Scientists delight in ancient skull find

"It's a lot of emotion to have in my hand - the beginning of the human lineage," said Michel Brunet of the University of Poitiers, France.

"I have been looking for this for so long. I knew I would one day find it... I've been looking for 25 years," he told reporters in Chad.

Daniel Lieberman of Harvard University, US, one of Brunet's contemporaries to have seen the Chad skull, said its discovery would have the impact of "a small nuclear bomb".

And Henry Gee, senior editor at Nature, which carried full details of the find, had no doubts about its significance:

"Toumai is arguably the most important fossil discovery in living memory, rivalling the discovery of the first 'ape-man' 77 years ago - the find which effectively founded the modern science of palaeoanthropology," he said.

Professor Chris Stringer at the Natural History Museum in London, UK, said that the discovery of Toumai was "very significant".

"First, because of its location in what is now desert, over a thousand miles away from the sites in East Africa that have featured in the search for our origins so far.

"Second, because it is the only relatively complete skull so far discovered in a 'fossil gap' of five million years between the ancestral apes of nine million years ago and the australopithecines, generally regarded as our close relatives, from four million years onwards," he said.

Sahelanthropus tchadensis, to give Toumai its scientific name, had a mixture of features.

"It had an ape-like brain size and skull shape, combined with a more human-like face and teeth.

"It also sported a remarkably large brow-ridge, more like that of younger human species.

"Its discovery shows how much evidence has been missing up to now," Professor Stringer said.

The number of precursors of modern humans living at the time of Toumai might well be as high as the number of modern ape species alive today.

Researchers would be looking for gorilla and chimpanzee ancestors from Toumai's time, too, he added.