Meet Sediba, the latest addition to the human family tree.
The well-preserved skull - that of a young boy - belongs to a new species of human ancestor who lived nearly two million years ago.
Scientists believe it may have been a 'missing link' between ape-men and the first ancient humans.
It was among 130 fossils belonging to a boy aged around nine and an adult female, probably in her late 20s or early 30s, who lived between 1.95million and 1.78million years ago.
This female skull forms part of the skeleton Australopithecus sediba. Sediba is thought to have roamed Earth two million years ago
Matthew Berger, nine, shows a rock from the area where he made the remarkable discovery
The remains were discovered by a boy of nine who had joined his father on a fossil-hunting expedition at the Malapa Cave in the Sterkfontein region of South Africa.
Researchers have named the new species Australopithecus sediba- meaning-southern ape, spring'.
They are the most complete bones of any early human ancestor - or 'hominid' - ever found.
Professor Lee Berger of South Africa's University of Witwatersrand who made the find in 2008 with his son Matthew, said: 'These fossils give us an extraordinarily detailed look into a new chapter of human evolution and provide a window into a critical period when hominids made the committed change from dependency on life in the trees to life on the ground.'
Prof Berger assumed Matthew had found a fossilised ancient antelope. But when he took a closer look, he saw that it was a collar bone. As it turned it over in his hands, he saw a hominid lower jaw jutting out.
'I couldn't believe it,' he said.
The bones turned out to belong to the boy. The remains of the female were unearthed the following month and over the next two year, 130 fragments of bone were found.
The oldest known hominid is Ardi - a female member of the Ardipithecus ramidus species that lived 4.4million years ago.
However, the best known is Lucy - a member of the ape-like Australopithecus who lived in Africa 3.2million years ago. Sediba bridges the gap between the Lucy-like Australopithecus and the first Homo species.
Dr Paul Dirks, from James Cook University in Australia, stands close to where the remains were found shortly after it was first discovered and before excavation started
A student abseils down a shaft close to the Sediba site
Prof Lee Berger with the skeleton of the male child, believed to be nine years old - the same age as his son who made the remarkable discovery
Sediba was an upright walker, around 4ft 2in tall, who shared many physical traits with the earliest known Homo species, Homo erectus.
It had long arms, like an ape, short powerful hands, a human-like pelvis and long legs capable of striding and possibly running. Their brains were a third the size of modern humans.
The latest discovery has provoked a debate among scientists over their importance.
The fossils were found in what was once a cave that was 165ft underground 1.9million years ago. The couple appear to have fallen, along with other animals, into a deep cave.
They may have survived the fall for a few days or weeks, living off the meat from other animals trapped with them.
After they died, their bodies were washed into an underground lake or pool where they were covered with sediment and preserved.
The scientists believe they died close to each other in time - possibly hours, days or weeks apart.
Two more skeletons from the same species have been found since the discovery - but their details are being kept secret for now.
The researchers also found fossils from at least 25 other species of animals - including sabre-toothed cats, a wild cat, a brown hyena, a wild dog, antelopes, mice, rabbits and a horse.
Prof Paul Dirks, from James Cook University in Australia, who took part in the dig, said; 'One possible explanation for their entry into the cave could have been that they needed water
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This shows a well-known archaeological site close to where the find was made. Two more skeletons from the same species have been found since the discovery - but their details are being kept secret for now
'Animals may have smelled water, ventured in too deep, fallen down hidden shafts in the pitch dark or got lost and died.'
The discovery has excited fossil experts around the world - and provoked a debate over their importance.
Dr Darren Curnoe a specialist in human evolution from the School of Biological, Earth and Environmental Sciences University of New South Wales Sydney said: 'The discovery of one, let alone two, partial skeletons of the fossil relatives of humans is a rare and truly amazing thing. Added to this, is the remarkably young geological age of these new finds.'
But he claimed the discovery had been surrounded by 'hype and over-interpretation'.
'To claim that these new fossils represent an ancestor of living humans is misleading and founded in error,' he said.
'Australopithecus sediba is the wrong species, in the wrong place, and at the wrong time. It is way too primitive to be the ancestor of the human genus Homo, one of our direct ancestors. For a start, fossil Homo is known from East Africa to be almost half a million years older.
'The skull, tooth, and limb bone anatomy of the older Homo also looks very different from those of sediba. Finally, a number of key skulls compared to the new sediba remains have been incorrectly described leading to false conclusions about its place in human evolution.'
Prof Maciej Henneberg is the Wood Jones Professor of Anthropological and Comparative Anatomy at the University of Adelaide, added: 'I am not sure, whether a designation of a new separate species is necessary.
'In the human lineage there is a natural range of variation of characteristics of individuals and the new finds fit into this range.'
