secondary sexual characteristic

External feature of an organism that is indicative of its gender (male or female), but not the reproductive organs themselves. They include facial hair in men and breasts in women, combs in cockerels, brightly coloured plumage in many male birds, and manes in male lions. In many cases, they are involved in displays and contests for mates and have evolved by sexual selection. Their development is stimulated by sex hormones – in humans the change in concentrations of these hormones at puberty results not only in the development of the physical secondary sexual characteristics, but also emotional changes.

In humans the development of secondary sexual characteristics is stimulated at puberty by the hormone oestrogen in women and testosterone in men. Testosterone is produced in the testes of males, while oestrogen and progesterone are produced in the ovaries of females. Women develop breasts and wider hips; men develop a deeper voice, body and facial hair, and stronger body odour; and both develop hair in underarm and genital regions. However, at puberty the reproductive organs also mature as a consequence of growth and changes in circulating hormones, ready for sexual reproduction.