Authors contributed equally.
The molecular signature of selection underlying human adaptations
Article first published online: 13 NOV 2006
Copyright © 2006 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Supplement: Yearbook of Physical Anthropology
Volume 131, Issue Supplement 43, pages 89–130, December 2006
How to Cite
Harris, E. E. and Meyer, D. (2006), The molecular signature of selection underlying human adaptations. Am. J. Phys. Anthropol., 131: 89–130. doi: 10.1002/ajpa.20518
Authors contributed equally.
- Issue published online: 13 NOV 2006
- Article first published online: 13 NOV 2006
- Fundação de Amparo à Pesquisa do Estado de São Paulo (Brazil). Grant Number: 03/01583-8
- PSC-CUNY Award from the City University of New York
- positive selection;
- lactase persistence;
- skin color;
- natural selection
In the last decade, advances in human population genetics and comparative genomics have resulted in important contributions to our understanding of human genetic diversity and genetic adaptation. For the first time, we are able to reliably detect the signature of natural selection from patterns of DNA polymorphism. Identifying the effects of natural selection in this way provides a crucial piece of evidence needed to support hypotheses of human adaptation. This review provides a detailed description of the theory and analytical approaches used to detect signatures of natural selection in the human genome. We discuss these methods in relation to four classic human traits—skin color, the Duffy blood group, bitter-taste sensation, and lactase persistence. By highlighting these four traits we are able to discuss the ways in which analyses of DNA polymorphism can lead to inferences regarding past histories of selection. Specifically, we can infer the importance of specific regimes of selection (i.e. directional selection, balancing selection, and purifying selection) in the evolution of a trait because these different types of selection leave different patterns of DNA polymorphism. In addition, we demonstrate how these types of data can be used to estimate the time frame in which selection operated on a trait. As the field has advanced, a general issue that has come to the forefront is how specific demographic events in human history, such as population expansions, bottlenecks, and subdivision of populations, have also left a signature across the genome that can interfere with our detection of the footprint of selection at particular genes. Therefore, we discuss this general problem with respect to the four traits reviewed here, and describe the ways in which the signature of selection can be teased from a background signature of demographic history. Finally, we move from a discussion of analyses of selection motivated by a “candidate-gene” approach, in which a priori information led to the analysis of specific gene, to discussion of “genome-scanning” approaches that are directed at discovering new genes that have been under positive selection. Such scans can be designed to detect those genes that have been positively selected in our divergence from chimpanzees, as well as those genes that have been under selection as human populations have migrated, differentiated, and adapted to specific geographic environments. We predict that both approaches will be applied in the future, enabling a greater insight into human species-wide adaptations, as well as the specific adaptations of human populations. Yrbk Phys Anthropol 49:89–130, 2006. © 2006 Wiley-Liss, Inc.