Speciation and inversions: chimps and humans

A new set of models has resurrected a role for chromosomal inversions in the formation of new species. ((1-3)) Traditional models, which are generally considered to be unlikely in most cases, had imagined that inversions might aid speciation by directly causing low hybrid fitness. In contrast, the newer models focus on the effect that inversions have on local recombination rates. A test of these models found a strikingly high rate of amino-acid substitution within regions where humans and chimpanzees differ by inversions, suggesting perhaps that our ancestral species underwent a divergence process in which gene flow and inversions played a key role. ((4)) However, it remains uncertain whether this interesting finding is actually consistent with the proposed model. (C) 2003 Wiley Periodicals, Inc.