The evolutionary significance of copy number variation in the human genome

Copy number variation provides the raw material for gene family expansion and diversification, which is an important evolutionary force. Moreover, copy number variants (CNVs) can influence gene transcriptional and translational levels and have been associated with complex disease susceptibility. Therefore, natural selection may have affected at least some of the greater than one thousand CNVs thus far discovered among the genomes of phenotypically normal humans. While identifying and understanding particular instances of natural selection may shed light on important aspects of human evolutionary history, our ability to analyze CNVs in traditional population genetic frameworks has been limited. However, progress has been made by adapting some of these frameworks for use with copy number data. Moving forward, these efforts will be aided by non-human organism studies of the population genetics of copy number variation, and by more direct comparisons of within-species copy number variation and between-species copy number fixation.