Researchers say a fossil jawbone discovered in Taiwan belonged to an enigmatic group of early human ancestors. Relatively little is known about Denisovans, an extinct group of human cousins that interacted with Neanderthals and our own species, Homo sapiens. The probable identification expands the region where scientists know these ancient people once lived. At least three human ancestor groups coexisted in Eurasia and sometimes interbred. The findings were published Thursday in the journal Science. One independent expert says he would like to see further data before confirming the Taiwan fossil as Denisovan.