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Contributed by Francisco Mauro Salzano, January 2, 2017 (sent for review July 5, 2016; reviewed by Theodore G. Schurr and Anne C. Stone)
Significance
There is much interest in understanding the role of natural selection in shaping physiological adaptations to climate, diet, and diseases in humans. We investigated this issue by analyzing genomic data from Native American populations inhabiting different ecological regions and ancient Native Americans. We found signals of natural selection at the fatty acid desaturases (FADS) genes not only in an Arctic population, as was previously found, but throughout the Americas, suggesting a single and strong adaptive event that occurred in Beringia, before the range expansion of the first Americans within the American continent and Greenland.
Abstract
When humans moved from Asia toward the Americas over 18,000 y ago and eventually peopled the New World they encountered a new environment with extreme climate conditions and distinct dietary resources. These environmental and dietary pressures may have led to instances of genetic adaptation with the potential to influence the phenotypic variation in extant Native American populations. An example of such an event is the evolution of the fatty acid desaturases (FADS) genes, which have been claimed to harbor signals of positive selection in Inuit populations due to adaptation to the cold Greenland Arctic climate and to a protein-rich diet. Because there was evidence of intercontinental variation in this genetic region, with indications of positive selection for its variants, we decided to compare the Inuit findings with other Native American data. Here, we use several lines of evidence to show that the signal of FADS-positive selection is not restricted to the Arctic but instead is broadly observed throughout the Americas. The shared signature of selection among populations living in such a diverse range of environments is likely due to a single and strong instance of local adaptation that took place in the common ancestral population before their entrance into the New World. These first Americans peopled the whole continent and spread this adaptive variant across a diverse set of environments.
Footnotes
↵1C.E.G.A. and K.N. contributed equally to this work.
- ↵2To whom correspondence may be addressed. Email: francisco.salzano{at}ufrgs.br or hunemeier{at}usp.br.
Author contributions: C.E.G.A., K.N., and T.H. designed research; C.E.G.A., K.N., and T.H. performed research; C.E.G.A., K.N., and T.H. analyzed data; and C.E.G.A., K.N., D.M., D.C., M.C.B., F.M.S., and T.H. wrote the paper.
Reviewers: T.G.S., University of Pennsylvania; and A.C.S., Arizona State University.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1620541114/-/DCSupplemental.
Natural selection in first Americans
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