Scientists say an entirely separate type of human identified from bones in Siberia co-existed and interbred with our own species.The ancient humans have been dubbed "Denisovans" after the caves in Siberia where their remains were found. There is also evidence that this population was widespread in Eurasia. A study in Nature journal shows that Denisovans co-existed with Neanderthals and interbred with our species - perhaps around 50,000 years ago. An international group of researchers sequenced a complete genome from one of the ancient hominins (human-like creatures), based on nuclear DNA extracted from a finger bone.