An international team of researchers using sophisticated x-ray technology has found chemical traces of a key color pigment in 100-million year old fossilized birds that once formed their feather patterns. The study, reported Thursday in the journal Science, provides a glimpse into the biochemistry of prehistoric animals and greater understanding of their diets and environment. Working at Stanford University\'s National Accelerator Laboratory in California, the author\'s discovered chemical traces of a pigment, known as eumelanin, that is one of the coloring agents responsible for brown eyes and dark hair in many modern species, including humans. \"This is a pigment that evolved a very, very long time ago, but is still actively synthesized by organisms on the planet,\" said geochemist Roy Wogelius of the University of Manchester, one of the leaders of an international team that reported the discovery. \"We found a way to map it and show its presence over 120 million years of geological time passing,\" he said. \"It is a direct relationship between you, me, and some extremely old organisms.\" Using synchrotron radiation, the researchers examined two fossilized birds, Confuciusornis sanctus, which lived 120 million years ago, and had the first known bird-like beak, and Gansus yumenensis, considered the oldest modern bird, which lived more than 100 million years ago and looked a bit like a modern grebe, a type of freshwater diving bird.