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Ancient Skeleton May Rewrite Earliest Chapter of Human EvolutionScience magazine presents 11 papers, by a multinational team of 47 researchers, describing an early hominid species, Ardipithecus ramidus. These 4.4 million year old hominid fossils sit within a critical early part of human evolution, and cast new and sometimes surprising light on the evolution of human limbs and locomotion, the habitats occupied by early hominids, and the nature of our last common ancestor with chimps.
UK Daily Mail—She lived at the dawn of a new era, when chimps and people began walking (or climbing) along their own evolutionary trails. This is Ardi – the oldest member of the human family tree we’ve found so far.
Short, hairy and with long arms, she roamed the forests of Africa 4.4million years ago.
Her discovery, reported in detail for the first time today, sheds light on a crucial period when we were just leaving the trees. Some scientists said she could provide evidence that our ancestors first started walking upright in the pursuit of sex.
Conventional wisdom says our earliest ancestors first stood up on two legs when they moved out of the forest and into the open savannas. But this does not explain why Ardi’s species was bipedal (able to walk on two legs) while still living partly in the trees.
Owen Lovejoy from Kent State University said the answer could be as simple as food and sex.
He pointed out that throughout evolution males have fought with other males for the right to mate with fertile females. Therefore you would expect dominant males with big fierce canines to pass their genes down the generations.
But say a lesser male, with small stubby teeth realized he could entice a fertile female into mating by bringing her some food? Males would be far more successful food-providers if they had their hands free to carry home items like fruit and roots if they walked on two legs.
Mr Lovejoy said this could explain why males from Ardi’s species had small canines and stood upright – it was all in the pursuit of sex.
He added that it could also suggest that monogamous relationships may be far older than was first thought.
New York Times/John Noble Wilford—The Ardipithecus specimen, an adult female, probably stood four feet tall and weighed about 110 pounds, almost a foot taller and twice the weight of Lucy. Its brain was no larger than a modern chimp’s. It retained an agility for tree-climbing but already walked upright on two legs, a transforming innovation in hominids, though not as efficiently as Lucy’s kin.
Ardi’s feet had yet to develop the arch-like structure that came later with Lucy and on to humans. The hands were more like those of extinct apes. And its very long arms and short legs resembled the proportions of extinct apes, or even monkeys.
Tim D. White of the University of California, Berkeley, a leader of the team, said in an interview this week that the genus Ardipithecus appeared to resolve many uncertainties about “the initial stage of evolutionary adaptation” after the hominid lineage split from that of the chimpanzees. No fossil trace of the last common ancestor, which lived some time before six million years ago, according to genetic studies, has yet come to light.
The other two significant stages occurred with the rise of Australopithecus, which lived from about four million to one million years ago, and then the emergence of Homo, our own genus, before two million years ago. The ancestral relationship of Ardipithecus to Australopithecus has not been determined, but Lucy’s australopithecine kin are generally recognized as the ancestral group from which Homo evolved.
Science—Until now, the oldest known skeleton of a human ancestor was Lucy, who proved in one stroke that our ancestors walked upright before they evolved big brains. But at 3.2 million years old, she was too recent and already too much like a human to reveal much about her primitive origins. As a result, researchers have wondered since her discovery in 1974, what came before her–what did the early members of the human family look like?
Now, that question is being answered in detail for the first time. A multinational team discovered the first parts of the Ar. ramidus skeleton in 1994 in Aramis, Ethiopia. At 4.4 million years old, Ardi is not the oldest fossil proposed as an early hominin, or member of the human family, but it is by far the most complete–including most of the skull and jaw bones, as well as the extremely rare pelvis, hands, and feet. These parts reveal that Ardi had an intermediate form of upright walking, a hallmark of hominins, according to the authors of 11 papers that describe Ardi and at least 35 other individuals of her species. But Ardi still must have spent a lot of time in the trees, the team reports, because she had an opposable big toe. That means she was probably grasping branches and climbing carefully to reach food, to sleep in nests, and to escape predators.
Reuters—Genetics suggest that humans and our closest living relatives, the chimpanzees, diverged 6 million to 7 million years ago, although some research suggests this may have happened 4 million years ago.
“Ardi” is clearly a human ancestor and her descendants did not grow up to be chimpanzees or other apes, the researchers report in Science.
She had an ape-like head and opposable toes that allowed her to climb trees easily, but her hands, wrists and pelvis show she strode like a modern human and did not knuckle-walk like a chimp or a gorilla.
“People have sort of assumed that modern chimpanzees haven’t evolved very much, that the last common ancestor was more or less like a chimpanzee and that it’s been … the human lineage … that’s done all the evolving,” White said.
But “Ardi” is “even more primitive than a chimpanzee,” White said.
So chimps and gorillas do not knuckle-walk because they are more primitive than humans — they have evolved this characteristic that helps them live in their forest homes.
White, Berhane Asfaw of Rift Valley Research Service in Addis Ababa and a large team analyzed all the bones of Ardi and found she might have been more peace-loving than modern chimpanzees. She does not have the long, sharp canines that chimps use to fight, for instance.
And males and females have similar-sized teeth, suggesting more equality than seen among modern apes.
An introduction to Ardi by the Associated Press
A wonderfully informative video by Science magazine
Vodpod videos no longer available.
Fossil hunters in Ethiopia are excavating a mandible, or lower jaw, of Ardipithecus ramidus. A fairly complete skeleton of this individual, nicknamed Ardi, is 4.4-million-years-old. It lived well before and was much more primitive than the 3.2-million-year-old Lucy skeleton, of the species Australopithecus afarensis. Unveiling the Ardi remains this week, scientists said this was the earliest known skeleton of a potential human ancestor. (Photo: Tim White and David L. Brill)
Ardi was discovered in the arid badlands along the middle stretch of the Awash River, near the village of Aramis in Ethiopia. Arid now, it was a cooler, humid woodland in the time of the early hominids Ardipithecus ramidus. (Photo: David L. Brill)
For the past 17 years, scientists collected fragments, some tiny pieces of bone, that represented more than 110 specimens from a minimum of 36 different individuals of the Ardipthecus species, including Ardi. (Photo: David L. Brill)
The few modern Homo sapiens living near the discovery site at Aramis include this Ethiopian goat herder. (Photo: David L. Brill)
Since the first tooth of the new species was picked up in 1992, members of the Middle Awash research project returned year after year to explore the remote site. Here they are on the dusty trail, driving to camp from a survey trip. (Photo: David L. Brill)
The excavation team sits down to breakfast before heading off on another day of fossil hunting in the Middle Awash region of Ethiopia. (Photo: David L. Brill)
An Ethiopian herder, one of the Afar people, moves his stock from the Awash River toward Yardi Lake. (Photo: David L. Brill)
Berhane Asfaw, an Ethiopian paleoanthropologist, works with the local Afars who occupy the lands of the area of the Ardipithecus discoveries. (Photo: David L. Brill)
At the discovery site, Tim D. White, left, a leader of the project, and Yohannes Haile-Selassie crawl over the parched surface looking for the tiniest fossil fragments.(Photo: David L. Brill)
A collection of the fossilized bones that were assembled into the partial skeleton of Ardi. (Photo: David L. Brill)
This is the site, known as Yonas Arm, that yielded fossil evidence of Ardipithecus ramidus. (Photo: David L. Brill)
Scientists have identified both primitive and evolved characteristics of the 4.4-million-year-old Ardi hominid. Here, the hand bones were more like those of earlier apes. (Photo: David L. Brill)
The Ardipithecus specimen, an adult female, probably stood four feet tall and weighed about 120 pounds, almost a foot taller and twice the weight of Lucy. The paleoanthropologists wrote in one of the articles that Ardipithecus was “so rife with anatomical surprises that no one could have imagined it without direct fossil evidence.” (Photo: Tim White 2008, from the Oct. 2 issue of Science)