Lucy, the 3.2 million year-old hominin whose bones were one of the most important fossils ever discovered, died from injuries suffered in a fall from a height of some 40 feet.

The incredible piece of forensic investigation that came to this conclusion also found that Lucy probably fell to her death from a tree, an impact that fractured many of her bones. Her death plunging from a great height also confirmed an assumption that Lucy's species -- Australopithecus afarensis -- spent at least some of its life in the trees.

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CT scans of her bones revealed injuries similar to those suffered by modern humans in similar falls. Her death from what scientists fastidiously described as a "vertical deceleration event" crushed a shoulder joint and fractured her ankle, leg bones, pelvis, ribs, vertebrae, arm, jaw and skull.

"We weren't there. We didn't see it. But the subset of fractures that we've identified are fully consistent with what's reported in a voluminous orthopedic surgical literature about fall victims who have come down from height," said Prof. John Kappelman from the University of Texas at Austin, lead author of the report published in the journal, Nature.

"It's tested every day in emergency rooms all around the planet."

Despite the many fractures in Lucy's mineralized bones, it was the shattered top of her humerus bone (the upper arm) that convinced investigators she fell to her death from a tree. Lucy landed on her feet and spread her arm outward to cushion the fall.

"If our hypothesis stands up ... it tells us that Lucy was conscious when she reached out her arms to break her fall," said Prof. Kappelman.

Scientists estimate Lucy was only 1.1 meters tall and is thought to have been a young adult when she died.

Lucy is the common name of AL 288-1. She consists of several hundred pieces of bone fossils representing 40 percent of the skeleton of a female of the hominin species found in Ethiopia.

Lucy was discovered by paleoanthropologist Donald Johanson in 1974 near the village Hadar in the Awash Valley of the Afar Triangle in Ethiopia.

Johanson noted that Lucy has become "an icon of paleoanthropology" and a benchmark against which later discoveries have been compared as scientists seek to understand where various fossils fit into the evolutionary process.

He said the evidence points to Lucy being an adult female about 60 to 65 pounds in weight, with short legs and long arms. She had a softball-size brain, comparable to modern apes, but stood and walked upright as humans do.

The skeleton presents a small skull akin to that of non-hominin apes. She also showed evidence of a walking-gait that was bipedal and upright, akin to that of humans. This combination supports the view of human evolution that bipedalism preceded increase in brain size.

TagsLucy, hominin, ethiopia, Australopithecus afarensis, Prof. John Kappelman, Donald Johanson, paleoanthropology