Evo-Devo Sheds Light on Mechanisms of Human Evolution: Limb Proportions and Penile Spines

Evolutionary developmental anthropology takes advantage of a broad range of phenotypic, genetic, and embryological analyses to identify the genomic and developmental mechanisms underlying the intraspecific variation and evolutionary diversity of human and primate anatomy. Developmental processes, such as outgrowth, typically involve the interaction of separate cell populations dedicated to mitosis verses organization, the limb bud zone of polarizing activity (ZPA) and apical ectodermal ridge (AER) and the growth plate reserve zone and perichondrium. This chapter describes two approaches that have helped to identify particular developmental and genetic mechanisms underlying human evolution. It addresses the hypothesis that evolutionary differences in forelimb skeletal proportions correspond to Hox modules. The rapidly expanding knowledge and methodologies related to the mechanisms of Hox regulation of target genes in the tetrapod limb, human and primate genomic variation, and computational tools available for identifying species-specific variants provide hope that such evolutionarily relevant changes will soon be identified.