Secondary sex characteristic

Secondary sex characteristics are physical features that distinguish males and females of a species, but that are not directly part of the reproductive system. They are believed to be the product of sexual selection for traits which give an individual an advantage over its rivals in courtship and aggressive interactions. They are distinguished from primary sex characteristics, which are the sex organs.

In humans[edit]

In humans, visible secondary sex characteristics include pubic hair, enlarged breast tissue in females, and facial hair in males. They are one of the many physical changes associated with puberty. The development of secondary sex characteristics is regulated by sex hormones produced by the gonads (testes and ovaries) and the adrenal glands.

In other animals[edit]

In many other animals, secondary sex characteristics play a key role in signaling sexual maturity and fertility. Examples include the bright plumage of male birds, the manes of male lions, and the antlers of male deer.