Fig. 4.

A genetic basis for the evolution of increased eccrine gland density in human skin. ECE18 is a developmental enhancer of the anthropoid Engrailed 1 locus. Over the course of human evolution, the ECE18 enhancer accumulated multiple activity-enhancing single nucleotide mutations, particularly at the SP1 sites SP1^A and SP1^B (boxed and bold), that collectively induced the specification of more eccrine glands in human skin by potentiating developmental EN1 expression. Derived human substitutions relative to other apes underlying higher activity of hECE18 are in red.