The Transylvanian Naked Neck Chicken

Research into why Transylvanian naked neck chickens have naked necks reveals a complex balance between genes and chemicals that produce a bird's (not just chickens) feather pattern while it is still an embryo in an egg. Once the combination was discovered, Chunyan Mou from the University of Edinburgh found that bird necks are naturally more disposed to nakedness than the rest of their bodies. This may be no benefit to poultry, but chickens are related to birds that do benefit.

Mou thinks that similar genetic tweaks have happened time and again in the evolution of birds. Many groups have lost their neck feathers independently, including vultures, the marabou stork, and large flightless birds like ostriches and emus. Naked necks allow vultures to stuff their heads into carcasses without soiling any feathers; in other cases, a naked neck probably helps its owner to keep cool in hot climates.

Whatever the benefit, it seems that it’s particularly easy for birds to evolve a naked neck, rather than another part of their body. After all, Mou found that the necks of embryonic ducks, turkeys, quails and guinea fowl all have much higher levels of retinoic acid than the rest of the body. This pattern would normally be innocuous, completely hidden from natural selection. But it allows BMP-boosting mutations to denude the neck in one fell swoop, while keeping the rest of the body covered in feathers. As Mou writes, “An underlying map within the skin provides a one-step route to a bare neck.”

The post goes into detail about how the genes initiate the production of chemical activators and inhibitors, and ends with a parable from Alan Turing that explains the concept in layman's terms. Link

(Image credit: Demontux)