Hawks John, Wang Eric T, Cochran Gregory M, Harpending Henry C, Moyzis Robert K
Department of Anthropology, University of Wisconsin, Madison, WI 53706, USA.
Proc Natl Acad Sci U S A. 2007 Dec 26;104(52):20753-8. doi: 10.1073/pnas.0707650104. Epub 2007 Dec 17.
Genomic surveys in humans identify a large amount of recent positive selection. Using the 3.9-million HapMap SNP dataset, we found that selection has accelerated greatly during the last 40,000 years. We tested the null hypothesis that the observed age distribution of recent positively selected linkage blocks is consistent with a constant rate of adaptive substitution during human evolution. We show that a constant rate high enough to explain the number of recently selected variants would predict (i) site heterozygosity at least 10-fold lower than is observed in humans, (ii) a strong relationship of heterozygosity and local recombination rate, which is not observed in humans, (iii) an implausibly high number of adaptive substitutions between humans and chimpanzees, and (iv) nearly 100 times the observed number of high-frequency linkage disequilibrium blocks. Larger populations generate more new selected mutations, and we show the consistency of the observed data with the historical pattern of human population growth. We consider human demographic growth to be linked with past changes in human cultures and ecologies. Both processes have contributed to the extraordinarily rapid recent genetic evolution of our species.
对人类的基因组调查发现了大量近期的正选择现象。利用390万个HapMap单核苷酸多态性（SNP）数据集，我们发现，在过去4万年里选择作用大大加速。我们检验了一个零假设，即观察到的近期受到正选择的连锁块的年龄分布与人类进化过程中适应性替代的恒定速率是一致的。我们表明，一个足以解释近期选择的变异数量的恒定速率会预测：（i）位点杂合度比在人类中观察到的至少低10倍；（ii）杂合度与局部重组率之间有很强的关系，而这在人类中并未观察到；（iii）人类与黑猩猩之间存在数量高得难以置信的适应性替代；以及（iv）高频连锁不平衡块的数量几乎是观察到的数量的100倍。更大的群体产生更多新的被选择的突变，并且我们展示了观察到的数据与人类人口增长的历史模式的一致性。我们认为人类人口增长与过去人类文化和生态的变化有关。这两个过程都促成了我们这个物种近期异常快速的遗传进化。
