A Homo erectus skull found in China dates to about 639,000 years ago, while a second skull discovered nearby is estimated at roughly 652,000 years ago, researchers report. The findings revise the ages of fossils unearthed near Nanjing in 1993 and suggest the two lived during the same broad period.
The study, published in Quaternary Science Reviews, examined material from Hulu Cave in eastern China. Scientists dated deposits linked to the fossils, called Nanjing Cranium I and Nanjing Cranium II, using several methods to resolve conflicting earlier estimates.
Cranium I, classified as Homo erectus, came from a fossil-rich chamber called “Small Cave.” Tests of teeth found in the same layer produced an age estimate of 639,000 years, with a margin of 27,000 years. Deposits thought to be associated with Cranium II were dated to 652,000 years, plus or minus 26,000 years.
How scientists dated the Homo erectus skull in China
Researchers used uranium-series dating on cave minerals and combined electron spin resonance with uranium-series dating on fossil teeth. The methods helped establish when the material surrounding the skulls was deposited.
Previous studies offered sharply different dates. Tests of teeth from “Small Cave” suggested an age of about 350,000 years, but a mineral layer covering the fossil-bearing deposits indicated that Cranium I was at least 530,000 years old.
The latest tests confirmed that the overlying mineral layer formed about 530,000 years ago. Dating of teeth from the same fossil-bearing layer placed Cranium I at about 639,000 years, providing a more precise estimate.
The second skull posed another problem. Workers’ accounts left uncertainty over whether it came from “Small Cave” or a passage known as the “Artificial Corridor.” The new tests dated fossil-bearing deposits from the corridor to about 652,000 years ago, closely matching the age calculated for the smaller chamber.
Why the second Nanjing skull still raises questions
The similar dates strengthen the case that the two skulls belong to the same general period, though the study does not settle whether they represent the same human species.
Cranium I includes portions of the skullcap and face and has long been assigned to Homo erectus. Cranium II is more damaged. Earlier assessments linked it to Homo erectus, while another study suggested features closer to archaic Homo sapiens.
The researchers say the revised ages provide a basis for examining that disagreement again. The results also place the cave remains within the early Middle Pleistocene, an important period in the history of ancient human populations across East Asia.
Together, the findings offer a firmer timeline for the Homo erectus skull in China and new grounds for studying the identity of the second fossil.
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