Chicken Head Reverse Evolution

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Chicken head reverse evolution reported in New Scientist, 20 August 2011, p6. Arhat Abzhanov, an evolutionary biologist at Harvard University has developed a technique to reverse evolution in chickens so that they form a snout like an alligator, rather than a beak. Abzhanov has been studying the genes involved in forming the different shapes of Galapagos finch beaks and found that the different shapes were the result of variations in the activity of just a few genes brought about by changes in signalling molecules that turned the genes on and off. He suggested that the change from snout to beak may involve similar such changes in signalling molecules. The tip of an alligator snout is formed from a pair of bones which remain separate, but a bird beak forms into a single sharp bone. Abzhanov looked for signalling molecules in developing alligator and chicken embryos and found they had two in common, but their distribution was different. In alligators they were active on either side of the developing face, but not in the centre. In chickens they were active in the centre as well as the sides.

Abzhanov developed a method of blocking the activity of the signalling molecules using proteins embedded in tiny gel pellets. When he inserted these into the centre of five-day-old chicken embryos he found they developed a pair of bones just like an alligator embryo at the equivalent stage. According to Abzhanov this snout-like feature is something "modern birds have not seen since the Cretaceous". Due to ethics regulations on animal experiments the chickens that have been experimented on this way are not allowed to hatch.

Editorial Comment: Turning off the signalling molecules in the centre of the developing chicken face only messes up chicken heads by preventing them from growing a proper beak. The chicken embryos are still chickens, and if they were allowed to mature and hatch we predict they would turn out to be deformed chickens that would not survive any struggle for life. A similar failure of growth occurs in humans during the growth of the upper lip and palate. The upper lip is normally formed by tissue growing in from each side and fusing with tissue growing down into the centre. When the central part does not grow or join up with the sides the resulting deformity of the lip is called “hare lip”, because of its resemblance to the split upper lip in a hare, but no one would claim this as evidence humans are descended from hares.

The fact that alligators and chickens have some identical growth factors is no more significant than the fact mice and men have 75% similar DNA, and 75% of human genes are found in nematode worms, plus “We share half our genes with the banana.” (Robert May, UK chief Scientist, New Scientist, 1 July 2000), but none of this indicates we descended from them. The current theory of evolution claims that dinosaurs evolved into birds, but other important body structures such as their hip bones, are just as different from birds as their heads. Instead of wasting time trying to prove crocodile hipped dinosaurs evolved into birds, this research should be put to use to help us understand how growth defects occur and how we could fix them. (Ref. embryology, teratology, aves, reptiles)

Evidence News 31 August 2011

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