WASHINGTON – The story of humankind is reaching back another million years as scientists learn more about "Ardi," a hominid who lived 4.4 million years ago in what is now Ethiopia. The 110-pound, 4-foot female roamed forests a million years before the famous Lucy, long studied as the earliest skeleton of a human ancestor.
This older skeleton reverses the common wisdom of human evolution, said anthropologist C. Owen Lovejoy of Kent State University.
Rather than humans evolving from an ancient chimp-like creature, the new find provides evidence that chimps and humans evolved from some long-ago common ancestor — but each evolved and changed separately along the way.
"This is not that common ancestor, but it's the closest we have ever been able to come," said Tim White, director of the Human Evolution Research Center at the University of California, Berkeley.
The lines that evolved into modern humans and living apes probably shared an ancestor 6 million to 7 million years ago, White said in a telephone interview.
But Ardi has many traits that do not appear in modern-day African apes, leading to the conclusion that the apes evolved extensively since we shared that last common ancestor.
A study of Ardi, under way since the first bones were discovered in 1994, indicates the species lived in the woodlands and could climb on all fours along tree branches, but the development of their arms and legs indicates they didn't spend much time in the trees. And they could walk upright, on two legs, when on the ground.
Formally dubbed Ardipithecus ramidus — which means root of the ground ape — the find is detailed in 11 research papers published Thursday by the journal Science.
"This is one of the most important discoveries for the study of human evolution," said David Pilbeam, curator of paleoanthropology at Harvard's Peabody Museum of Archaeology and Ethnology.
"It is relatively complete in that it preserves head, hands, feet and some critical parts in between. It represents a genus plausibly ancestral to Australopithecus — itself ancestral to our genus Homo," said Pilbeam, who was not part of the research teams.
Scientists assembled the skeleton from 125 pieces.
Lucy, also found in Africa, thrived a million years after Ardi and was of the more human-like genus Australopithecus.
"In Ardipithecus we have an unspecialized form that hasn't evolved very far in the direction of Australopithecus. So when you go from head to toe, you're seeing a mosaic creature that is neither chimpanzee, nor is it human. It is Ardipithecus," said White.
White noted that Charles Darwin, whose research in the 19th century paved the way for the science of evolution, was cautious about the last common ancestor between humans and apes.
"Darwin said we have to be really careful. The only way we're really going to know what this last common ancestor looked like is to go and find it. Well, at 4.4 million years ago we found something pretty close to it," White said. "And, just like Darwin appreciated, evolution of the ape lineages and the human lineage has been going on independently since the time those lines split, since that last common ancestor we shared."
Some details about Ardi in the collection of papers:
• Ardi was found in Ethiopia's Afar Rift, where many fossils of ancient plants and animals have been discovered. Findings near the skeleton indicate that at the time it was a wooded environment. Fossils of 29species of birds and 20 species of small mammals were found at the site.
• Geologist Giday WoldeGabriel of Los Alamos National Laboratory was able to use volcanic layers above and below the fossil to date it to 4.4 million years ago.
• Ardi's upper canine teeth are more like the stubby ones of modern humans than the long, sharp, pointed ones of male chimpanzees and most other primates. An analysis of the tooth enamel suggests a diverse diet, including fruit and other woodland-based foods such as nuts and leaves.
• Paleoanthropologist Gen Suwa of the University of Tokyo reported that Ardi's face had a projecting muzzle, giving her an ape-like appearance. But it didn't thrust forward quite as much as the lower faces of modern African apes do. Some features of her skull, such as the ridge above the eye socket, are quite different from those of chimpanzees. The details of the bottom of the skull, where nerves and blood vessels enter the brain, indicate that Ardi's brain was positioned in a way similar to modern humans, possibly suggesting that the hominid brain may have been already poised to expand areas involving aspects of visual and spatial perception.
• Ardi's hand and wrist were a mix of primitive traits and a few new ones, but they don't include the hallmark traits of the modern tree-hanging, knuckle-walking chimps and gorillas. She had relatively short palms and fingers which were flexible, allowing her to support her body weight on her palms while moving along tree branches, but she had to be a careful climber because she lacked the anatomical features that allow modern-day African apes to swing, hang and easily move through the trees.
• The pelvis and hip show the gluteal muscles were positioned so she could walk upright.
• Her feet were rigid enough for walking but still had a grasping big toe for use in climbing.
The research was funded by the National Science Foundation, the Institute of Geophysics and Planetary Physics of the University of California, Los Alamos National Laboratory, the Japan Society for the Promotion of Science and others.
Comments
oui
Posted on: 10/01/2009 22:32
Ooops! Sorry all that html code got in there, how can I edit that out?
lastpointe
Posted on: 10/02/2009 05:45
Fascinating.
I saw this on the news (CBC) last night.
the science guy was sure excited. (I love his radio show Quirks and Quarks)
But I feel bad for porr old fossilied Lucy who now loses her treasured spot as earliest fossil.
jon71
Posted on: 10/02/2009 05:59
Fascinating.
I saw this on the news (CBC) last night.
the science guy was sure excited. (I love his radio show Quirks and Quarks)
But I feel bad for porr old fossilied Lucy who now loses her treasured spot as earliest fossil.
More tragic is that we just lost Lucy Vodden (O'Donnell). She was a childhood school-mate of Julian Lennon. He came home from nursery school with a wild picture. His dad asked him who it was and he said it was Lucy in the sky with diamonds, and that's exactly what he had drawn. His dad obviously used that for a song and the song was playing on the radio when Lucy, the fossil, was discovered. Lucy (real life) had reacquainted with Julian Lennon recently when he found out she was suffering from Lupus. That is what killed her.
Zeusaphone
Posted on: 10/02/2009 07:35
It's not earth-shattering. It's some evidence that bipedal hominids go further back than previously thought. Interesting, and a valuable contribution to the wealth of information on human evolution, but it's not going to shift much in biology.
C. Owen Lovejoy needs to tone his hyperbole down. That kind of excitable sound bite is just what the media love to quote, but obfuscates scientific discussion.
graeme
Posted on: 10/02/2009 07:43
let's see. She's four feet tall and weighs 110 pounds. Chunky kid. And she has a big toe suitable for climbing. Hey! I dated her in high school.
Whether this advances biology has nothing to do with the excitement, Nor do I care much about what it might be that arouses biologists out of their torpor. It is extraordinarily exciting news for us, the ordinary people who pay the salaries of all those biologists who are too sophisticated to get excited.
Zeusaphone
Posted on: 10/02/2009 08:04
oui
Posted on: 10/02/2009 09:39
The individual research papers are being made available for free on the Science magazine web site here:
www.sciencemag.org/ardipithecus/
Absolutely fascinating stuff, tremendous amount of research into a very important creature.
Perhaps "Lucy" is relieved to have the pressure of being #1 off for awhile!
Elanorgold
Posted on: 10/02/2009 12:13
Hey neet! Thanks Oui. She's one hairy gorilla woman!
InannaWhimsey
Posted on: 10/02/2009 12:31
We need more hairy gorilla women!
Oui, thanks for this. There is so much "out there" :3
(for more ancient world fun, check out what they're unearthing in Turkey: http://www.smithsonianmag.com/history-archaeology/gobekli-tepe.html?c=y&...)
Just a Self-writing poem,
Inannawhimsey
Witch
Posted on: 10/02/2009 12:26
A transitional fossil.... interesting
Let's put it on the pile of thousands of other transitional fossils the Creationists claim don't exist.
Dcn. Jae
Posted on: 10/02/2009 17:24
If a different-animal-evidence has been found, I view that as quite wonderful. I believe it to be yet one more thing that God chose to create. I reject the concept that it is years-old-millions, and that it is any ancestor-to-humans-kind. I continue to praise God for what I value as his glorious creation.
seeler
Posted on: 10/02/2009 20:21
I love learning about human evolution. I find it helps us to understand who we are, how were got here, and why we act the way we do. I find it interesting that we continue to find more fosils and proof that moves our origins back further and further. But I don't see anything new in this. Of course humans and chimps and other great apes split from a common tree millions of years ago. And of course modern day apes have evolved and developed to be quite different from that common ancestor - just as modern humans have evolved and developed over time, and continue to do so. And nothing I have read or heard has shaken my faith in God.
Mendalla
Posted on: 10/02/2009 20:25
Fascinating.
Indeed. Read a couple articles about Ardi earlier today and this looks like another important step in finding out where we came from. Wish this had come out before I did my service a couple weeks ago, though. Theme was creation myths and the sermon was on the Big Bang/Evolution . Twould have been a nice ending to talk about how our knowledge about our origins is still growing and there are still questions to answer.
I saw this on the news (CBC) last night.
the science guy was sure excited. (I love his radio show Quirks and Quarks)
Bob Macdonald. He talked to my son's class (grade 5/6 gifted class) about science on Monday and they've got a class picture with him. Showed them video of him riding the "vomit comet". I've been listening to and watching him for years and he's definitely one of the better science journalists out there right now.
But I feel bad for porr old fossilied Lucy who now loses her treasured spot as earliest fossil.
She's still another important link in the tree and is plenty important in her own right. I'm sure even her discoverers realized that she wasn't the end of the trail. Ardi may not be either. That's what I love about science, especially in this area: you never know where the road may go next.
Mendalla
chansen
Posted on: 10/02/2009 20:48
oui started the thread on: 10/01/2009 21:27
Aquaman posted the following on: 10/02/2009 16:24
If a different-animal-evidence has been found, I view that as quite wonderful. I believe it to be yet one more thing that God chose to create. I reject the concept that it is years-old-millions, and that it is any ancestor-to-humans-kind. I continue to praise God for what I value as his glorious creation.
It took almost 19 hours for someone to dismiss careful scientific research by first-hand analysis with our best instruments by our best minds, that builds upon decades of study and progress, because it all conflicts with a very old book that says God made everything in 6 days.
I'm impressed by the 19 hour delay.
oui
Posted on: 10/02/2009 21:00
If a different-animal-evidence has been found, I view that as quite wonderful. I believe it to be yet one more thing that God chose to create. I reject the concept that it is years-old-millions, and that it is any ancestor-to-humans-kind. I continue to praise God for what I value as his glorious creation.
Aquaman, did you read the accompanying 11 research papers detailing the anatomical reasons for linking Ardi to humans before reaching this conclusion?
The expanded research about its lack of large canine teeth, like us and unlike chimps, is fascinating.
oui
Posted on: 10/02/2009 21:18
InannaWhimsey, thanks for the link, I came across that article quite awhile ago, and forgot where it was. Very, extremely interesting site.