Lucy, Homo sapiens' most famous ancestor from more than 3 million years ago, died when she fell out of a tree. Or did she?

Her skeletal remains indicate she suffered breaks to her right arm, left shoulder, right ankle and left knee, which anthropologist John Kappelman, a professor at the University of Texas at Austin, said were consistent with the blunt force trauma of falling from a height of about 40 feet (12 meters), and hitting the ground at 35 mph (55 kph).

Her injuries suggest "she stretched out her arms at the moment of impact in an attempt to break her fall," said Kappelman, who co-authored the study. "That tells us that Lucy was conscious at the point of impact, and that instant in time right before her death."

Lucy, 3-foot-6-inch, belonged to an early human species known as Australopithecus afarensis. The earliest humans climbed trees and walked on the ground.

Lucy walked upright and occasionally used her long, dangling arms to climb trees. She was a young adult when she died.

Over a 10-day period the researchers used high-resolution 3D scans, or computerized tomography (CT) scans, on the Lucy fossil - one of the most complete hominin fossil skeletons ever discovered.

Her fractures were generally consistent with a traumatic impact such as a fall from a "considerable" height, the researchers concluded.

"It's very likely she suffered severe internal organ damage, on likely every organ and death followed very swiftly," Kappelman said. "I don't think she suffered.

Believe it, or not

But not everyone buys his fall from the trees argument, including the man who discovered Lucy's bones in Ethiopia in 1974. Donald Johanson, of Arizona State University, has spent years trying to solve the mystery of Lucy's death.

"There's no definitive proof of how she died," he said.

Tim White, a paleoanthropologist at the University of California, Berkeley agreed, called the study's conclusion a "misdiagnosis."

The Texas researchers "appear to have focused only on the cracks that they could attribute to an imagined fall, ignoring the additional abundant cracks," White said

Critics said the damage to Lucy's bones might have occurred in any number of ways, including during the millions of years after her death.

But Kappelman is standing by his research conclusions, and said it made Lucy more real.

"For me, understanding her death brought her to life for me for the first time," Kappelman said. "When I better understood the potential cause of her death, I could picture her broken body lying there at the foot of the tree. I could empathize with her."

bik/kms (AP, AFP)