Neoteny (also called juvenilization, is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny is found in modern humans compared to other primates.

Human evolution's trend toward neoteny may have been caused by sexual selection in human evolution for neotenous facial traits in women by men with the resulting neoteny in male faces being a "by-product" of sexual selection for neotenous female faces.

An infant's face characteristically has features which distinguish it from a mature face. Picturing a baby's face, a layperson can probably readily call to mind a number of the aspects which have been identified by researchers as typical of infants.

These “neotenous” characteristics include a large forehead with lower set eyes, nose and mouth; a smaller, shorter, more recessive chin; fuller lips; larger eyes; a smaller nose; higher, thinner eyebrows; and a rounder, less angular face.

The presence of babyface features has been correlated with attractiveness for both females and males, although the effect is more consistent and larger for females, and is curvilinear (increasing, and then at a point, reducing attractiveness) for males.

Adult females tend to retain more neoteny than male faces and as such babyfaceness is to a degree definitional of facial feminity.