A team of scientists has uncovered the skeletal remains of an unknown species of ancient human, it was revealed today.
The researchers suggest the species - named Australopithecus sediba - could be a direct ancestor to Homo erectus, the predecessor of modern humans.
The two partial articulated skeletons of an adult female and child were found in miners' debris in South Africa in the Cradle of Humankind World Heritage Site in 2008 by Professor Lee Berger from South Africa's University of the Witwatersrand.
The fossils were dated as being around 1.95 million years old, placing the species at a transition point in our evolutionary story from small brained bipedal apes to larger brained human ancestors.
Dr Andy Herries, archaeological scientist from the School of Medical Sciences at the University of New South Wales, Australia, was part of the team which dated the remains.
He said the remains might not be the oldest at the site.
"Until recently it was impossible to get precise dates for the South African cave sites, but with the development of new techniques we are beginning to understand the relationships of the various species of early human to each other," he said.
"This is a period of major climatic change and increasing aridity in Africa, when a number of different species of potential early Homo ancestors occur, each adapting to these changes in different ways.
"Sediba appears to have traits of both the earlier species, Australopithecus africanus, and a later species, Homo erectus.
"It is likely that these fossils do not represent the oldest evidence for Au. sediba. Sediments older than two million years occur at the site and only time will tell if they will reveal earlier examples of Australopithecus sediba or other species of human ancestors."
His colleague Professor Paul Dirks, head of the School of Environmental Sciences at James Cook University, Australia, led the team which described the geological setting and age of the remains.
He said paleomagnetic analysis of the debris encasing the fossils had helped define their age.
"These ages coincide with the period in which the species of the genus Australopithecus are gradually being replaced by species of the genus Homo, of which we, Homo sapiens are part," he said.
Dr Robyn Pickering is from the School of Earth Sciences at the University of Melbourne, Australia, and was part of the team which aged the fossils.
She said: "It has never been clear where our own genus Homo came from - this new discovery Australopithecus sediba could answer these questions. Knowing how old these early human (hominin) fossils are is critical to our knowledge of where this newly found species fits into our family tree.
"We have been able to date the sediba fossils to between 1.95 and 1.78 million years ago. This is the first time in South Africa, we have been able to achieve such good age control. Now we are able to fill in the gap of what happened two million years ago in the beginnings of our species."