Ardi: Oldest Human Ancestor 4.4 Million Years Old

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She lived at the dawn of a new era, when chimps and people began walking (or climbing) along their own evolutionary trails. This is Ardi – the oldest member of the human family tree we’ve found so far. Short, hairy and with long arms, she roamed the forests of Africa 4.4million years ago.

Her discovery, reported in detail for the first time today, sheds light on a crucial period when we were just leaving the trees.
‘This is one of the most important discoveries for the study of human evolution,’ said Dr David Pilbeam, curator of palaeoanthropology at Harvard’s Peabody Museum of Archaeology and Ethnology.
‘It is relatively complete in that it preserves head, hands, feet, and some critical parts in between.’

Ardi – short for Ardipithecus ramidus or ‘root of the ground ape’ – stood 4ft tall and weighed 110lb. She lived a million years before the famous Lucy, the previous earliest skeleton of a hominid who was dug up in 1974. Experts believe Ardi is very, very close to the ‘missing link’ common ancestor of humans and chimps, thought to have lived five to seven million years ago.

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‘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, Berkeley, who reports the discovery today in Science. The first fossilised and crushed bones of Ardi were found in 1992 in Ethiopia’s Afar Rift.

But it has taken an international team of 47 scientists 17 years to piece together, analyse and describe the remains.

Ardi’s skeleton had been trampled and scattered, while the skull was crushed to just two inches in height.
Researchers have pieced together 125 fragments of bone – including much of her skull, hands, feet, arms, legs and pelvis – which were dated using the volcanic layers of soil above and below the find.

The results were 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.

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But she was not suited like a modern- day chimp to swinging or hanging from trees or walking on her knuckles. This suggests that chimps and gorillas developed those characteristics after the split with humans – challenging the idea that they are merely an ‘unevolved’ version of us.

Ardi’s feet were rigid enough to allow her to walk upright some of the time, but she still had a grasping big toe for use in climbing trees.

And she had long arms but short palms and fingers which were flexible, allowing her to support her body weight on her palms. Her upper canine teeth are more like the stubby teeth of modern people than the long, sharp ones of chimps. An analysis of her tooth enamel suggests she ate fruit, nuts and leaves.

Scientists believe she was a female because her skull is relatively small and lightly built. Her teeth were also smaller than other members of the same family that were found later.

Alan Walker, of Pennsylvania Sate University, told Science: ‘These things were very odd creatures. You know what Tim (White) once said: ‘If you wanted to find something that moved like these things you’d have to go to the bar in Star Wars’.’

Since the discovery, scientists have unearthed another 35 members of the Ardipithecus family. Ardi was found in alongside crumbling fossils of 29 species of birds and 20 species of small mammals – including owls, parrots, shrews, bats and mice.

(source)

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