Secondary sex characteristics

Physical traits that distinguish the biological sexes of a species

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Secondary sex characteristics are features that appear during puberty in humans, and at sexual maturity in other animals. These characteristics are not directly involved in reproduction, unlike primary sex characteristics, which are the sex organs themselves. Secondary sex characteristics are the result of hormonal changes and are often used to distinguish between the sexes of a species.

Development

Secondary sex characteristics develop during puberty in response to increased levels of sex hormones. In humans, these hormones include testosterone in males and estrogen in females. The development of these characteristics is a key part of the puberty process.

In Males

In males, secondary sex characteristics include:

• Growth of facial and body hair, such as on the chest and back.
• Deepening of the voice due to the growth of the larynx.
• Increased muscle mass and strength.
• Broadening of the shoulders.
• Growth of the Adam's apple.

In Females

In females, secondary sex characteristics include:

• Development of breasts.
• Widening of the hips.
• Growth of pubic and underarm hair.
• Increased body fat distribution around the hips, thighs, and buttocks.

Function

Secondary sex characteristics play a role in sexual selection, as they can be used to attract mates. For example, the deep voice of a male or the breast development in females can be signals of reproductive maturity and health.

Hormonal Regulation

The development of secondary sex characteristics is regulated by the endocrine system. The pituitary gland releases hormones that stimulate the gonads to produce sex hormones. These hormones then act on various tissues in the body to bring about the changes associated with puberty.

Evolutionary Perspective

From an evolutionary standpoint, secondary sex characteristics may have developed to enhance reproductive success. They can serve as indicators of genetic fitness and health, thus influencing mate selection.

Also see

• Primary sex characteristics
• Puberty
• Sexual dimorphism
• Endocrine system
• Testosterone
• Estrogen