Is 2-million-year-old African fossil the missing link in human evolution?

London, Apr 9 (ANI): Suggestions that the newly found hominin fossils in South Africa represent a transitional species in human evolution have created a furore among researchers.

A team from the University of the Witwatersrand in Johannesburg has revealed two remarkably well-preserved hominin fossils aged just under two million years old.

The fossils were discovered at Malapa cave, part of a site known as the Cradle of Humankind, some 40 kilometres west of Johannesburg, reports Nature.

The researchers have suggested that the fossils represent a transitional species in human evolution, sitting between Australopithecus and Homo species.

However, other researchers have said that the claims are overstated.

The fossils, a juvenile male and an adult female, were found together in the Malapa cave, part of an eroded cave system, leading to speculation that the two fell to their deaths while searching for water.

Controversially, the researchers have named the fossils as a new species, Australopithecus sediba.

'Sediba' means fountain or wellspring in Sotho, which is one of the 11 official languages of South Africa.

Berger deems this an appropriate name, as he says that A. sediba is a good candidate for being the transitional species between the southern African hominin, Australopithecus africanus, and early Homo species - either the earlier Homo habilis or even a direct ancestor of the more recent Homo erectus.

But palaeoanthropologist Tim White of the University of California, Berkeley, has said that A. sediba and A. africanus are merely chronospecies- names given to describe slightly different anatomy in fossils from a single evolving species.

White said that the suggestion by Berger and his team that this lineage split before the emergence of Homo is "fossil-free speculation", adding that "the obsession with Homo in their title and text is difficult to understand outside of a media context".

Anthropologist Fred Grine of Stony Brook University in New York says that the authors have "not undertaken any competent analysis of variation within A. africanus - something I do not understand in the context that three further skeletons have been found by the same team at Malapa".

He said that although Berger and his colleagues compare the A. sediba specimens to other hominins in terms of morphological characters that he and co-author Heather Smith defined in a paper two years ago, the team's analysis raises questions about the character states used and how they have been coded.

Both Grine and White are critical of the fact that most of the diagnosis of A. sediba is on the basis of a single immature individual, and point out that because anatomy changes during growth, the jury will be out until more complete adult remains are described.

Grine added that a further issue relates to the suggestion that A. sediba was ancestral to Homo.

As for the age of the specimens, Berger said that as this is the first time that fossils of A. sediba have been discovered, he and his colleagues have not established over what period of time the species existed.

"The site we have found is simply a point in time and does not in any way represent the first appearance of this species nor the last," he said.

The research is published in Science1,2. (ANI)