The find indicates that species diversity two million years ago was “much smaller than presumed thus far,” the university said in a news release.

And it shows that diversity within the first global species of human, Homo erectus, “was as great as in humans today”.

The skull is the fifth to be found in Dmanisi, Georgia, following the recovery there of four other well-preserved skulls from the same period.

It was unearthed by anthropologists from the University of Zurich collaborating with Georgian colleagues under a project funded by the Swiss National Science Foundation and the Swiss Agency for Development and Cooperation.

The latest find, known as Dmanisi Skull 5, “has the largest face, the most massively built jaw and teeth and the smallest brain within the . . . group”.

The reason why Skull 5 is so important is that it unites features that have been used previously as an argument for defining different African “species”, university anthropologist Christoph Zollikofer says.

“Had the brain-case and the face of the Dmanisi sample been found as separate fossils, they very probably would have been attributed to two different species,” Zollikofer says in a statement.

“It is also decisive that we have five well-preserved individuals in Dmanisi whom we know to have lived in the same place and at the same time.”

Comparisons of the Dmanisi skulls with modern human and chimpanzee populations show that they belong to the same early species of man, Zollikofer said.

The five skulls are conspicuously different from each other “but not more different” than any five modern human or chimpanzee individuals from a given population, the scientists concluded.

Their research shows that “diversity within a species is thus the rule rather than the exception”.

The findings are to be published in the October 18th edition of the academic journal Science.