Africa skeleton: 3 years old, about 3.3 million years old

Scientists reveal most ancient complete set of child bones on record

September 21, 2006|By Robert Lee Hotz | Robert Lee Hotz,Los Angeles Times

No one knows how her body came to be in the stream or how long her distraught parents might have searched the shallows for the missing 3-year-old.

The child's fossilized skeleton - a tiny skull, a jaw with baby teeth still intact, a clutch of finger bones, the curled commas of ribs - are the remains of a domestic calamity 3.3 million years ago when the human family was in its infancy, so long ago that the river in which she might have drowned has turned to stone.

Discovered in Ethiopia, her primitive skeleton is the most ancient complete set of infant remains on record, at least 3 million years older than any other comparable fossil of childhood, scientists announced yesterday in the journal Nature.

The tiny female was the child of an ancestral pre-human species called Australopithecus afarensis, the same species as the iconic fossil specimen Lucy - long celebrated in the popular imagination as a symbol of human evolution. Their kind thrived in East Africa between 3 million and 4 million years ago. Modern humankind, by comparison, arose just 200,000 years ago.

The subject of intense scientific scrutiny, the child's bones are yielding rare insights into the origins of upright walking, brain development, the beginnings of speech and the unique pace of childhood development that sets humankind apart from all other primates, the researchers said.

Displaying the shoulders of a young gorilla and legs jointed more like a human girl, her bones merge the anatomy of humanity's most ancient ancestors with more contemporary human characteristics, several experts said. She might have deftly swung from branches but also easily walked erect, even at the age of 3, the fossils suggest.

"For us, the excitement is that this is a young child in the middle of a period when lots and lots of growth is happening, when the brain is developing, when the teeth are erupting, when the limb bones are growing," said paleo-anatomist Fred Spoor at the University College London, who studied the find.

Indeed, her bones contain "the biography of a species," said paleo-anthropologist Zeresenay Alemseged, at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who led the international research team that made the find.

So far, they have found her entire skull, containing a natural sandstone impression of her growing brain, as well as most of her torso and limbs. One knee joint was covered by a kneecap no bigger than a dried pea, the researchers said.

"It is a very special discovery," said anthropologist Bernard Wood, an expert on human origins at George Washington University who was not involved in the research. "The degree of completeness is without parallel in a fossil this early."

Her brain was small, measuring not much more than a chimpanzee of the same age. Her finger bones were curved and almost as long as a chimp's, suggesting to researchers that she might have used them to cling to her mother or, more tellingly, to branches.

In the same way, the shape of the infant's inner ear, crucial to balance and equilibrium when moving, appeared more ape-like than human, the researchers reported.

All told, it took Alemseged five years to partially clean and analyze the tiny skeleton, picking away the sandstone encrusting the bones a grain at a time with dental tools. Several more years of work will be necessary before all the bones can be entirely freed from the stone.

Based on the geological evidence, the creature dwelt in an ancient world of lush forests and grassland along a sluggish river delta where braided streams meandered into a lake. The bones were found in sediments that formed at the bottom of a small stream channel.

"The chances of this happening are almost millions to one," Wood said. "It takes your breath away."

Robert Lee Hotz writes for the Los Angeles Times.

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