Photos

human female breasts.
Breastfeeding.
Breasts at 6 months pregnantThe function of the mammary glands in female breasts is to nurture the young by producing milk, which is secreted by the nipples during lactation. While the mammary glands that produce milk are present in the male, they normally remain undeveloped. The orb-like shape of breasts may help limit heat loss, as a fairly high temperature is required for the production of milk.

Milk production can also occur in both men and women as an adverse effect of some medicinal drugs (such as some antipsychotic medication), extreme physical stress or in endocrine disorders. Often, newborn babies are capable of lactation because they receive some amount of prolactin and oxytocin (milk hormones) from their connection to the mother.

Although the secretion of milk is the function of the mammary glands, these actually make up a relatively small fraction of the overall breast tissue. It is commonly assumed by biologists that the real evolutionary purpose of women having breasts is to attract the male of the species; that, in other words, breasts are sexually dimorphic, or secondary sex characteristics.

Others believe that the human breast evolved in order to prevent infants from suffocating while feeding[2]. Since human infants do not have a protruding jaw like our ancestors and the other primates, the infant's nose might be blocked by a flat female chest while feeding. According to this theory, as the human jaw became recessed, the breasts became larger to compensate.