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Diet Diverged In Earliest Human Ancestors
Posted: Wednesday, December 27, 2000
FAYETTEVILLE, Ark. -- Dietary diversity distinguished the diets of our earliest human ancestors, starting a trend that eventually led to the ability of human beings to colonize different types of terrain all over the world, according to two researchers.
Peter Ungar, associate professor of anthropology at the University of Arkansas, and Mark Teaford, professor of cell biology and anatomy at Johns Hopkins University School of Medicine, report their findings in the Dec. 5 issue of the Proceedings of the National Academy of Sciences.
Ungar and Teaford used dental and jaw data from Ardipithecus ramidus, Australopithecus anamensis, Australopithecus afarensis and Australopithecus africanus, Pliocene hominids that date back 2.3 to 4.4 million years ago. They looked at tooth size, tooth shape, tooth enamel structure, dental microwear and mandibular biomechanics of the fossils, most of which date back to a time before stone tools, before culture and before meat was introduced to the diet.
"No one has looked at diet variability within this group," Ungar said. "Until now, we had no idea of what happened from the standpoint of diet in the first half of human evolution."
The researchers found that even the dental fossils of the oldest human ancestor studied -- Ardipithecus ramidus -- showed signs of a generalized diet. A few hundred thousand years later, the fossils show larger teeth with thicker enamel, and a million years later the fossils sport larger teeth and heavier jaws suited for heavy chewing of hard, brittle foods. But microscopic marks on the teeth also indicate that the hominids had not lost the ability to eat soft, tough foods, like fruit.
"You're seeing an ability to broaden the diet," Ungar said.
This generalized diet became crucial 2.5 million years ago, when our human ancestors split from the specialized forms of hominid species that eventually died out. Researchers speculate that the hominids with a more varied diet were able to survive environmental changes, while the specialists could not adapt quickly enough.
Until now, there was no evidence of dietary changes in the first half of human evolution. Ungar and Teaford's research shows that diets were changing throughout the evolution of our human ancestors, from the time soon after they split from the apes.
"The specialists and generalists branch off, but both stem from a trend that started 5 million years ago," Ungar said.
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Posted: Monday, December 4, 2000
(ABC News) N A I R O B I, Kenya, Dec. 4 — French and Kenyan scientists have unearthed fossilized remains of mankind’s earliest known ancestor that predate previous discoveries by more than 1.5 million years, the team announced today.
They said the discovery of “Millennium Man,” as the creature has been nicknamed, could change the way scientists think about evolution and the origin of species.
The first remains were discovered in the Tugen hills of Kenya’s Baringo district on Oct. 25 by a team from College de France in Paris and the Community.
Since then, the scientists have unearthed distinct body parts belonging to at least five individuals, both male and female.
"Not only is this find older than any else previously known, it is also in a more advanced stage of evolution," palaeontologist Martin Pickford told a news conference.
"It is at least 6 million years old, which means it is older than the [previously oldest] remains found at Aramis in Ethiopia, which were 4.5 million years old."
"Lucy," the skeleton of Australopithicus afarensis found in Ethiopia in 1974, is believed to have lived around 3.2 million years ago.
An almost perfectly fossilized left femur shows the much older Millennium Man already had strong back legs which enabled it to walk upright — giving it hominid characteristics which relate it directly to man.
A thick right humerus bone from the upper arm suggests it also had tree-climbing skills, but probably not enough to "hang" from tree branches or swing limb to limb.
The length of the bones show the creature was about the size of a modern chimpanzee, according to Brigitte Senut, a team member from the Museum of Natural History in Paris. But it is the teeth and jaw structure which most clearly link Millennium Man to the modern human.
It has small canines and full molars — similar dentition to modern man and suggesting a diet of mainly fruit and vegetables with occasional opportunistic meat-eating. More
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