Biological females may undergo vaginectomy, while males may undergo penectomy.

Earlier studies had shown that males of both species underwent hormonal changes when their mates were pregnant.

Women lack the same neuromuscular spurt that males undergo during puberty.

Not all males undergo circumcision.

"We don't know if males undergo a period when they don't eat," Dr. Hueter said.

The Sambia are unique in that they require males to undergo three specific sexual phases in their lives.

In one study, 10 adult males underwent positron emission tomography scans in three different scenarios:

In males previously having undergone radiotherapy, there appears to be no increase in genetic defects or congenital malformations in their children conceived after therapy.

Hair from 700 Taiji residents were tested for mercury; 117 males and 77 females who showed over 10 ppm underwent further neurological tests.

Paternal males do not undergo these same hormonal changes and so the proximate causes of the onset of parental behaviors must differ from those in females.