"The textbook wisdom about the wild origins of the 860 million chickens eaten each year in Britain is overturned today.

Since the days of Charles Darwin, scientists have maintained that the domesticated chicken derives from the red jungle fowl, which was first raised in captivity in Asia five millennia ago.

But an in depth study of chicken legs has overturned this idea, revealing that the origins of this bird are much more complicated.

The genetic study has revealed why foods like corn give chickens yellow legs, demonstrating that though the great Darwin was right about many things, his view on the origins of the chicken was not entirely correct.

The study, published in the open-access journal PLoS Genetics, reveals the DNA variant that is responsible for yellow skin in billions of chickens raised worldwide.

The problem came when the researchers looked for the yellow-skin gene in the red junglefowl. They only found the genetic variant that codes for white skin.

More surprisingly, when they looked at the identical stretch of DNA in wild species such as red, grey, green, and Ceylon junglefowl they discovered that the sequence found in grey junglefowl was closest to yellow-skinned domestic chickens.

This discovery indicates that though chickens are indeed primarily derived from red junglefowls, at some point after chickens were first domesticated, they interbred with grey junglefowls which resulted in the incorporation of the gene that turned their legs a pleasing yellow colour.

Dr Greger Larson, who works at Uppsala University and at Durham University, says: "Darwin recognised the importance of studying domestic animals as a model of evolution and this insight has proved enormously influential.

"The ironic thing is that he believed that dogs were hybrids of several wild ancestors but that chickens only had one, and he was wrong on both counts." (Dogs are descended solely from the grey wolf.)

Yellow colouring comes from pigments found in feed called carotenoids: the more of these pigments, the more yellow the legs. The gene in question codes for an enzyme that degrades carotenoids into a colourless form, releasing Vitamin A.

But while white-skinned chickens make this enzyme in skin, yellow-skinned chickens do not, allowing the carotenoids to accumulate and produce yellow colouring. Interestingly, the gene functions normally in other tissues, so it is only their legs that go saffron yellow.

"This is a beautiful demonstration of how important regulatory mutations are for evolutionary changes" says Prof Leif Andersson, leader of the research team that includes Jonas Eriksson.

"What we are interested in knowing now is why yellow skin in chickens is so ubiquitous. It could have been that yellow skin was perceived to be a marker of health or size or egg production, or it could just be that yellow skin was fun to look at.

"We're really not sure. Furthermore, the gene we have identified may be important for carotenoid-based pigmentation in other species like the pink colour of the flamingo; the yellow legs of many birds of prey including eagles, falcons and hawks; the pink muscles of salmon, and even skin colour in humans."

The study was funded by the European Molecular Biology Organization, the Swedish Foundation for Strategic Research, Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning and the Swedish Research Council."

Source:http://www.telegraph.co.uk/earth/mai...chicken129.xml

I was watching this show on Discovery that showed that birds originated from the dinosaurs, and they actually learned how to turn off and on certain genes to induce the growth of teeth, scales, and other characteristics of dinosaurs that are stored in the genome of birds.