Schrider Daniel R, Kern Andrew D
Department of Genetics, Rutgers University, Piscataway, NJ.
Human Genetics Institute of New Jersey, Rutgers University, Piscataway, NJ.
Mol Biol Evol. 2017 Aug 1;34(8):1863-1877. doi: 10.1093/molbev/msx154.
The degree to which adaptation in recent human evolution shapes genetic variation remains controversial. This is in part due to the limited evidence in humans for classic "hard selective sweeps", wherein a novel beneficial mutation rapidly sweeps through a population to fixation. However, positive selection may often proceed via "soft sweeps" acting on mutations already present within a population. Here, we examine recent positive selection across six human populations using a powerful machine learning approach that is sensitive to both hard and soft sweeps. We found evidence that soft sweeps are widespread and account for the vast majority of recent human adaptation. Surprisingly, our results also suggest that linked positive selection affects patterns of variation across much of the genome, and may increase the frequencies of deleterious mutations. Our results also reveal insights into the role of sexual selection, cancer risk, and central nervous system development in recent human evolution.
在近期人类进化中，适应性对基因变异的塑造程度仍存在争议。部分原因在于，人类中经典的“硬选择性清除”证据有限，即在这种情况下，一个新的有益突变迅速在种群中传播并固定下来。然而，正选择通常可能通过作用于种群中已存在的突变的“软清除”来进行。在此，我们使用一种对硬清除和软清除都敏感的强大机器学习方法，研究了六个人类群体中的近期正选择。我们发现有证据表明软清除广泛存在，并且占近期人类适应性的绝大部分。令人惊讶的是，我们的结果还表明，连锁正选择会影响基因组大部分区域的变异模式，并且可能增加有害突变的频率。我们的结果还揭示了性选择、癌症风险和中枢神经系统发育在近期人类进化中的作用。
