page_title: Secondary sex characteristic
hierarchical_section_title: Secondary sex characteristic
caption_attribution_description: English: Male Indian peafowl (Pavo cristatus) displaying Español: Cola del Pavo Real (Pavo cristatus) macho.
context_page_description: Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a species, but--unlike the sex organs--are not directly part of the reproductive system. Secondary sex characteristics are believed to be the product of sexual selection for traits which display fitness, giving an organism an advantage over its rivals in courtship and in aggressive interactions.
  Secondary sex characteristics include, for example, the manes of male lions, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes. These characteristics are believed to be produced by a positive feedback loop known as the Fisherian runaway produced by the secondary characteristic in one sex and the desire for that characteristic in the other sex. Male birds and fish of many species have brighter coloration or other external ornaments. Differences in size between sexes are also considered secondary sexual characteristics.
context_section_description: Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a species, but--unlike the sex organs (primary sex characteristics)--are not directly part of the reproductive system. Secondary sex characteristics are believed to be the product of sexual selection for traits which display fitness, giving an organism an advantage over its rivals in courtship and in aggressive interactions. 
  Secondary sex characteristics include, for example, the manes of male lions, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes. These characteristics are believed to be produced by a positive feedback loop known as the Fisherian runaway produced by the secondary characteristic in one sex and the desire for that characteristic in the other sex. Male birds and fish of many species have brighter coloration or other external ornaments. Differences in size between sexes are also considered secondary sexual characteristics.
  In humans, visible secondary sex characteristics include pubic hair, enlarged breasts and widened hips of females, and facial hair and Adam's apples on males.
caption: A peacock displays his long, colored tail, an example of secondary sex characteristics
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