According to a study, the longer it takes a woman to get pregnant, the greater her chances of having a boy.
A female wasp stings a spider in her own web, temporarily paralyzing her. Then the wasp lays an egg on the spider’s abdomen. The paralysis wears off, and the spider gets up and goes about her business as usual.
There’s a common belief that men can sire children until they die, but that women need to be relatively young to conceive healthy children. But the father’s age affects the child’s health too.
Depo-provera is the brand name of a method of birth control that consists mostly of a hormone much like progesterone, a hormone that works with estrogen to regulate the menstrual cycle.
The female wood mouse has multiple mates, so the sperm of this wood mouse may be competing with sperm from other males.