'Lucy's baby' found in Ethiopia

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

The female bones are from the species Australopithecus afarensis , which is popularly known from the adult skeleton nicknamed "Lucy".

They believe the near-complete remains offer a remarkable opportunity to study growth and development in an important extinct human ancestor.

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.

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, a detail that 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.

Judging by how well it was preserved, the skeleton may have come from a body that was quickly buried by sediment in a flood, the researchers said.

"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," Dr Alemseged told BBC science correspondent Pallab Ghosh.

"[The species had] a mixture of ape-like and human-like features. This puts afarensis in a special position to play a pivotal role in the story of what we are and where we come from."

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

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 that 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 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 of human evolution when they looked a good deal more like bipedal chimpanzees than like us."

The "Lucy" skeleton, discovered in Hadar, Ethiopia, in 1974 belongs to the same species as the Dikika girl. For more than 20 years it was the oldest human ancestor known to science.

The amazing fossil of 'Lucy's little sister'

20 September 2006
From New Scientist Print Edition.
Jeff Hecht

The stunningly complete skeleton of a three-year-old girl who lived 3.3 million years ago has been uncovered in Ethiopia. The child belongs to the species Australopithecus afarensis like the famous "Lucy", who was discovered in 1974. The young age of the so-called Dikika child promises new insights into the growth of early humans.

The new find is the most complete and important skeleton of an immature Pliocene hominin ever found, says Tim White of the University of California, Berkeley, who worked on the Lucy discovery. "The gist of the current paper is, 'Eureka, we have it'," he says.

A team led by Zeresenay Alemseged of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, spotted the first bones south of the Awash river on 10 December 2000. The team spent four field seasons scouring the area for every scrap of the skeleton.

Lucy was also found in the Awash region, which is famed for its early human fossils. Many anthropologists think A. afarensis was ancestral to the genus Homo, though its exact position in the human family tree remains a matter for debate.

Alemseged's team believes that a flood rolled the child's body into a ball and buried it in sand soon after her death, before the bones could be weathered or pulled apart by scavengers.

Analysis of the skeleton has barely begun because the upper parts, including the skull, shoulder blades, collarbones, ribs and backbone, are still largely encased in a block of hard sandstone. However, a CT scan of the skull revealed tooth development matching that of a three-year-old, the team reports in Nature (vol 443, p 296).

"At least 50 per cent of the skeleton is there, but more importantly we have the face and brain endocast, and the whole skull, telling us clearly how the [child] looked," says Alemseged. He estimates the brain size was 330 cubic centimetres, between 63 and 88 per cent of the size of an adult of the species. This hints at brain growth slower than in chimpanzees, whose brains have reached 90 per cent of adult volume by age three. A. afarensis may therefore have begun evolving the slower brain development characteristic of modern humans.

The exposed leg bones show the child walked bipedally like Lucy. In contrast, the shoulder blade "in some ways resembles young gorillas", says collaborator Bill Kimbel of Arizona State University. That supports the inference from Lucy's long arms that she was a better climber than modern humans. During the girl's lifetime the environment was a mosaic of forest and savannah, so the species may have gathered food and slept in trees, but walked from place to place.

Another key discovery is a hyoid bone, which is found in the throat and in humans is involved in speech. Until now, only one fossil hyoid has ever been found, and it was from a Neanderthal. The Dikika hyoid resembles an ape's, suggesting speech had not begun to evolve in A. afarensis.

Alemseged believes much information can be gained once the skeleton is freed from its stone casing. "A clear picture will emerge of how baby human ancestors were built, and how they grew up," he says.

If the species is extinct then how is it an ancestor of modern humans? If it has living descendants then it is NOT extinct. You could say it is "mutated" or "evolved" but not "extinct." The individual, however, is surely extinct.

I think you are offering a new definition of "species." For most fossilized bones, species is classified on general shape (morphology). For currently living species, classification is (usually) based on ability to inter-breed.

These critters, Lucy and this new girl, are morphologicallly distinct from humans and therefore a distinct species. Since that morphology doesn't exist anymore in any known living creatures, it is considered an extinct species.

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.