The initial peopling of South America is largely unresolved, in part because of the unique distribution of genetic diversity in native South Americans. On average, genetic diversity estimated within Andean populations is higher than that estimated within Amazonian populations. Yet there is less genetic differentiation estimated among Andean populations than estimated among Amazonian populations. One hypothesis is that this pattern is a product of independent migrations of genetically differentiated people into South America. A competing hypothesis is that there was a single migration followed by regional isolation. In this study we address these hypotheses using mtDNA hypervariable region 1 sequences representing 21 South American groups and include new data sets for four native Peruvian communities from Tupe, Yungay, and Puno. An analysis of variance that compared the combined data from western South America to the combined data from eastern South America determined that these two regional data sets are not significantly different. As a result, a migration from a single source population into South America serves as the simplest explanation of the data.
Abstract. Molecular-based characterizations of Andean peoples are traditionally conducted in the service of elucidating continental-level evolutionary processes in South America. Consequently, "western" Andean population genetic variation is often represented in relation to "eastern" variation among Amazon and Orinoco River Basin populations. This west-east contrast in patterns of population genetic variation is typically attributed to large-scale phenomena, such as dual founder colonization events and/or differing long-term microevolutionary histories.However, alternative explanations that consider the nature and causes of population genetic diversity within the Andean region remain underexplored.Here we examine population genetic diversity in the Peruvian Central Andes using mtDNA HVI and Y-chromosome STR data from 17 newly sampled 3 populations combined with published samples. Using this geographically comprehensive data set, we first re-assess the currently accepted pattern of western vs. eastern population genetic structure, which our results ultimately reject: mtDNA population diversities were lower, rather than higher, within Andean versus eastern populations, and only highland Y-chromosomes exhibited significantly higher within-population diversities compared to eastern groups.Multiple populations, including several highland samples, exhibited low genetic diversities for both genetic systems. Second, we explore whether the implementation of Inca state and Spanish colonial policies starting at about A.D. 1400 could have substantially restructured population genetic variation, and consequently constitute a primary explanation for the extant pattern of population diversity in the Peruvian Central Andes. Our results suggest that Peruvian Central Andean population structure cannot be parsimoniously explained as the sole outcome of combined Inca and Spanish policies on the region's population demography: Highland populations differed from coastal and lowland populations in mtDNA genetic structure only; highland groups also show strong evidence of female-biased gene flow and/or effective sizes relative to other Peruvian ecozones. Taken together, these findings indicate that population genetic structure in the Peruvian Central Andes is considerably more complex than previously reported and that characterizations of, and explanations for, genetic variation may be best pursued within more localized regions and defined time periods.
4Since at least the 1960s, characterizations of Andean peoples from a molecular perspective have been conducted peripherally, as part of larger investigative efforts in South America as a whole. These efforts have had two main goals: first, to inform debates on the peopling of South America and of the Americas writ large; second, to contribute to broad understandings of human micro-to macroevolutionary change. Both goals were vitalized by the work of James V. Neel, Francisco M. Salzano, and associated colleagues among tribal groups in Venezuela and Brazil. Thus, from the 1960s into the ...
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