The Evolutionary Trajectory of Primate Skin Appendage Traits

The study investigated the evolutionary development of human skin traits by examining hair follicle and eccrine sweat gland densities in macaques, chimpanzees, and humans. It found that while humans have a hair density similar to chimpanzees, it is significantly lower than that of macaques. However, humans have a 10-fold higher density of eccrine sweat glands compared to both chimpanzees and macaques, which have similar densities. These findings suggested that the evolutionary path involved a decrease in hair density in the ancestors of humans and apes, followed by an increase in eccrine gland density and a reduction in fur cover unique to humans. This research provided insights into the distinctiveness of human skin and proposed a revised evolutionary model for these traits.