What uniparental genetic markers tell us about the prehistoric human colonization of the Americas

From the perspective of uniparental markers, the view of the human prehistoric settlement of America is that it resulted from a single main migration after the Last Glacial Maximum, following a period of prolonged stasis in Beringia. These pioneers rapidly expanded across a continent previously uninhabited by humans, forming isolated population groups that became genetically distinct. Ancient DNA studies and whole genome analyses have confirmed this view, revealing a remarkable complexity in the ancestries of the involved populations. In this work, I have reanalyzed all publicly available mitochondrial DNA and Y-chromosome haplogroups in the American population using simple phylogenetic and phylogeographic methodologies. The results provide a genetic perspective opposed to the currently established model. The arrival of the American settlers occurred more than 30,000 years ago, preceding the LGM. As genomic studies have uncovered, at least two Asian populations contributed to the ancestry of the immigrant population. Low population density and climatic deterioration led to a long period of demographic eclipse, during which small bands of hunter-gatherers made long journeys in search of favorable niches. After the LGM, the climate improved, and demographic expansions occurred in multiple independent centers. The founding and expansion ages of the uniparental haplogroups indicate that these centers were in South America, particularly the Colombian isthmus, the Andean region, the Southern Cone, and the Amazon. Subsequent dispersals occurred in North America, one involving mitochondrial haplogroups A2, C1, and D1, but not B2, and another, of lesser magnitude, represented by the expansion of haplogroups C4c and X2a. This work offers a previously unexplored model for the colonization of the Americas.