language). 

Indo-European Languages In South Asia

In India, the Indo-European demic component in places where Dravidian languages are now the predominant native language, is probably the product of a first wave of Indo-European conquest that covered almost all of the Indian subcontinent and led to the extinction of most of the then existing Dravidian language. This conquest was then followed by a Dravidian reconquest of most of the formerly Dravidian linguistic territory by speakers of a sole surviving Dravidian language in a small area that managed to escape language shift at the hands of the Indo-Aryan conquerors. The reconquest kept the invader's proto-Hindu religion (maintained to this day by members of a broad Brahmin caste called a "varna" in South India, who have significant ancestry from those invaders), however, mostly intact but with regional influences. Subsequent waves of Indo-European people migrated to Northern India after this reconquest, but not to Southern India.

This explains why the last date of mass Indo-European admixture is older in Southern India than in Northern India (which is mostly Indo-European speaking), why the Dravidian language family looks so young despite the fact that the most plausible time for it to emerge is in the South Asian Neolithic Revolution ca. 2500 BCE (not all that different from the Proto-Indo-European language, despite the fact that the Indo-European language family that is far more diverse and has far more time depth), why Indo-European ancestry found across all of India but in varying proportions by location and caste, and why Indo-European language speaking Hindus are much more likely to be vegetarians than Dravidian language speaking Hindus (vegetarianism was one aspect of the invader's religion that didn't survive the Dravidian reconquest).

Their expansion is summarized in  broad brush without some of the finer details in the map above, which is generally accurate but subject to revision as new evidence from archaeology and ancient DNA and historical linguistics refines it. 

Indo-European Anatolian Languages.

Probably the most controversial part of the map pertains to how the Anatolian Indo-European languages (which are now extinct) relate to the other Indo-European languages. 

These languages are greatly diverged from other Indo-European languages (and there is not much Steppe ancestry in ancient DNA from Neolithic and Bronze Age Anatolia), which has led some historical linguists to try to come up with contorted theories to explain what seems like a very old date of divergence of the Anatolian languages from the other Indo-European languages, in the face of genetic evidence, ancient historical records from nearby areas, and archaeology, that don't seem to fit this narrative.

For example, some scholars think that the Indo-European languages originated in Anatolia in the Neolithic era and then had a secondary expansion to almost everywhere else sometime after 3000 BCE. This well-intentioned effort to fit the linguistic distinctiveness of the Anatolian languages to the other evidence is wrong.

In my informed but not credentialed opinion, the Indo-European languages originated on the Steppe, and one wave of Indo-European migrants travelled to Anatolia around 2000 BCE (at a time when Indo-Europeans were rapidly expanding in all directions due to a climate driven collapse of civilizations in Europe and India at the time). The Anatolian languages are more distinct from other Indo-European languages. But this is not because the time depth of their relationship is older. 

Instead, it is because unlike most other places that the Indo-European languages expanded to, the local copper age/early Bronze Age civilization in Anatolia has not collapsed to nearly the same extent, so the Anatolian languages spread more through elite dominance than demically, and the Anatolian languages had a stronger substrate influence from the Hattic language spoken in the region before it was conquered by an Indo-European elite in the centuries following 2000 BCE from a couple of modest Indo-European villages, in a process of conquest that is historically attested that ultimately gave rise to a Hittite empire. Most historically attested Indo-European Anatolian languages are known only after the Hittite language fractured after the Hittite Empire collapsed in the regional phenomena known as Bronze Age collapse, ca. 1200 BCE, in a process similar to the fragmentation of the Romance languages after the fall of the Roman Empire. Only two or three of the Anatolian languages (including Hittite) predate this fragmentation.

The Anatolian languages also seem more distinct because the substrate languages for Indo-European languages in Europe were all part of the same Neolithic Paleo-European language family of the first farmers of Europe (who largely replaced early European hunter-gatherers), derived from their common origins in Western Anatolia (before Anatolia experienced a language shift in the Copper Age or early Bronze Age as invaders from the Caucuses and Western Asian highlands conquered its Neolithic civilization).

Some of what looks like shared Indo-European roots in European Indo-European languages is really the product of a shared Paleo-European linguistic substrate that is absent in the Anatolian languages and Tocharian languages (which are the most diverged from other European language causing some linguists to assume that the greater divergence represented greater time depth of the divergence).

The Tocharian language family

Another, less intense controversy in Indo-European historical linguistics is how the extinct Tocharian language family fits into the overall picture.

The Tocharian languages, attested in written form and spoken historically in the Tarim Basin of Central Asia, is the attested Indo-European language family that is probably most conservative with respect to Proto-Indo-European. This is because it experienced far less contact with other languages and had almost no substrate influence as the Tocharians moved into basically unoccupied territory. In the same way and for the same reasons, Icelandic is the most conservative Germanic language, the Spanish of the American Southwest is the most conservative Spanish dialect, and the Appalachian English dialect is closest in pronunciation to Shakespearian English. 

In my own life, I've personally seen that the Korean language dialect of Korean migrants to the U.S. is more conservative than that of Koreans who stayed in Korea. Languages evolve most slowly at the frontiers if they have limited language contract with other languages (something that obviously isn't true of second generation and later Korean language speakers in the U.S., of course).