Early hominids first walked on two legs in woods, not on open grasslands

October 9th, 2009 - 1:30 pm ICT by ANI  

Washington, October 9 (ANI): In a new research, scientists have determined that early hominids first walked on two legs in the woods, not on the open, grassy savanna.

University of Illinois anthropology professor Stanley Ambrose and his team carried out the research.

Using carbon isotope analyses on the oldest known, nearly complete skeleton of a hominid, Ambrose indicated that Ardipithecus ramidus took its first steps toward bipedalism not on the open, grassy savanna, but in a wooded landscape.

Ambrose analyzed the teeth of two-dozen mammal species found in the same ancient soil layer as Ardipithecus in order to help reconstruct its environment.

“This species was not a savanna species like Darwin proposed,” said Ambrose.

This creature, believed to be an early ancestor of the human lineage, lived in Ethiopia some 4.4 million years ago.

Ambrose analyzed stable carbon isotope ratios in the soil in which the bones of 36 Ardipithecus individuals were found.

He also analyzed the teeth of five Ardipithecus individuals and 172 teeth of two-dozen mammal species found in the same ancient soil layer.

The fossil-bearing layer, in the Afar Rift region of northeastern Ethiopia, spans a broad arc about 9 kilometers long.

The carbon isotope ratios of the soils indicated that in the time of Ardipithecus the landscape varied from woodland in the western part of the study zone to wooded grassland in the east.

None of the Ardipithecus specimens were found in the grassy eastern part of the arc.

“Fossils of many species are common all the way across the landscape,” Ambrose said. “But this species is missing in action from the east side of the distribution,” he added.

“On the west we find lots of Ardipithecus fossils and they’re associated with a lot of woodland and forest animals,” he said. “And then there’s a break; Ardipithecus and most of the monkeys that live in trees disappear, and grass-eating animals become more abundant,” he added.

The carbon isotope ratios of the Ardipithecus teeth also tell the story of a woodland creature.

“The diet of the Ardipithecus is much more on the woodland and forest side,” said Ambrose. “It’s got a little bit more of the grassland ecosystem carbon in its diet than that of a chimpanzee but much less than its fully bipedal savanna-dwelling descendents, the australopithecines,” he added.

This evidence, along with the anatomical studies indicating that Ardipithecus could walk upright, but also grasped tree limbs with its feet, suggests that this early hominid took its first steps on two legs in the forest long before it ventured very far into the open grassland. (ANI)

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