Wednesday, March 6, 2024

Dark Matter Is Not Made Up Of Primordial Black Holes

We find that compact objects in the mass range from 1.8×10^−4M⊙ to 6.3M⊙ cannot compose more than 1% of dark matter, and compact objects in the mass range from 1.3×10^−5M⊙ to 860M⊙ cannot make up more than 10% of dark matter. This conclusively rules out primordial black hole mergers as a dominant source of gravitational waves.
From: https://arxiv.org/abs/2403.02386 Confirmed from the same data at https://arxiv.org/abs/2403.02398

Wednesday, February 21, 2024

The Population Genetics Of India

A new preprint has no really shocking results, but provides many refinements to our previous understanding of historical genetics in India. Credit where credit is due for acknowledging the existing of early waves of modern humans in India even though they haven't left much of a genetic trace in modern populations. It also seems that there was secondary Neanderthal admixture in South Asia in addition to the admixture that took place in the Middle East.
India has been underrepresented in whole genome sequencing studies. We generated 2,762 high coverage genomes from India––including individuals from most geographic regions, speakers of all major languages, and tribal and caste groups––providing a comprehensive survey of genetic variation in India. With these data, we reconstruct the evolutionary history of India through space and time at fine scales. 
We show that most Indians derive ancestry from three ancestral groups related to ancient Iranian farmers, Eurasian Steppe pastoralists and South Asian hunter-gatherers. 
We uncover a common source of Iranian-related ancestry from early Neolithic cultures of Central Asia into the ancestors of Ancestral South Indians (ASI), Ancestral North Indians (ANI), Austro-asiatic-related and East Asian-related groups in India. 
Following these admixtures, India experienced a major demographic shift towards endogamy, resulting in extensive homozygosity and identity-by-descent sharing among individuals. 
At deep time scales, Indians derive around 1-2% of their ancestry from gene flow from archaic hominins, Neanderthals and Denisovans. By assembling the surviving fragments of archaic ancestry in modern Indians, we recover ∼1.5 Gb (or 50%) of the introgressing Neanderthal and ∼0.6 Gb (or 20%) of the introgressing Denisovan genomes, more than any other previous archaic ancestry study. Moreover, Indians have the largest variation in Neanderthal ancestry, as well as the highest amount of population-specific Neanderthal segments among worldwide groups. 
Finally, we demonstrate that most of the genetic variation in Indians stems from a single major migration out of Africa that occurred around 50,000 years ago, with minimal contribution from earlier migration waves
Together, these analyses provide a detailed view of the population history of India and underscore the value of expanding genomic surveys to diverse groups outside Europe.
Elise Kerdoncuff, et al., "50,000 years of Evolutionary History of India: Insights from ∼2,700 Whole Genome Sequences"  (February 17, 2024). https://www.biorxiv.org/content/10.1101/2024.02.15.580575v1

Aztec Human Sacrifice

"For the re-consecration of the Great Pyramid of Tenochtitlan in 1487, the Aztecs reported that they killed about 80,400 prisoners over the course of four days. According to Ross Hassig, author of Aztec Warfare, "between 10,000 and 80,400 persons" were sacrificed in the ceremony."
From Wikipedia.

Recall that this city had a population of 200,000 non-prisoner residents, which while huge for the time, is only about three times greater than the number of people sacrificed.