A research team of Chinese and American paleontologists suggest that the giant pandas' dedicated bamboo diet originated at least six million years ago. This finding was based on an analysis of a fossil of an Ailurarctos – an extinct ancestor of the modern panda – unearthed from Shuitangba in southwest China's Yunnan Province. The fossil is the earliest example of an enlarged radial sesamoid – a bone that functions as an opposable thumb – in the panda's lineage, which pandas use to manipulate bamboo. The site dates back to the late Miocene period, or about six to seven million years ago. The results have been published in Science Reports, an influential academic journal.