In this episode, Ashley Judd tells the story of the discovery of a fascinating fossil of a female who lived 4.4-million-years ago. This unexpected find opened up a new window into the very early evolution of the human species.
In this episode, Ashley Judd tells the story of the discovery of a fascinating fossil of a female that lived 4.4-million-years ago. This unexpected find opened up a new window into the very early evolution of the human species.
Further reading
About The Leakey Foundation
The Leakey Foundation is a nonprofit organization dedicated to funding human origins research and sharing discoveries. The Foundation was established in 1968 to fund work at the forefront of fossil and primate studies and provide opportunities for a global community of scientists. Learn more at leakeyfoundation.org.
Discovering Us: 50 Great Discoveries in Human Origins
In 50 lively and up-to-the-minute essays illustrated with full-color photographs, Discovering Us: 50 Great Discoveries in Human Origins presents stories of the most exciting and groundbreaking surprises revealed by human origins research.
Prepared in consultation with leading experts and written by Evan Hadingham, senior science editor for NOVA, Discovering Us features stunning photographs, some taken at the actual moment that groundbreaking discoveries were made. The book presents a highly accessible account of the latest scientific insights into the ultimate question of humanity’s origins. Discovering Us was published by Signature Books.
Find Discovering Us at your local library, bookstore, or amazon.com.
Show Credits:
Discovering Us was made possible by generous support from Camilla and George Smith, the Ann and Gordon Getty Foundation, and the Joan and Arnold Travis Education Fund.
Meredith Johnson:
This is Discovering Us from The Leakey Foundation and Signature Books … an audio companion to the book Discovering Us: 50 Great Discoveries in Human Origins. Written by Evan Hadingham and read for you by Ashley Judd.
I’m your host, Meredith Johnson.
In this installment of Discovering Us you’ll learn about the fascinating fossil of a female that lived 4.4-million-years ago whose discovery opened up a new window into the very early evolution of the human species.
Here’s Ashley Judd…
Ashley Judd:
Unexpected Ardi : a fossil in fragments
On a barren hillslope in the badlands of Ethiopia’s Middle Awash region, a pile of rocks commemorates the passing of an ancestor.
Imitating a local Afar chief’s grave, the cairn marks where one of the oldest creatures to lay claim to human ancestry perished 4.4 million years ago—80,000 generations before the time of Lucy.
Reconstructing the first specimen of Ardipithecus ramidus , nicknamed “Ardi,” took 17 years from the finding of the first fragment until its final publication.
It was perhaps the most challenging reconstruction of any single specimen in the human fossil record, and its painstaking analysis confounded many expectations.
In blistering heat near the village of Aramis, a team spent three seasons with their noses pressed a few inches from the ground. Team leader, paleoanthropologist Tim White said, “Literally, we crawled every square inch of this locality. You crawl on your hands and knees, collecting every piece of bone, every piece of wood, every seed, every snail, every scrap. It was 100 percent collection.”
White calls the dozens of crushed fossil fragments they recovered, calling them, “road kill... so fragile, you couldn’t even breathe on the thing.”
Ardi’s entire skull was so squashed, it was a little over an inch thick. To extract the fragments, the team had to remove the surrounding blocks of sediment, which they then teased apart in the lab under the microscope with dental tools.
Meanwhile, in a lab in Tokyo, White’s colleague Gen Suwa manipulated 3D CT scans of the skull to create a virtual reconstruction; it took him nine years before he was satisfied with the result.
In the end, rarely preserved parts of the skeleton were pieced together, including the delicate hand and foot bones and much of a pelvis.
Why did Ardi’s reconstruction merit such Herculean efforts?
The period between 4—7 million years ago is almost a blank in the hominin fossil record. Yet it marks the crucial first chapter in the human story, when our lineage split off from those leading to living African apes and we made the transition to upright walking.
For much of the last century, scientists assumed that the common ancestor we shared with chimpanzees before the split would have had features that foreshadowed chimp adaptations, such as a pelvis and limbs suited for knuckle walking.
Then, as our ancestors began to walk upright, they would have lost those features while the forerunners of today’s chimps and gorillas retained them.
But Ardi turned out to be a highly distinctive creature. At about four feet tall and 110 pounds, she was bigger than Lucy but had a slightly smaller brain than average for Lucy’s species.
She did have some chimp-like traits: long and powerful forearms, long curving fingers, and an opposable big toe, good for grasping branches. Clearly, she was a strong climber at home in the trees.
Yet her hands lacked the special adaptations that knuckle-walk- ing chimps have to support the weight of their bodies. Instead, Ardi was a competent upright walker.
While chimps lurch clumsily from side-to-side when they walk upright, Ardi’s pelvis was adapted so she could walk more efficiently and smoothly. Its wing-like upper part was shaped like our own, providing attachment points for gluteal muscles that helped stabilize her stride.
Besides her grasping big toe, her other toes pointed straight ahead and could flex upward at the end of a stride just as our toes do.
Recently, fragments of a new Ardipithecus skeleton were discovered at Gona, Ethiopia, during work supported by The Leakey Foundation. According to paleoanthropologist Scott Simpson of the Gona team, the find reveals slight differences in the ankle bone and big toe that suggest an even more human-like gait than the original remains did.
Not that she walked entirely as we do today. According to White, “her short legs, long arms, and splayed big toes add up to a creature that is neither human nor chimpanzee, and only accessible through the fossil record.”
White believes that the long-held “proto-chimp” image of our last common ancestor could be wrong ; instead, chimpanzees and gorillas may have evolved into their distinctive forms more recently, well after they split away from us.
But uncertainty over how Ardi relates to the human story is likely to continue. Paleoanthropologist Jeremy DeSilva points out that “fossils do not come with labels, and the closer in time a fossil gets to the common ancestor of humans and the African apes, the more difficult it becomes to differentiate between extinct members of the human, chimpanzee, and gorilla lineages.”
Only new fossil discoveries of distant ancestors will help resolve the uncertainty; meanwhile, Ardipithecus opens up a window on an early stage in our evolution that nobody predicted.
[MUSIC rises and then ducks under closing credits]
Meredith Johnson:
Discovering Us: 50 Great Discoveries in Human Origins was written for The Leakey Foundation by Evan Hadingham. It was published by Signature Books. The stories are read for you by Ashley Judd.
All the episodes of this audio-companion are available to listen to right now! Make sure to subscribe and share this series with a friend.
You can buy a copy of Discovering Us at your local bookstore or wherever you buy books. There’s a link in the shownotes.
The Leakey Foundation is a nonprofit organization dedicated to funding human origins research and sharing discoveries. The science you heard about today was made possible by Leakey Foundation supporters. Visit our website to learn how you can get involved. Go to leakeyfoundation.org. That’s l-e-a-k-e-y foundation dot org.
This project was made possible by generous support from Camilla and George Smith, the Joan and Arnold Travis Education Fund, and the Ann and Gordon Getty Foundation