Profile: Ardi: Our 4.4 million-year-old granny

PICTURE the scene. It's the African savanna of Ethiopia, 4.4 million years ago. Tuesday, to be exact, somewhere around tea-time. There is a rustle among the long grass and in the distance an elephant trumpets its annoyance, scattering parrots from the trees and sending shrews and mice scuttling deeper into the undergrowth.

A small, hairy head turns, cocks her ear and waits till any danger has passed. Ardi, as she will come to be known, is four feet tall, weighs 120 lbs and has a thin body covered in matted hair. She has very short legs and exceedingly long arms, but short palms and fingers which are flexible enough to allow them to support her entire body weight on her palms.

While her feet lack an arch-like structure, she can still walk upright but possesses a grasping big toe for when she clambers on all fours among the trees. Her upper canine teeth are not long and sharp like a chimps, but stumpy and handy for grinding through fruits, nuts, leaves and, when she's swift enough to catch them, the occasional small mammal. Although it is rude to comment on a female's love life, there is talk of her trading food for sex then settling into a monogamous relationship with the fruit-winner. She's left behind the days when her forebears were the forced prize of the vicious victor. She's the height of modernity.

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So who is this Ms Ardi? Well, that depends. If, for instance, you are a fundamentalist Christian who believes in the literal truth of the Bible, or a devout Muslim bound by the pages of the Koran, she's nothing more than a myth, a fictitious rumour conjured up by the godless from a few dusty old animal bones. If, however, you are a student of evolution, a disciple of Charles Darwin, and believe that science and archaeology can, like a flaming torch in the dark, illuminate the past she's none other than your granny.

Your great, great, great… (insert roughly 176,000 greats) …granny.

For when she lay down to die, in what is now an arid floodplain along the middle stretch of the Awash River in Ethiopia, she had no idea – c'mon she's a brain the size of a chimp, how could she? – that millennia of millenniums hence, 1994 to be precise, a Japanese paleoanthropologist would uncover a single upper molar and so begin a process of discovery that would be hailed, when the full findings were published last week, as the greatest find in decades.

So why all the excitement about Mrs Ardi? Well, she is another link in the great chain of bone and DNA that unites us, Homo sapiens, with a mammal who existed sometime before six million years ago and who is a common ancestor of both us and the chimpanzee. While she is not the 'missing link', she is the oldest and perhaps most important link so far, in that she lived one million years before the earliest find. In the gallery of human origins stand key exhibits that tell the story of hominid evolution: at 1.6 million years old there is Turkana Boy from Kenya, an almost complete specimen of Homo erectus; then at 3.2 million year-olds, there is Lucy, the skeleton of the species Australopithecus afarensis; and now to this distinguished glass case we can add, at 4.4 million years, Ardi, which is short for Ardipithecus ramidus.

After 17 years of research by an international team of 47 scientists, the 'biography' of Ardi, as published across 11 papers in this week's edition of Science magazine, is well timed, coming as it does, in the year of the 150th anniversary of the publication of Charles Darwin's earth-shattering text, On the Origin of Species. "This is not that common ancestor, but it's the closest we have ever been able to come" said Dr Tim White, director of the Human Evolution Research Centre at the University of California. He noted that Charles Darwin was cautious about the last common ancestor between humans and apes. "Darwin said we have to be really careful. The only way we're really going to know what this last common ancestor looked like is to go and find it. Well, at 4.4 million years ago we found something pretty close to it."

And it required considerable effort. Ardi's skeleton had been trampled and scattered with her skull crushed to just two inches in height, but the scientists were diligent in their reconstruction, piecing together 125 fragments of bone, including much of her skull, hands, feet, arms, legs and pelvis. The results have been surprising. Previously, scientists believed that our common ancestor would have been very chimp-like and that ancient hominids such as Ardi would still have much in common with them. However, she was not suited like a modern-day chimp to swinging or hanging from trees or walking on her knuckles, which suggests that chimps and gorillas developed those characteristics after the split with humans, which challenges the idea that they are merely an 'unevolved' version of us.

Other areas that now require more consideration include the conventional wisdom which said earliest ancestors first stood up on two legs when they moved out of the forest and into the open savannas. Yet this does not explain why Ardi's species was able to walk on two legs while still living partly in the trees. Owen Lovejoy from Kent State University said this week that the answer could be as simple as food and sex. He pointed out that throughout evolution males have fought with other males for the right to mate with fertile females. Therefore you would expect dominant males with big fierce canines to pass their genes down the generations. But what if a lesser male, with small stubby teeth realised he could entice a fertile female into mating by bringing her abundant food? Males would be far more successful food-providers if they walked on two legs and so had their hands free to carry home items like fruit and roots. Lovejoy said this could explain why males from Ardi's species had small canines and stood upright and added that it could also suggest that monogamous relationships may be far older than was first thought.

Yet all this is heresy for those who believe the world is barely a few thousand years old and that Adam and Eve strolled through an Eden populated by dinosaurs. In the film, Creation, recently released, Darwin's struggle to reconcile his wife's fervent Christianity with his own agnosticism finds a curious echo in the chatter on the comment boards following the announcement of Ardi. Anne from Suffolk wrote: "this article is a joke and so too is the theory, i repeat, THEORY of evolution." She was then supported by a contributor from Philadelphia, yankee doodle dandy, who wrote: "Do not believe this at all. We were created in the image of God. What scares me is all of you who believe it!" While Dom, from Durham, may have retorted: "hahaha, get an education", he was followed by someone more succinct, to whom Ardi proved that God did not create us in his image: "We created God in ours."


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• Ardi is short for Ardipithecus ramidus or "root of the ground ape".

• Volcanic layers around the fossil were used to date it from 4.4 million years ago.

• Since the discovery, scientists have unearthed another 35 members of the Ardipithecus family.

• Ardi was found alongside crumbling fossils of 29 species of birds and 20 species of small mammals including owls, parrots, shrews, bats and mice.

• Alan Walker, of Pennsylvania State University, commented: "These things were very odd creatures. You know what someone once said: 'If you wanted to find something that moved like these things you'd have to go to the bar in Star Wars (left].'"

• The search continues for the "last common ancestor" from which both modern humans and modern chimpanzees can trace their ancestry. Many experts think the common ancestor lived at least seven million years ago.