Arecent paper published in Science (Elena S. Gusareva et al., From North Asia to South America: Tracing the longest human migration through genomic sequencing. Science388,eadk5081(2025).DOI:10.1126/science.adk5081), looks into the peopling of America, and mentions that "Over the past 10,000 years, all four Native South American lineages have experienced population declines ranging from 38 to 80%." However, it does not consider the impact of population decline on genetic diversity. Just imagine the lost variants when such a bottleneck takes place (most of the people died in the aftermath of the European discovery and conquest of the New World).
The authors state that: (my comments in bold face)
"We were not able to identify a specific Siberian group as the direct ancestors of Native Americans owing to deep divergence and limited genetic continuity. [we'd expect this since 25ky have gone by since both groups split] However, west Beringian populations remain closely related to Native Americans. Koryaks and Inuit show 5 and 28% Native American ancestry, respectively, owing to gene flow between 700 and 5100 ya." [Inuit are late arrivals so they don't count when we talk about the early peopling of America]
The paper then uses the high ratios of runs of homozygosity (ROHs) among Amerindians to suggest that they are due to interbreeding and bottlenecks in the population (which is reasonable). However we should also consider the fact that 80 to 90% of American natives were wiped out by the diseases brought to America by the European voyages of conquest and discovery. Those that survived, did so because they had a selective advantage against these diseases, and Selection plays an important role in the formation of ROHs: they might be favored by natural selection, and this would lead to a higher frequency of ROHs in the population.
The same argument can be made for the lower diversity of human leukocyte antigen (HLA) genes among Amerindians. Natural selection promotes a higher variety to fend off disease. But with a massive death toll like the one triggered by the European Conquest of 1492 HLA variants that had been effective until that date, became extinct, and the few lineages survived were then selected for as they protected againsts the new Eurasian-African pathogens brought to America by the conquerors. Furthermore, Europeans admixed with the survivors, as did the African slaves brought to America. This adds even more complexity to the matter.
For an insight into the great dying caused by the conquest, see this article: The immunogenetic impact of European colonization in the Americas (Collen Evelyn Jane, Johar Angad Singh, Teixeira João C., and Llamas Bastien. Frontiers in Genetics Vol 13-2022 doi=10.3389/fgene.2022.918227): "Ancestry-specific identity-by-descent methods predicted that the ancestors of present-day Puerto Ricans underwent a reduction in effective population size to less than 100 individuals at the time of European arrival. Large-scale population (and therefore diversity) declines were also inferred in other regions among the Southern Chilean Huilliche–Pehuenche (an estimated decline of 96%), the Mexican Mixe (94%), and the Tsimshian (57%) around the same time."
Those who died took their HLAs with them, the survival of the fittest wiped out ancient lineages that had coped with New World pathogens for +30,000 years.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2025 by Austin Whittall ©
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