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Cover Mother (Miff) and daughter (Moeza, ∼1 year old) chimpanzees (Pan troglodytes) from the Gombe National Park, Tanzania, 1970. (For more information on the chimpanzee community at Gombe National Park, see www.discoverchimpanzees.org or www.janegoodall.org.) In this issue, array comparative genomic hybridization is used to generate the first comprehensive genome-wide map of copy number variation (CNV) in humans and chimpanzees. Population genetic analyses comparing the rates of copy number fixation and variation identified specific genes that may have played important roles in the adaptive phenotypic differentiation of humans and chimpanzees. (Photo copyright: Leanne T. Nash. [For details, see Perry et al., pp. 1698-1710.])