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Prehistoric World

'Lucy's Baby' Discovery

Edited from BBC News, 20 September 2006

The 3.3-million-year-old fossilised remains of a human-like child have been unearthed in Ethiopia's Dikika region.

At this time Australopithecus afarensis continued to roam a mixed habitat of savannah and woodland beside lakes and floodplains, foraging for fruit, seeds and nuts and maybe even some meat. They probably climbed into trees to avoid sabre-toothed cats such as dinofelis and to sleep in safety at night.

This particular female child's afarensis bones are from the same species as an adult skeleton found in 1974 which was nicknamed 'Lucy'. Scientists are thrilled with the find, as reported in the journal Nature.

They believe the near-complete remains offer a remarkable opportunity to study growth and development in an important extinct human ancestor. Juvenile Australopithecus afarensis remains are vanishingly rare. The skeleton was first identified in 2000, locked inside a block of sandstone. It has taken five years of painstaking work to free the bones.

'The Dikika fossil is now revealing many secrets about Australopithecus afarensis and other early hominins, because the fossil evidence was not there,' said dig leader Zeresenay Alemseged, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Delicate bones

The find consists of the whole skull, the entire torso and important parts of the upper and lower limbs. CT scans reveal unerupted teeth still in the jaw.

This is a detail which makes scientists think the individual may have been about three years old when she died.

Remarkably, some quite delicate bones not normally preserved in the fossilisation process are also present, such as the hyoid, or tongue, bone. The hyoid bone reflects how the voice box is built and perhaps what sounds a species can produce.

The researchers decided that, judging by how well it was preserved, the skeleton may have come from a body which was quickly buried by sediment in a flood.

'In my opinion, afarensis is a very good transitional species for what was before four million years ago and what came after three million years,' Doctor Alemseged said. '[The species had] a mixture of ape-like and human-like features.

[They seem to have lived in social groups of between twenty and thirty strong. These groups were probably like those of chimpanzees, with dominance hierarchies in which each individual knows their place. ] This puts afarensis in a special position [in which it could] to play a pivotal role in the story of what we are and where we come from.'

Climbing ability

This early ancestor possessed primitive teeth and a small brain but it stood upright and walked on two feet.

  This puts afarensis in a special position to play a pivotal role in the story of what we are and where we come from

Zeresenay Alemseged
Max Planck Institute

There is considerable argument about whether the Dikika girl could also climb trees like an ape.

This climbing ability would require anatomical equipment like long arms, and the 'Lucy' species had arms which dangled down to just above the knees. It also had gorilla-like shoulder blades which suggest it could have been skilled at swinging through trees.

But the question is whether such features indicate climbing ability or are just 'evolutionary baggage'.

The Dikika girl had an estimated brain size of 330 cubic centimetres when she died, which is not very different from that of a similarly aged chimpanzee. However, when compared to the adult afarensis values, it forms between 63-88% of the adult brain size.

This is lower than that of an adult chimp, where by the age of three, over 90% of the brain is formed. This relatively slow brain growth in the Dikika girl appears to be slightly closer to that of humans.

Slow, gradual development in an extended childhood is regarded as a very human trait - probably to enable our higher functions to develop.

Professor Fred Spoor of University College London said the find would give scientists a 'detailed insight into how our distant relatives grew up and behaved... at a time in human evolution at which they looked a good deal more like bipedal chimpanzees than like us'.

Dr Jonathan Wynn of the University of St Andrews in the UK and colleagues at the University of South Florida dated the sediments surrounding the remains and came up with an age of 3.3 million years.

The 'Lucy' skeleton, discovered in Hadar, Ethiopia, in 1974 belongs to the same species as the Dikika girl. For more than twenty years it was the oldest human ancestor known to science.



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