Our understanding of when Homo erectus, commonly known as ‘Peking Man’, migrated into Asia has been challenged by a new analysis published in Nature this week. This research, using a new method to date the bones of Homo erectus representatives found in the Zhoukoudian caves, near Beijing, indicates that Peking Man may be 200,000 years older than previously thought.
The Peking Man fossils were discovered in the 1920s during cave excavations in Zhoukoudian, and later classified as the species Homo erectus. The cave site — the largest single source of Homo erectus fossils in the world — has yielded the remains of at least 40 individuals, including six fairly complete hominin cranium and bones. It has also yielded some 17,000 stone artifacts and so provides a unique window on the life of Homo erectus in the region’s temperate north.
Scientists have used various techniques to date the finds their accuracy has been limited by a lack of suitable methods for cave deposits. Guanjun Shen from Nanjing Normal University, China, and colleagues used a relatively new dating method based on the radioactive decay of aluminum (Al) and beryllium (Be) isotopes in quartz grains. Using this method, known as ‘burial dating’, the researchers were able to compare the differential decay in radiation levels of the unstable isotopes 26Al and 10Be in quartz grains exposed to cosmic radiation at the land surface, and in sediments shielded from cosmic radiation by deep burial in a cave.
Shen and team were also able to use the method to obtain a more precise age for the fossils. The finds are now dated to around 750,000 years old — some 200,000 years older than previous estimates. This analysis indicates a hominin presence in the area through glacial–interglacial cycles.
In a related News & Views article, Russell Ciochon and Arthur Bettis from Iowa University, USA, suggest that the technique offers potential in a range of situations where dating has been difficult. Thus, while these latest results help to build a more reliable chronology of human evolution in East Asia, they also herald new opportunities to advance our understanding of ancient migrations of Homo erectus across east Asia.
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