”Peking Man” 250,000 years older than previously thought

March 12th, 2009 - 12:28 pm ICT by ANI  

London, March 12 (ANI): A new analysis of the Homo erectus fossils popularly known as the ”Peking Man”, found in China’’s Zhoukoudian caves, has determined that it dates back to 770,000 years, which is at least 250,000 years earlier than thought.
According to a report in Nature News, the new date means that this early human ancestor - the first lineage to migrate out of Africa - prospered in an earlier, colder climate, and its physical development in China matched that in Africa, where the species first evolved.
Discovered in 1918, the Zhoukoudian caves near Beijing have yielded surprises for nearly a century.
Layers in the hillside cave system overlooking a river valley have produced some 17,000 stone artefacts and fossils of 50 H. erectus individuals, including six skulls.
The species had a distinctive barrel-shaped torso and stood 145-180 centimeters tall, walking upright in a similar way to modern humans (Homo sapiens).
Now, work by a team of scientists based in China and the US has revealed that the Zhoukoudian cave fossils are about 770,000 years old - much more ancient than previous estimates of 230,000-500,000 years.
The new dates are based on the effects of cosmic rays on aluminium and beryllium isotopes in miniscule quartz grains, which Chinese researchers meticulously selected from sedimentary sand in weeks of painstaking work.
The isotopic method was also applied successfully to three quartz tools.
“This is a catalyst for a new era of re-dating,” said palaeoanthropologist Russell Ciochon of the University of Iowa at Iowa City.
To secure the new dates, Guanjun Shen of Nanjing Normal University collaborated with co-author Darryl Granger at Purdue University in West Lafayette, Indiana.
First, the team had to select clear, white quartz crystals that were buried with the fossils, not grey ones that might have been washed in later.
The dating method is based on the radioactive decay of 26Al and 10Be isotopes.
While they”re on Earth’’s surface, the two isotopes within the quartz are produced at a known ratio through exposure to cosmic radiation.
When sediment buries the quartz, the generation of isotopes by cosmic rays nearly stops.
The researchers dated the fossils by determining the isotopic content of the quartz and calculating backwards to work out the ratio of the two isotopes when the quartz was buried.
More precise dates will fill in gaps about the migrations of H. erectus into northern China and to Java in Indonesia, which occurred at least 1.6 million years ago.
H. erectus evolved about 2 million years ago in equatorial Africa, possibly surviving to 50,000 years ago in Indonesia. (ANI)

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