Ancestral Human Skull Found in China
Kevin Holden Platt in Beijing, China
for National Geographic News
|February 20, 2008|
A human skull tentatively dating back 80,000 to 100,000 years may shed light on a murky chapter of evolutionary history, its discoverers say.
An excavation team led by Chinese archaeologist Li Zhanyang recently found the shattered fossil in the central province of Henan.
China's government-run press was quick to describe the skull as "the greatest discovery in China after Peking Man," but archaeologists and paleoanthropologists say it's a much more modest find.
The Chinese report suggested that the fossil came from a modern human, which would have forced a radical reworking of current theories about when our species first left Africa.
Instead, experts say, the skull likely belongs to a sister or precursor species to modern humans.
While still too early to judge the skull's true significance, the scientists add, it hails from a pivotal evolutionary period, when modern-day humans began to supplant the ancestral human species Homo erectus.
The discovery raises the chances that the two species may have overlapped for some time in China, possibly interbreeding and sharing tools, experts say.
Li—who is now working with Beijing's Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) to reconstruct the fossil—says the skull shows characteristics of both archaic humans and of Homo sapiens.
Cradle of Humanity
A series of half-million-year-old skulls belonging to Homo erectus, collectively called "Peking Man," were found in a massive cave on the outskirts of Beijing in the 1920s and 1930s.
This led many archaeologists to hypothesize that China might be the cradle of humanity, which fit in perfectly with the country's view of itself at the time as the world's "Central Kingdom."
But subsequent digs across Africa unearthed much earlier species, giving rise to the "Out of Africa" model of human origins: Increasingly intelligent humans evolved in Africa, then spread out in widening waves across Asia and Europe.
Although China has ceded its claim to be the center stage of humanity's emergence, some archaeologists have posited Peking Man originally migrated from Africa and then slowly evolved into a modern human in China.
But Chris Stringer, a research leader in the Human Origins Program at the Natural History Museum in London, said that the overwhelming weight of evidence from the fossil record and genetic testing worldwide points to the emergence of Homo sapiens in Africa alone.
"There was only one region, Africa, where a complete evolutionary sequence from Homo erectus to modern humans developed," he said.
"Why Africa?" Stringer asked. "We still don't know, but the large habitable area, even with climatic deterioration, and the inferred large population size and genetic diversity may well be factors."
Based on genetic and migration studies, these modern humans began moving out across Eurasia at least 60,000 years ago and ultimately replaced all earlier species, Stringer said. (See an interactive human migration time line.)
Peking Man Redux
This now-dominant model would have to be reworked if the newly unearthed skull in China were widely agreed to be that of a modern H. sapiens.
"If this is a 'modern' Homo sapiens, with a high rounded skull, divided browridge, and chin, and is 80,000 to 100,000 years old, then it would indicate a very early dispersal of moderns eastwards from Africa and the Middle East," Stringer said.
But Stringer said that the fossil is much more likely to be that of an earlier species.
Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis, Missouri, offered a similar assessment after viewing photos of the Henan skull.
"Based on the anatomy of the skull, with its large projecting browridge, this appears to be close to Peking Man," he said.
The find does raise some interesting possibilities, added Trinkaus, who has worked extensively with scholars from the IVPP to study the 40,000-year-old fossil of a Homo sapiens sapiens excavated near Beijing several years ago.
He and other experts say the discovery of the older Henan skull is important because it increases the possibility that archaic and modern humans coexisted for a time in China, just as they did in Europe.
Trinkaus said that these varying species might sometimes have interbred. The modern human fossil he studied in Beijing featured archaic traits that might have marked it as an inter-human hybrid, he said.
London's Stringer said that if two or more branches of humans co-existed in China, "a whole gamut of population interactions could have occurred, ranging from conflict to possible interbreeding."
Hou Ya-mei, a professor at the IVPP who has excavated and studied stone tools developed by humans in China over the past million years, said that the record of stone technology could be interpreted to support a wide range of encounters between different human species.
"Homo erectus and Homo sapiens might have lived side by side and exchanged stone tool technology," Hou said.
On the other hand, with the development of increasingly sophisticated hand-axes and other stone blades, she added, "it's possible that one group of humans became stronger through better weapons technology."
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