section_path: Biology
section_name: Biology
paragraph_text: Biology
  
  In humans, sperm cells carry either an X or a Y sex chromosome. If a sperm cell carrying a Y chromosome fertilizes the female ovum, the offspring will have a male karyotype (XY). The SRY gene is typically found on the Y chromosome and causes the development of the testes, which in turn govern other aspects of male sex differentiation. Sex differentiation in males proceeds in a testes-dependent way while female differentiation is not gonad dependent.
  
  Primary sex characteristics (or sex organs) are characteristics that are present at birth and are integral to the reproductive process. For men, primary sex characteristics include the penis and testicles.
  
  Adult humans exhibit sexual dimorphism in many other characteristics, many of which have no direct link to reproductive ability. Humans are sexually dimorphic in body size, body structure, and body composition. Men tend to be taller and heavier than women, and adjusted for height, men tend to have greater lean and bone mass than women, and lower fat mass.
  
  Secondary sex characteristics are features that appear during puberty in humans. Such features are especially evident in the sexually dimorphic phenotypic traits that distinguish between the sexes, but—unlike the primary sex characteristics—are not directly part of the reproductive system. Secondary sexual characteristics that are specific to men include:
  
  Men weigh more than women. On average, men are taller than women by about 10%. On average, men have a larger waist in comparison to their hips (see waist–hip ratio) than women. In women, the index and ring fingers tend to be either more similar in size or their index finger is slightly longer than their ring finger, whereas men's ring finger tends to be longer.