Abstract
Numerous studies of human populations in Europe and Asia have revealed a concordance between their extant genetic structure and the prevailing regional pattern of geography and language. For native South Americans, however, such evidence has been lacking so far. Therefore, we examined the relationship between Y-chromosomal genotype on the one hand, and male geographic origin and linguistic affiliation on the other, in the largest study of South American natives to date in terms of sampled individuals and populations. A total of 1,011 individuals, representing 50 tribal populations from 81 settlements, were genotyped for up to 17 short tandem repeat (STR) markers and 16 single nucleotide polymorphisms (Y-SNPs), the latter resolving phylogenetic lineages Q and C. Virtually no structure became apparent for the extant Y-chromosomal genetic variation of South American males that could sensibly be related to their inter-tribal geographic and linguistic relationships. This continent-wide decoupling is consistent with a rapid peopling of the continent followed by long periods of isolation in small groups. Furthermore, for the first time, we identified a distinct geographical cluster of Y-SNP lineages C-M217 (C3*) in South America. Such haplotypes are virtually absent from North and Central America, but occur at high frequency in Asia. Together with the locally confined Y-STR autocorrelation observed in our study as a whole, the available data therefore suggest a late introduction of C3* into South America no more than 6,000 years ago, perhaps via coastal or trans-Pacific routes. Extensive simulations revealed that the observed lack of haplogroup C3* among extant North and Central American natives is only compatible with low levels of migration between the ancestor populations of C3* carriers and non-carriers. In summary, our data highlight the fact that a pronounced correlation between genetic and geographic/cultural structure can only be expected under very specific conditions, most of which are likely not to have been met by the ancestors of native South Americans.
Highlights
The way a certain habitat is first colonized by humans creates a primordial pattern of genetic variation that is subsequently attenuated by various demographic processes, including migration, population bottlenecks, fissions and fusions
A popular ramification of this paradigm is that most changes of the original genetic ‘make-up’ of a particular region follow trajectories established by geography and language [1] because, in addition to climatic conditions, the latter are the main conductors of gene flow
An analysis of molecular variance (AMOVA) of Y-short tandem repeat (STR) identified clearly distinguishable sub-clusters of western and eastern European Y chromosomes that were largely congruent with the Slavic and Romance language domains [7,9,11], and Y-chromosomal genetic discontinuities throughout the continent were found to coincide with linguistic boundaries [7,14,15,16]
Summary
The way a certain habitat is first colonized by humans creates a primordial pattern of genetic variation that is subsequently attenuated by various demographic processes, including migration, population bottlenecks, fissions and fusions. The type and degree of correlation observed between the genetic structure of an extant population on the one hand, and its linguistic and geographical structure on the other, should provide valuable information about the history of that population Dissenting processes such as the adoption of a new language without substantial gene flow into the adopting population, for example, by ‘elite dominance’ are usually conceived as exceptions to the rule [2]. Following this line of arguments, any concordance between genetic, linguistic and geographic data should be indicative of steady settlement, isolation by distance and constant population growth whereas discordances suggest abrupt demographic changes such as major contractions or relocations [3]. The correlation between genetics, language and geography may vary, across a highly differentiated region such as Europe, depending upon the local effective population size and the time-depth of the DNA markers used
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