Oldest human fossils dated as 200,000yrs old

Thursday, February 17, 2005 Two sets of remains, one a near complete set, the other just a skull, found in Ethiopia forty years ago, have been dated using potassium-argon dating, as the oldest human remains yet discovered at 195,000 years old. Remains from Herto, Ethiopia held the previous record of 160,000 years.

The findings, published in the February 17 issue of the journal Nature, show the remains Omo I and II, approach what geneticists believe is the age of the human race — 200,000 years. Due to geological activity in the region, this number may not be accurate; it is feasible that the fossils are as young as 104,000.

The uncertainty is due to the method by which they were dated from the known geological age of surrounding rock. The exact dig location where the fossil remains had been excavated in 1967 needed to be relocated.

It was determined that Omo I and II were buried in the lowest sedimentary layer, dubbed Member 1, of the 100-meter-thick Kibish rock formation, near the Omo River. By searching for datable material in that layer, and then dating it using the potassium-argon method, a research team was able to estimate an age for the fossils by association.

The date found agrees with findings from genetic studies on modern human populations, which use extrapolation to determine a date for the earliest modern humans.

In the same Member 1 sediment layers, were found additional Omo I bones, animal fossils, and stone tools.

"Those who believe that there is widely scattered evidence of 'modern' behavior going back 200,000 years in Africa will be delighted that modern human anatomy also goes back that far," according to study co-author John Fleagle, a physical anthropologist at Stony Brook University in New York.

When comparing the two sets of fossils, there is an anatomical difference between them. Omo II is much more primitive in appearance, while Omo I more resembles modern anatomy. Their existence in the same location in the same geological timeframe, may change the way scientists believe humans evolved.

Chris Stringer, director of the Human Origins Group at the Natural History Museum in London: "Given what we see in larger fossil samples from other regions, we may need to accept that African populations showed large [physical-form] variation at this time."

Sources

CBC News. "Our earliest ancestors get older" — Canadian Broadcasting Corporation, February 16, 2005
Hillary Mayell. "Oldest human fossils identified" — National Geographic Society, February 16, 2005

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