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.

Until now, however, the most ancient bones universally agreed to have belonged to Homo sapiens have dated back only 195,000 years. And fossils intermediate in form between sapiens and heidelbergensis are scarce. How quickly the relevant branch of Homo heidelbergensis turned into something that could be called Homo sapiens was therefore obscure. But work led by researchers at the Max Planck Institute for Evolutionary Anthropology, in Leipzig, Germany, which has just been published in Nature, has shed some light. The remains of at least five individuals, collected from a site called Jebel Irhoud, in Morocco, look like modern humans and seem to date back 300,000 years. That not only makes them the oldest Homo sapiens found so far (and shows that sapiens is actually an older species than neanderthalensis). It also demonstrates that sapiens was far more widespread than researchers had suspected, for previous early fossils of the species have come exclusively from eastern and southern Africa.

The fossils themselves are described by a group led by Jean-Jacques Hublin. They include a cranium, a lower jaw bone, an upper jaw, and various other skull fragments and teeth. Adding these together and filling in the blanks yields a model of the creature’s skull (pictured), and comparing this with other fossils, some definitively identified as Homo sapiens and some equally definitively identified as not, shows that the parts from which it is composed come from a sapiens population.

The likely age of this population was worked out by Dr Hublin’s colleague Daniel Richter and his team (of which Dr Hublin was also a member). They used a technique called thermoluminescence to date stone tools found in the same stratum as the fossils. They also re-dated a tooth that had been found in a badly recorded excavation carried out on the same site in the 1960s. This tooth had been thought to be 160,000 years old, and thus not of such great interest. However, both tools and tooth proved, within the margins of error of the techniques involved, to be about 300,000 years old.