Many biologists have thought that "hair is an evolutionary innovation that occurred only in mammals," said Eckhart. Previous studies failed to show genes coding for hair keratin in chickens and other non-mammals. However, Eckhart's team showed that the one major component of hair -- cystein-rich alpha keratin -- is also expressed in the claw of the green anole lizard, suggesting these structures appear much earlier. The findings imply that there were several "steps in the evolution of hair," said Eckhart. "The first step, is the evolution of these keratins." Some researchers, however, are unconvinced by the novelty of this paper's findings. While the study adds to existing evidence that keratins are an important evolutionary stepping stone in the development of hair, that proposal is not new, Dominique Homberger from Louisiana State University wrote in an Email to __The Scientist.__ Also, she added, the evolutionary link between hair and claws isn't clear from the work. "It may be that similar keratin proteins are found in hard-cornified portions of hair and claws," she wrote, "but this does not mean that hair evolved from claws." __Image courtesy of Karin Jaeger and Leopold Eckhart, Medical University of Vienna__
Regularly taking breaks from eating—for hours or days—can trigger changes both expected, such as in metabolic dynamics and inflammation, and surprising, as in immune system function and cancer progression.