"In response to the call for a human genome–evolution project (McConkey and Goodman 1997), the view has been expressed that what makes us human resides in the 1.5% difference in genomic DNA that separates us from chimpanzees (Gibbons 1998). This view is far too narrow. Features that we associate with being human did not just arise de novo in the past 6 million years since the lineage to humans separated from that to chimpanzees. Rather, some of the most striking human features, such as greatly enlarged brains and prolonged childhoods in social nurturing societies, have deep roots in our evolutionary history. Forty to 30 million years ago(Ma) neocortical portions of the brain increased in the two emerging branches of anthropoid primates—the platyrrhines (or New World monkeys) and the catarrhines. Within the catarrhine branch, additional marked enlargements occurred by 18–6 Ma in the lineage to the ancestors of modern hominids, and the largest neocortical increases occurred in the past 3 million years in the lineage to modern humans. A parallel evolutionary trend prolonged fetal life and the periods of postnatal life needed to reach full maturity. We may surmise that the genetic program for our enlarged neocortex has both ancient conserved features and more-recently derived features—in particular, the anthropoid-specific features shared with New and Old World monkeys and apes, the hominid-specific features shared with apes, and some human-specific features. Although many mutations in the past 40 million years have shaped the neurogenetic program for an enlarged neo-cortex, it is possible that just a small number of regulatory mutations in the past 6 million years have brought about the final enlargement of our neocortex compared with that of chimpanzees. Behaviorally, the separation between chimpanzees and humans is much smaller than once thought. Chimpanzees are emotionally complex and intelligent. They use tools and have material cultures (McGrew 1992), are ecological generalists, are highly social (De Waal 1995; McGrew et al. 1997), and apparently can learn and use rudimentary forms of language (Savage-Rumbaugh and Lewin 1994; Fouts 1997). In agreement with the newer information on the social lives and intelligence of chimpanzees and other apes (McGrew et al. 1997), the results of molecular studies of primate phylogeny (Goodman et al. 1998, and in press) challenge the traditional anthropocentric view that humans are very different from all other animals. Rather, the molecular results reveal that genetically we humans are only slightly remodeled apes. We share with our most distant living ape relatives (the gibbons and siamangs) 95% identity in genomic DNA, and with our closest relatives (the chimpanzees and bonobos, or pygmy chimpanzees) 98.3% identity in typical noncoding DNA and probably 99.5% identity in the active coding sequences of functional nuclear genes."