Evidence grows that peopling of the Americas began more than 20,000 years ago

Anthropic cut marks in extinct megafauna bones from the Pampean region (Argentina) at the last glacial maximum

The initial peopling of South America is a topic of intense archaeological debate. Among the most contentious issues remain the nature of the human-megafauna interaction and the possible role of humans, along with climatic change, in the extinction of several megamammal genera at the end of the Pleistocene. In this study, we present the analysis of fossil remains with cutmarks belonging to a specimen of Neosclerocalyptus (Xenarthra, Glyptodontidae), found on the banks of the Reconquista River, northeast of the Pampean region (Argentina), whose AMS 14C dating corresponds to the Last Glacial Maximum (21,090-20,811 cal YBP). Paleoenvironmental reconstructions, stratigraphic descriptions, absolute chronological dating of bone materials, and deposits suggest a relatively rapid burial event of the bone assemblage in a semi-dry climate during a wet season. Quantitative and qualitative analyses of the cut marks, reconstruction of butchering sequences, and assessments of the possible agents involved in the observed bone surface modifications indicate anthropic activities. Our results provide new elements for discussing the earliest peopling of southern South America and specifically for the interaction between humans and local megafauna in the Pampean region during the Last Glacial Maximum.

The Aldehyde Dehydrogenase ALDH2*2 Allele, Associated with Alcohol Drinking Behavior, Dates Back to Prehistoric Times

Human alcohol-consumption behavior is partly genetically encoded. The alcohol consumption of 987 residents in Keelung, Taiwan, was evaluated by using the Alcohol Use Disorder Identification Test (AUDIT). We assessed ~750,000 genomic variants of 71 residents who drank hazardously (AUDIT score ≥ 8) and 126 residents who did not drink in their daily lives (AUDIT score = 0), using high-density single nucleotide polymorphism (SNP) arrays. The rs671 G > A manifests the highest significance of the association with drinking behavior (Fisher’s exact P = 8.75 × 10⁻⁹). It is a pleiotropic, non-synonymous variant in the aldehyde dehydrogenase 2 (ALDH2) gene. The minor allele “A”, commonly known as ALDH2*2, is associated with non-drinkers. Intriguingly, identity-by-descent haplotypes encompassing genomic regions with a median length of 1.6 (0.6–2.0) million nucleotide bases were found in all study participants with either heterozygous or homozygous ALDH2*2 (n = 81 and 13, respectively). We also analyzed a public-domain dataset with genome-wide genotypes of 2000 participants in Guangzhou, a coastal city in Southern China. Among them, 175 participants have homozygous ALDH2*2 genotype, and again, long ALDH2*2-carrying haplotypes were found in all 175 participants without exceptions. The median length of the ALDH2*2-carrying haplotype is 1.7 (0.5–2.8) million nucleotide bases. The haplotype lengths in the Keelung and Guangzhou cohorts combined indicate that the origin of the ALDH2*2 allele dates back to 7935 (7014–9381) years ago. In conclusion, the rs671 G > A is the leading genomic variant associated with the long-term drinking behavior among residents of Keelung, Taiwan. The ALDH2*2 allele has been in Asian populations since prehistoric times.

Human molecular evolutionary rate, time dependency and transient polymorphism effects viewed through ancient and modern mitochondrial DNA genomes

Human evolutionary genetics gives a chronological framework to interpret the human history. It is based on the molecular clock hypothesis that suppose a straightforward relationship between the mutation rate and the substitution rate with independence of other factors as demography dynamics. Analyzing ancient and modern human complete mitochondrial genomes we show here that, along the time, the substitution rate can be significantly slower or faster than the average germline mutation rate confirming a time dependence effect mainly attributable to changes in the effective population size of the human populations, with an exponential growth in recent times. We also detect that transient polymorphisms play a slowdown role in the evolutionary rate deduced from haplogroup intraspecific trees. Finally, we propose the use of the most divergent lineages within haplogroups as a practical approach to correct these molecular clock mismatches.