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youtube video about Ardi
http://www.youtube.com/watch?v=-sUM7Pga33M http://www.washingtonpost.com/wp-dyn/content/article/2009/10/01/AR2009100103432_pf.html http://news.nationalgeographic.com/news/pf/85209423.html http://news.yahoo.com/s/ap/20091001/ap_on_sc/us_sci_before_lucy http://www.wbur.org/news/npr/113387960 WASHINGTON POST "Ardi' May Rewrite the Story of Humans 4.4 Million-Year-Old Primate Helps Bridge Evolutionary Gap By Joel Achenbach Washington Post Staff Writer Friday, October 2, 2009 Ardi lived 4.4 million years ago in the woodlands of East Africa. She spent most of her time in the trees. She stood about 4 feet tall, weighed 110 pounds, and had long arms, short legs, and a grasping big toe that was perfect for clambering branch to branch. She ate in the trees, raised her offspring in the trees, slept in the trees. But sometimes she came down to the ground, and stood upright. She could walk on two legs. She was, in a sense, taking baby steps on a journey that would change the world. "Ardi" is the nickname given to a shattered skeleton that an international team of scientists painstakingly excavated from the Ethiopian desert, analyzed over the course of 15 years, and declared Thursday to be a major breakthrough in the study of human origins. Ardi lived more than a million years before "Lucy," a much-celebrated, 3.2 million-year-old fossil of an early human progenitor found just 45 miles away. If the scientists are correct, Ardi and her kind were the ancestors of our ancestors. She was a transitional figure, almost a hybrid -- a tree creature who could carry food in her arms as she explored the woodland floor on two legs. The skeletal remnants of Ardi were recovered along with bones from at least 35 other members of a species that the scientists call Ardipithecus ramidus. Their arduous investigation had incited grumbling in a scientific community that had grown impatient to find out what exactly had been found in the silty clay of Ethiopia. The answers are dramatic, detailed in 11 papers published Thursday in the online edition of the journal Science and discussed in dual press conferences in Washington and Addis Ababa, Ethiopia. The discovery of Ardi "further confirms that Ethiopia is the cradle of humankind," said Yohannes Haile-Selassie, the paleontologist who found the first two bones of Ardi in 1994. Human origins is a field with high stakes and small bones, and the elaborate roll-out of the new research probably will trigger debate about the message contained in fossils so fragile they had to be excavated with dental picks and porcupine quills. "It was a sort of a time capsule from 4.4 million years ago with contents that nobody had ever seen before," said Tim White, a University of California at Berkeley paleoanthropologist who led the Ardi research team. "We worked for years at opening that time capsule by collecting every shred of evidence that we could find." The scientists who found Ardi do not contend that she necessarily evolved into Lucy. The human line of primates could have splintered, with some species turning into genetic dead ends. Lucy's line of primates could have diverged from Ardi's line long before Ardi lived. Even so, White said he believes that his team has documented an evolutionary sequence that shows, at the genus level, where people came from. Ardipithecus, then Australopithecus, then Homo. Lucy, a member of the species Australopithecus afarensis, was a small-brained primate that had fully adapted to a bipedal life and had expanded her habitat beyond the forest into the savannah of Africa. Unlike Ardi, she lacked the grasping big toe. Ardi and Lucy had different teeth, with Lucy's enlarged molars more adapted to a wide-ranging diet on the savannah. "Ardi tells us twice as much as Lucy did. We have hands and feet, a more complete environment, a more complete skeleton, it's older, it's more primitive, it shows us the process of transformation from common ancestor to hominid," said C. Owen Lovejoy, an anthropologist at Kent State University who was part of the Ardi team. White and colleagues found the first signs of the new species in what is known as the Middle Awash, a site in a treeless desert that 4 million years ago would have been much wetter, teeming with birds, reptiles and primates and thickly covered with fig and palm trees. On Nov. 5, 1994, Haile-Selassie, then a Berkeley graduate student and now a curator at the Cleveland Museum of Natural History, found two finger bones. Further digging turned up scraps of a pelvis, feet, hands, chips from a skull. By the end of three years of digging, the scientists realized they'd found a paleontological treasure, a partial skeleton, broken up and ravaged by time. This was Ardi. It was not until Thursday, after a decade and a half of work in the field and the lab, that White and his colleagues produced the first comprehensive analysis of the new species. The original fossils are being housed in a museum in Ethiopia. "It's just a treasure-trove of surprises," Lovejoy said. The origin of the human species via evolution from earlier primates is beyond scientific dispute. Field work over the past century has shown that the human line originated in Africa, and the fossil findings have been bolstered by laboratory analysis of the genetic codes of humans, chimpanzees and other primates. The fine details of human origin, however, become sketchier, and more subject to interpretation and debate, as the researchers dig deeper into the past and the fossils become scarcer. Scientists continue to search for the "last common ancestor," sometimes abbreviated as the LCA. This is the creature to which both modern humans and modern chimpanzees can trace their ancestry. Many scientists think the common ancestor lived at least 7 million years ago. The new research on Ardi suggests that this ancestor didn't look nearly as much like a modern chimpanzee as had been previously suspected. Rather, the ancestor would have looked more like Ardi. This suggests that chimpanzees, far from being time machines for visiting the distant past, have themselves evolved significantly, including developing such skills as suspending from branches and knuckle-walking. "The common ancestor looked like Ardi. It's the chimp and gorilla that have evolved enormously, not hominids. Hominids have concentrated their evolution in two things -- upright walking and brain. Everything else is pretty primitive," Lovejoy said. In Ardi's species, the males are not significantly different in size from the females. The males also lack the dagger-like teeth that male chimps use to fight one another for access to ovulating females. Lovejoy argues that this is a sign of a different social organization. The males, he argues, pair-bonded with females. Lovejoy sees male parental investment in the survival of offspring as a hallmark of the human lineage. David Pilbeam, a Harvard paleontologist, noted that there has been some impatience in the scientific community as White and his team conducted the analysis of the new species, but he suggested that the wait was worth it: "This is an extraordinary achievement, of discovery, recovery, reconstitution, description and analysis, which will keep many others busy for at least another 15 years." Ardi did not look like a human by any stretch. And there is no way to read her mind and measure her sense of self, her awareness of her place in the universe. But if the scientists are correct, her path in life proved to be fruitful over time, and the planet witnessed the rise of a new animal that could run on two legs, invent tools, tame fire, and perhaps eventually -- with much digging and scraping -- decipher its own origin. NATIONAL GEOGRAPHIC Oldest "Human" Skeleton Found--Disproves "Missing Link" Jamie Shreeve Science editor, National Geographic magazine October 1, 2009 Move over, Lucy. And kiss the missing link goodbye. Scientists today announced the discovery of the oldest fossil skeleton of a human ancestor. The find reveals that our forebears underwent a previously unknown stage of evolution more than a million years before Lucy, the iconic early human ancestor specimen that walked the Earth 3.2 million years ago. The centerpiece of a treasure trove of new fossils, the skeleton—assigned to a species called Ardipithecus ramidus—belonged to a small-brained, 110-pound (50-kilogram) female nicknamed "Ardi." (See pictures of Ardipithecus ramidus.) The fossil puts to rest the notion, popular since Darwin's time, that a chimpanzee-like missing link—resembling something between humans and today's apes—would eventually be found at the root of the human family tree. Indeed, the new evidence suggests that the study of chimpanzee anatomy and behavior—long used to infer the nature of the earliest human ancestors—is largely irrelevant to understanding our beginnings. Ardi instead shows an unexpected mix of advanced characteristics and of primitive traits seen in much older apes that were unlike chimps or gorillas (interactive: Ardi's key features). As such, the skeleton offers a window on what the last common ancestor of humans and living apes might have been like. Announced at joint press conferences in Washington, D.C., and Addis Ababa, Ethiopia, the analysis of the Ardipithecus ramidus bones will be published in a collection of papers tomorrow in a special edition of the journal Science, along with an avalanche of supporting materials published online. "This find is far more important than Lucy," said Alan Walker, a paleontologist from Pennsylvania State University who was not part of the research. "It shows that the last common ancestor with chimps didn't look like a chimp, or a human, or some funny thing in between." (Related: "Oldest Homo Sapiens Fossils Found, Experts Say" [June 11, 2003].) Ardi Surrounded by Family The Ardipithecus ramidus fossils were discovered in Ethiopia's harsh Afar desert at a site called Aramis in the Middle Awash region, just 46 miles (74 kilometers) from where Lucy's species, Australopithecus afarensis, was found in 1974. Radiometric dating of two layers of volcanic ash that tightly sandwiched the fossil deposits revealed that Ardi lived 4.4 million years ago. Older hominid fossils have been uncovered, including a skull from Chad at least six million years old and some more fragmentary, slightly younger remains from Kenya and nearby in the Middle Awash. While important, however, none of those earlier fossils are nearly as revealing as the newly announced remains, which in addition to Ardi's partial skeleton include bones representing at least 36 other individuals. "All of a sudden you've got fingers and toes and arms and legs and heads and teeth," said Tim White of the University of California, Berkeley, who co-directed the work with Berhane Asfaw, a paleoanthropologist and former director of the National Museum of Ethiopia, and Giday WoldeGabriel, a geologist at Los Alamos National Laboratory in New Mexico. "That allows you to do something you can't do with isolated specimens," White said. "It allows you to do biology." (Related: Rediscover the original Ardipithecus.) Ardi's Weird Way of Moving The biggest surprise about Ardipithecus's biology is its bizarre means of moving about. All previously known hominids—members of our ancestral lineage—walked upright on two legs, like us. But Ardi's feet, pelvis, legs, and hands suggest she was a biped on the ground but a quadruped when moving about in the trees. Her big toe, for instance, splays out from her foot like an ape's, the better to grasp tree limbs. Unlike a chimpanzee foot, however, Ardipithecus's contains a special small bone inside a tendon, passed down from more primitive ancestors, that keeps the divergent toe more rigid. Combined with modifications to the other toes, the bone would have helped Ardi walk bipedally on the ground, though less efficiently than later hominids like Lucy. The bone was lost in the lineages of chimps and gorillas. According to the researchers, the pelvis shows a similar mosaic of traits. The large flaring bones of the upper pelvis were positioned so that Ardi could walk on two legs without lurching from side to side like a chimp. But the lower pelvis was built like an ape's, to accommodate huge hind limb muscles used in climbing. Even in the trees, Ardi was nothing like a modern ape, the researchers say. Modern chimps and gorillas have evolved limb anatomy specialized to climbing vertically up tree trunks, hanging and swinging from branches, and knuckle-walking on the ground. While these behaviors require very rigid wrist bones, for instance, the wrists and finger joints of Ardipithecus were highly flexible. As a result Ardi would have walked on her palms as she moved about in the trees—more like some primitive fossil apes than like chimps and gorillas. "What Ardi tells us is there was this vast intermediate stage in our evolution that nobody knew about," said Owen Lovejoy, an anatomist at Kent State University in Ohio, who analyzed Ardi's bones below the neck. "It changes everything." Against All Odds, Ardi Emerges The first, fragmentary specimens of Ardipithecus were found at Aramis in 1992 and published in 1994. The skeleton announced today was discovered that same year and excavated with the bones of the other individuals over the next three field seasons. But it took 15 years before the research team could fully analyze and publish the skeleton, because the fossils were in such bad shape. After Ardi died, her remains apparently were trampled down into mud by hippos and other passing herbivores. Millions of years later, erosion brought the badly crushed and distorted bones back to the surface. They were so fragile they would turn to dust at a touch. To save the precious fragments, White and colleagues removed the fossils along with their surrounding rock. Then, in a lab in Addis, the researchers carefully tweaked out the bones from the rocky matrix using a needle under a microscope, proceeding "millimeter by submillimeter," as the team puts it in Science. This process alone took several years. Pieces of the crushed skull were then CT-scanned and digitally fit back together by Gen Suwa, a paleoanthropologist at the University of Tokyo. In the end, the research team recovered more than 125 pieces of the skeleton, including much of the feet and virtually all of the hands—an extreme rarity among hominid fossils of any age, let alone one so very ancient. "Finding this skeleton was more than luck," said White. "It was against all odds." Ardi's World The team also found some 6,000 animal fossils and other specimens that offer a picture of the world Ardi inhabited: a moist woodland very different from the region's current, parched landscape. In addition to antelope and monkey species associated with forests, the deposits contained forest-dwelling birds and seeds from fig and palm trees. Wear patterns and isotopes in the hominid teeth suggest a diet that included fruits, nuts, and other forest foods. If White and his team are right that Ardi walked upright as well as climbed trees, the environmental evidence would seem to strike the death knell for the "savanna hypothesis"—a long-standing notion that our ancestors first stood up in response to their move onto an open grassland environment. Sex for Food Some researchers, however, are unconvinced that Ardipithecus was quite so versatile. "This is a fascinating skeleton, but based on what they present, the evidence for bipedality is limited at best," said William Jungers, an anatomist at Stony Brook University in New York State. "Divergent big toes are associated with grasping, and this has one of the most divergent big toes you can imagine," Jungers said. "Why would an animal fully adapted to support its weight on its forelimbs in the trees elect to walk bipedally on the ground?" One provocative answer to that question—originally proposed by Lovejoy in the early 1980s and refined now in light of the Ardipithecus discoveries—attributes the origin of bipedality to another trademark of humankind: monogamous sex. Virtually all apes and monkeys, especially males, have long upper canine teeth—formidable weapons in fights for mating opportunities. But Ardipithecus appears to have already embarked on a uniquely human evolutionary path, with canines reduced in size and dramatically "feminized" to a stubby, diamond shape, according to the researchers. Males and female specimens are also close to each other in body size. Lovejoy sees these changes as part of an epochal shift in social behavior: Instead of fighting for access to females, a male Ardipithecus would supply a "targeted female" and her offspring with gathered foods and gain her sexual loyalty in return. To keep up his end of the deal, a male needed to have his hands free to carry home the food. Bipedalism may have been a poor way for Ardipithecus to get around, but through its contribution to the "sex for food" contract, it would have been an excellent way to bear more offspring. And in evolution, of course, more offspring is the name of the game (more: "Did Early Humans Start Walking for Sex?"). Two hundred thousand years after Ardipithecus, another species called Australopithecus anamensis appeared in the region. By most accounts, that species soon evolved into Australopithecus afarensis, with a slightly larger brain and a full commitment to a bipedal way of life. Then came early Homo, with its even bigger brain and budding tool use. Did primitive Ardipithecus undergo some accelerated change in the 200,000 years between it and Australopithecus—and emerge as the ancestor of all later hominids? Or was Ardipithecus a relict species, carrying its quaint mosaic of primitive and advanced traits with it into extinction? Study co-leader White sees nothing about the skeleton "that would exclude it from ancestral status." But he said more fossils would be needed to fully resolve the issue. Stony Brook's Jungers added, "These finds are incredibly important, and given the state of preservation of the bones, what they did was nothing short of heroic. But this is just the beginning of the story." Look for comprehensive coverage of Ardipithecus ramidus in a future issue of National Geographic magazine. Before Lucy came Ardi, new earliest hominid found By RANDOLPH E. SCHMID, AP Science Writer Randolph E. Schmid, Ap Science Writer Thu Oct 1, 6:33 pm ET 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 29 species 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. ___ On the Net: Science: http://www.sciencemag.org WBUR Move Over, Lucy; Ardi May Be Oldest Human Ancestor By Christopher Joyce Published October 1, 2009 12:07 PM Scientists on Thursday unveiled a fossil human ancestor dating back 4.4 million years — a creature more ancient than the famous fossil "Lucy." And, the scientists say, even more important than Lucy. The team that discovered the fossil, called Ardipithicus ramidus, say it's the closest thing yet found to the common ancestor of both chimps and humans. That common ancestor is thought to have lived about 6 million years ago. From that animal, chimps and other apes evolved in one direction, while our own ancestors, the hominids, evolved through several forms into what we are now. The anthropologists found the bones in Ethiopia, in a desert region called Aramis. Scientists have previously discovered a few teeth and bones of Ardipithicus, dating from 5 to 6 million years ago. But in this case, they have more than 100 bones from 36 individuals, including a partial skeleton of a female whom they've dubbed "Ardi." The area excavated "was a time capsule with contents that nobody had ever seen before," says anthropologist Tim White, of the University of California, Berkeley, and the team co-leader. The skull had been crushed into scores of pieces, says White. But after years of reconstruction work, White says, "what we have is a very small-brained cranium of an early female hominid that is very different from a chimpanzee." That's critical, White says. "People have sort of assumed ... that the last common ancestor was more or less like a chimpanzee." Ardi suggests otherwise — that in fact the earliest known hominid was a "mosaic," with some features like chimps but others like monkeys, such as the feet. Other features are more like the more recent hominid, Lucy (Australopithecus afarensis), such as the teeth. For example, the canine teeth near the front of the mouth in both male and female Ardipithicus are much smaller than a chimp's canines. "It's just a treasure trove of surprises," says C. Owen Lovejoy, one of the leaders of the team and an anthropologist at Kent State University. Take the small canines, he says. A chimp's big, protruding canines — especially the males' — are for fighting or intimidating other males to get access to females, Lovejoy says. Small canines on Ardipithicus suggest a different social strategy. "So females are picking males that are using some other technique to obtain reproductive success, and that technique is probably exchanging food for copulation," Lovejoy says. White and Lovejoy say that the hand and arm bones, as well as bones from the feet and pelvis, suggest that Ardi was able to walk on two legs. But it was probably more comfortable in the trees, though it maneuvered on its palms in a way different from chimps. The team spent almost two decades collecting everything from animal bones to pollen in the region. They conclude that Ardi lived in a lush, wooded environment, not the grassy savanna usually thought to be the habitat of the earliest human ancestors. "This is more important than Lucy," says anthropologist Alan Walker of Penn State University. The number of bones and its greater antiquity give scientists a wealth of new information on this earliest part of human evolution. At the same time, he says, the team's conclusions will draw a lot of skepticism from other scientists. Among the skeptics is Bernard Wood, professor of anatomy at George Washington University. Wood says it could well be that these bones belonged to a creature that evolved outside the line that led to humans — that it was in fact a separate branch of primate evolution that disappeared into a dead end, like so many other forms of ancient life. The scientific community will now get a chance to test the team's conclusions, which are outlined in 11 papers — with 47 authors — in the journal Science. |
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