OVER the centuries, humanity has been impressed by the splendour of the peacock’s colours. Now physicists in China have discovered the secret of the peacock’s hues. In a study published this month in The Proceedings of the National Academy of Sciences, researchers report that slight variations in the arrangement of keratin and melanin are responsible for the palette of colours found in the eye of a peacock’s tail feather. (Keratin is the material also found in human fingernails; melanin is the substance that darkens human skin.) “It’s an ingenious and simple way to diversify colours,” said Dr Jian Zi, a physicist at Fudan University in Shanghai and lead author on the paper. He began the study with colleagues after being struck by the sight of peacock feathers in a Chinese market. “I study optics,” Zi said. “So when I looked at these peacock feathers against the sunshine, it was a fascinating experience. What can produce such diversified colours?” In peacocks, each feather has a central rigid stem lined on both sides by a row of smaller barbs. Each barb is then lined on both sides by rows of even tinier barbules. When scientists examined the barbules with a high-powered electron microscope, they saw that the barbules had, as an outer covering, a very regular structure built of tiny rods of melanin connected by keratin. Zi said they were not the first physicists to be entranced. Sir Isaac Newton suggested some 300 years ago that the peacock colours might be caused by structural colouration. The New York Times News Service
