HOW old is Homo sapiens? Comparing the genomes of modern humans with those from fossils of Neanderthals (Homo neanderthalensis) suggests that the lines leading to these two species split from one another more than 500,000 years ago. But that does not answer the question of when they achieved their distinctive forms.
Fossils recognisable as Neanderthals go back 250,000 years, about halfway between the present day and the time of their common ancestor with Homo sapiens, a member of a species called Homo heidelbergensis. Several sites older than 250,000 years and containing fossils intermediate in form between heidelbergensis and neanderthalensis are known, making 250,000 years a reasonably definitive date.