Joined: Jan. 2006
Yes, effective population sizes have been far higher in apes than in our lineage. That alone could explain why we are less polymorphic.
See this study :
Nature Genetics 27, 155 - 156 (2001)
Great ape DNA sequences reveal a reduced diversity and an expansion in humans
|The extent of DNA sequence variation of chimpanzees is several-fold greater than that of humans1. It is unclear, however, if humans or chimpanzees are exceptional among primates in having low and high amounts of DNA sequence diversity, respectively. To address this, we have determined approximately 10,000 bp of noncoding DNA sequences at Xq13.3 (which has been extensively studied in both humans and chimpanzees1, 2) from 10 western lowland gorillas (Gorilla gorilla gorilla) and 1 mountain gorilla (Gorilla gorilla beringei; that is, from 2 of the 3 currently recognized gorilla subspecies3), as well as 8 Bornean (Pongo pygmaeus pygmaeus) and 6 Sumatran (Pongo pygmaeus abelii) orang-utans, representing both currently recognized orang-utan subspecies4. We show that humans differ from the great apes in having a low level of genetic variation and a signal of population expansion.|