Our earliest ancestors get older
Wed, 16 Feb 2005
CBC News
LONDON - Two controversial skulls unearthed nearly 40 years ago in Ethiopia have now been confirmed as the oldest modern human remains.
Using today's dating techniques, the fossils are estimated to be around 195,000 years old – placing them in the time at which modern humans are thought to have emerged.
When the fossils, called Omo I and Omo II, were first discovered in 1967 by anthropologist Richard Leakey and his team, scientists disagreed over if they were the same age.
Some researchers argued the skull and skeletal bones of Omo I had more distinctly "modern" features than its skull-only companion.
Back then, Leakey's team called both specimens Homo sapiens with a tentative age of 130,000 years.
Now, geologist Ian McDougall of the Australian National University in Canberra and his colleagues in the U.S. have used a new approach that may help quell the dating debate.
In Thursday's issue of the journal Nature, researchers say there's evidence both fossils came from the same layer of sedimentary rock.
The skulls were found in the Kibish Formation, an outcrop about 100 metres deep near the Omo River in southwestern Ehiopia.
As in carbon dating, the team looked at the rate of decay of argon isotopes. This atomic "clock" reveals when the skulls were deposited in the sediment.
The answer: 195,000 years ago, give or take 5,000 years.
Some bones found in 2001 are related to fossils discovered earlier.
Given the uncertainty of dating material from such a tectonically active region of Africa, the team acknowledged the skulls could be as young as 104,000 years old.
"Omo I and Omo II [are] the oldest anatomically modern human fossils yet discovered," the study's authors said.
The new dating helps align the fossil record with genetic studies that suggest Homo sapiens arose about 200,000 years ago.
Most anthropologists say Homo sapiens emerged in East Africa about 200,000 to 250,000 years ago, migrated north and then east to the rest of the world.
Wed, 16 Feb 2005
CBC News
LONDON - Two controversial skulls unearthed nearly 40 years ago in Ethiopia have now been confirmed as the oldest modern human remains.
Using today's dating techniques, the fossils are estimated to be around 195,000 years old – placing them in the time at which modern humans are thought to have emerged.
When the fossils, called Omo I and Omo II, were first discovered in 1967 by anthropologist Richard Leakey and his team, scientists disagreed over if they were the same age.
Some researchers argued the skull and skeletal bones of Omo I had more distinctly "modern" features than its skull-only companion.
Back then, Leakey's team called both specimens Homo sapiens with a tentative age of 130,000 years.
Now, geologist Ian McDougall of the Australian National University in Canberra and his colleagues in the U.S. have used a new approach that may help quell the dating debate.
In Thursday's issue of the journal Nature, researchers say there's evidence both fossils came from the same layer of sedimentary rock.
The skulls were found in the Kibish Formation, an outcrop about 100 metres deep near the Omo River in southwestern Ehiopia.
As in carbon dating, the team looked at the rate of decay of argon isotopes. This atomic "clock" reveals when the skulls were deposited in the sediment.
The answer: 195,000 years ago, give or take 5,000 years.
Some bones found in 2001 are related to fossils discovered earlier.
Given the uncertainty of dating material from such a tectonically active region of Africa, the team acknowledged the skulls could be as young as 104,000 years old.
"Omo I and Omo II [are] the oldest anatomically modern human fossils yet discovered," the study's authors said.
The new dating helps align the fossil record with genetic studies that suggest Homo sapiens arose about 200,000 years ago.
Most anthropologists say Homo sapiens emerged in East Africa about 200,000 to 250,000 years ago, migrated north and then east to the rest of the world.
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