Understanding the Adaptive Evolutionary Histories of South American Ancient and Present-Day Populations via Genomics.

John Lindo,Michael Degiorgio

doi:10.3390/genes12030360

Abstract

The South American continent is remarkably diverse in its ecological zones, spanning the Amazon rainforest, the high-altitude Andes, and Tierra del Fuego. Yet the original human populations of the continent successfully inhabited all these zones, well before the buffering effects of modern technology. Therefore, it is likely that the various cultures were successful, in part, due to positive natural selection that allowed them to successfully establish populations for thousands of years. Detecting positive selection in these populations is still in its infancy, as the ongoing effects of European contact have decimated many of these populations and introduced gene flow from outside of the continent. In this review, we explore hypotheses of possible human biological adaptation, methods to identify positive selection, the utilization of ancient DNA, and the integration of modern genomes through the identification of genomic tracts that reflect the ancestry of the first populations of the Americas.

Highlights

When the first people arrived in South America, many thousands of years ago, they encountered a wide range of environments that greatly differed from their migratory point of origin: Beringia
Speaking, positive selection signals may be dampened in Andean highland populations due to population collapses that occurred after European contact in the region, which may have been as high as 80% according to historical estimates [13]
Was the ancient population collapse in this region found to be less severe compared to other parts of South America, but the population shows patterns consistent with positive selection on variants that may be involved in the immune response to smallpox [7]

Summary

Introduction

When the first people arrived in South America, many thousands of years ago, they encountered a wide range of environments that greatly differed from their migratory point of origin: Beringia. Ancient genomics has the power and potential to refine our understanding of how the first settlers successfully established populations via adaptive evolutionary events This power can be utilized to discover ancient pathogens, which are strong motivators for natural selection, and may have prompted local biological adaptation. Contrary to notions of pristine environments before the arrival of Europeans, the early populations likely dealt with pathogens that may have prevented initial settlement success without adaptation. This scenario is likely in regions where disease vectors are present, such as mosquitos, or in tropical regions where the risk of parasitic infection is high. We will discuss more recent adaptation in living populations that may have been the result of admixture with migrant populations after European contact

High-Altitude Adaptation

Ultraviolet Radiation

Adaptive and Plastic Responses to Culture

Ancient Pathogens and European-Borne Disease

Methods for Detecting Positive Selection

Conclusions