Secondary sex characteristics are those characteristics we associate with male and female characteristics after the onset of puberty. After the primary characteristics of egg or sperm production, secondary characteristics develop as a result of the male and female sex hormones testosterone and estrogen, respectively. In males, the secondary characteristics include a deeper voice, body and facial hair, a bigger size and growth of the sex organs. In females, a larger hip area(for later childbearing), breast development, pubic hair, menses, a larger uterus and feminine body shape. In most animals where there are males and females, secondary sex characteristics may provide a selective advantage for mating. Male peacock feathers that are displayed as part of a courtship ritual are an example. Male lions have an impressive mane. These can help attract females to males to insure reproduction occurs.