What are scientists so excited about?
Scientists in Ethiopia have discovered the fossilised remains of a child 3.3 million years old that represents an intermediate stage between chimpanzees and humans. Dubbed "Selam", which means "peace" in the local language, the little girl has a lower body much like a human, well adapted to walking upright, while the upper body is closer to that of a chimpanzee - which may indicate that she was able to climb trees like a chimp. She also has a face, and her chewing teeth are much closer to those of a human than to the large pointed canines of a chimpanzee. She is expected to be "a veritable mine of information about a crucial stage in human evolutionary history", as Bernard Wood, of the Department of Anthropology in George Washington University, puts it in the current issue of Nature, where the discovery was announced. The team who made the discovery are cock-a-hoop because it is unusual for the fragile bones and head of a child to survive from remote antiquity. As Professor Wood writes: "One must travel forward in time more than three million years... to find a comparably complete hominim infant skeleton."
What will the find tell us that we didn't know?
Because the sandstone that encased her retained an impression of her brain, she will tell scientists a lot about how the brain developed in her species. Selam's feet are still encased in sandstone; once they have been liberated, we will learn whether she has grasping toes like a chimp or toes closer to those of a human. This will help to resolve a controversy that is already raging over her remains: do her rounded, gorilla-like shoulder blades and curved, chimpanzee-like fingers indicate that she and her relatives still roamed through the trees as well as walking upright on the ground? Or were these features just "evolutionary baggage" that were no longer in use?
And why is this significant?
Selam is expected to shed more light on our evolutionary voyage. The skeleton has features that its finders claim are remarkable examples of the intermediate stage of evolution between apes and humans. The existence of this intermediate creature "confirms the idea," says Rick Potts of the Smithsonian Institution, "that human evolution was not some straight line going from ape to human."
Zeresenay Alemseged, paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology at Leipzig, whose international team made the discovery told Nature: "These hominid fossils clearly show evolution in the making".
How was the child's body preserved?
It looks as if she tumbled into a stream and drowned. Perhaps a flash flood buried her intact remains in sand. The sand subsequently hardened to encase the bones. In 2000 an expedition led by Professor Alemseged, was travelling in the Dikika region of north-eastern Ethiopia, an area justly known as "the cradle of humanity", when a member of the team spotted the face of a skull protruding from a steep hillside. After the discovery, Zeresany Alemseged and his team spent five years chipping away the cement-like sandstone matrix in which the delicate bones were encased.
The effort was rewarded with the retrieval of a remarkably complete skeleton: the pelvis, the lowest part of the back and parts of the limbs are yet to be found, but the face, brain case, lower jaw, collar bones, many ribs and knee caps are present and correct.
Is she related to Lucy?
Yes. Like Lucy - the most famous fossil of the early human ancestor - she is a member of the Australopithecus afarensis species. Lucy, who was discovered at Hadar in Ethiopia in 1974 and reshaped theories of human evolution, lived tens of thousands of years more recently than Selam. Despite that some experts have not been able to resist calling the new discovery "Lucy's baby". But Selam may come to outshine Lucy in terms of what she tells us, simply because she is so much more complete: only about 40 per cent of Lucy was recovered.
Is Selam linked to "the Hobbit"?
Not in any meaningful sense. In March scientists on the island of Flores in the Malay Archipelago announced that they had found the skeleton of an entirely new species of human, Homo floresiensis, that walked the earth only 18,000 years ago, long after the development of homo sapiens. Rapidly dubbed "the hobbit" by journalists, "Flores", a female, stood only three feet high and was claimed to be the first confirmed case of "island dwarfing" in the evolution of man.
This is the tendency for mammals trapped on small islands to shrink over the generations in order to survive with limited resources. This discovery threatened to render obsolete the accepted image of human evolution as "the ascent of man" and replace it with a new vision of diversity, in which homo sapiens shared his environment with other varieties of human creature. However, that tantalising vision has been cast into doubt: last month, as reported in The Independent, a learned journal published claims that the "hobbit" is no more than a very unfortunate member of our own species, whose tiny body and brain were the product of a severe congenital disorder.
Could Selam also disappoint?
Her future seems far more assured. There seems little doubt the fossil is 3.3 million years because of sediments containing evidence of the same layers of ash that have allowed researchers to date other East African fossil sites. Her chronological age, thought to be three, is yet to be confirmed. And while other examples of her species have been found, Selam is, we are told, the first to come with a whole shoulder blade. It is this bone's traits which indicate a cross between an ape capable of swinging from the trees and a modern human. Selam's grinning, computer-generated face is shortly to star on the cover of National Geographic.
Have scientists unravelled a key mystery in the roots of the human race?
* The skeleton is that of the earliest child ancestor of humans ever found and is almost complete
* The bones indicate that this is a creature partway between ape and modern human thus crucial in understanding man's origins
* An intact skull and imprint of the creature's brain provide a minefield of new information on evolution
* This is not the first member of the Australopithecus afarensis species to be discovered
* Research teams have made sensational announcements in the past only to be proved wrong
* We don't know what the foot bones will reveal and this could be crucial in determining Selam's place in evolution