Testosterone, which induces sexual differentiation of the male fetus, is believed to transfer from males to their littermates in placental mammals. Among humans, individuals with a male twin have been found to exhibit greater masculinization of sexually dimorphic attributes relative to those...

Testosterone, which induces sexual differentiation of the male fetus, is believed to transfer from males to their littermates in placental mammals. Among humans, individuals with a male twin have been found to exhibit greater masculinization of sexually dimorphic attributes relative to those...

Testosterone, which induces sexual differentiation of the male fetus, is believed to transfer from males to their littermates in placental mammals. Among humans, individuals with a male twin have been found to exhibit greater masculinization of sexually dimorphic attributes relative to those...

Testosterone, which induces sexual differentiation of the male fetus, is believed to transfer from males to their littermates in placental mammals. Among humans, individuals with a male twin have been found to exhibit greater masculinization of sexually dimorphic attributes relative to those...