Melanin of the nipple areola complex.

Biological pigments or biochromes are ubiquitous in animals, plants, and simpler organisms such as fungi and bacteria. They serve a wide spectrum of functions from photosynthesis, camouflage, mimicry, photo protection from the environment to attracting mates. The human female nipple areola complex (NAC) is a highly-pigmented area. Currently, the prevailing theory as to the evolution of the pigmented human NAC is based on infant recognition of breast feeding latching zone; however, due to the protruding shape of the nipple and surrounding breast, the authors of this letter believe that the evolutionary advantage of the pigmented NAC has a direct physiological function, namely the initiation of involution at the end of the infant lactation period.