Although this study did not find evidence for a statistically significant association between selection intensity (ω) in MCPH1, a gene associated with microcephaly, and absolute or relative brain size in cetaceans (Table 3), some intriguing patterns emerged from detailed phylogenetic and molecular analyses of MCPH1. Evolutionary models that included parameters for positive selection consistently fit the MCPH1 sequence data significantly better than alternative models of negative selection and neutral change (Table 1). Here, MCPH1 is linked to microcephaly.