Scientists solve half-cock chicken mystery

Researchers say they've solved the mystery of why some chickens hatch out half-male and half-female. About one in every 10,000 chickens is gynandromorphous, to use the technical term.

In medieval times, they might have been burned at the stake, as witches' familiars. But now these chickens are shedding important new light on how birds, and perhaps reptiles, develop.


The left, white, side of this bird is male. The right, brown, side is female.

It used to be thought that hormones instructed cells to develop in male or female-specific ways. That's what happens in mammals, including humans, and it leads to secondary sexual characteristics like facial hair for men or breasts for women.

But scientists at the Roslin Institute and the University of Edinburgh say they have discovered that bird cells don't need to be programmed by hormones. Instead they are inherently male or female, and remain so even if they end up mixed together in the same chicken. It means a half-and-half chicken will have totally different plumage, body shape, and muscle structure on the two halves of its body.

Full story here.