Dietary, Cultural, and Pathogens-Related Selective Pressures Shaped Differential Adaptive Evolution among Native Mexican Populations

Abstract

Native American genetic ancestry has been remarkably implicated with increased risk of diverse health issues in several Mexican populations, especially in relation to the dramatic changes in environmental, dietary, and cultural settings they have recently undergone. In particular, the effects of these ecological transitions and Westernization of lifestyles have been investigated so far predominantly on Mestizo individuals. Nevertheless, indigenous groups, rather than admixed Mexicans, have plausibly retained the highest proportions of genetic components shaped by natural selection in response to the ancient milieu experienced by Mexican ancestors during their pre-Columbian evolutionary history. These formerly adaptive variants have the potential to represent the genetic determinants of some biological traits that are peculiar to Mexican people, as well as a reservoir of loci with possible biomedical relevance. To test such a hypothesis, we used genome-wide genotype data to infer the unique adaptive evolution of Native Mexican groups selected as reasonable descendants of the main pre-Columbian Mexican civilizations. A combination of haplotype-based and gene-network analyses enabled us to detect genomic signatures ascribable to polygenic adaptive traits plausibly evolved by the main genetic clusters of Mexican indigenous populations to cope with local environmental and/or cultural conditions. Some of these adaptations were found to play a role in modulating the susceptibility/resistance of these groups to certain pathological conditions, thus providing new evidence that diverse selective pressures have contributed to shape the current biological and disease-risk patterns of present-day Native and Mestizo Mexican populations.

Hunter-gatherer admixture facilitated natural selection in Neolithic European farmers

“…MUC19 also plays a role in immunity, and was found to be under selection in Central Mexican indigenious populations 30 . OPRM1 is documented to contribute towards skin pigmentation in Native American and East Asian populations 31,32 , while a HRNR haplotype linked to atopic dermatitis may have seen a selective sweep in East Asia alone 33 ROR1 is adjacent to PGM1 which may have undergone selection in Mexican populations 34 . Similarly, the LAD analysis finds some genes with previous reports of selection; HECW2 has been identified to be under selection in Khomani San 35 , a southern African group with recent hunter-gatherer lifestyle, while PKP2 was similarly seen to be under selection in the Yoruba in west Africa in the same study.…”

Indigenous people from Amazon show genetic signatures of pathogen-driven selection

“…Furthermore, selection did not necessarily occur in the postcontact period; if it did occur, it may not have been strong or widely distributed enough to be detected in admixture mapping analyses. In Southern Mexican populations, several putative genes related to immune and inflammatory responses were identified under natural selection, including PPP3CA ( 53 ). The forests in this region are abundant with parasites such as T. cruzi and Leishmania mexicana , which are endemic.…”

Differential distribution of gene polymorphisms associated with hypercholesterolemia, hypertriglyceridemia, and hypoalphalipoproteinemia among Native American and Mestizo Mexicans

“…The implications of these findings require addressing the role of the interrelationship between diet-related adaptive alleles and the current diet of the population. In this sense, NA groups have followed a frugal lifestyle for millennia in which lipid-related alleles may have been positively selected to cope with the Paleolithic and Neolithic Mesoamerican environments[ 39 ]. Their traditional diets mainly contained low amounts of saturated fats and were high in mono- and polyunsaturated vegetal fats and high complex carbohydrates which are protective against lipid-related chronic diseases despite the host’s “risk alleles”[ 40 , 41 ].…”