Xinhua Insight: Fossil teeth fill the gaps on human evolution

"Imagining the life of ancient man based on fossil evidence may seem like a romantic pursuit for some, but scientific research is hard work, and not the least bit romantic," said archeologist Cai Yanjun.

Cai is one of China's leading paleontologists and part of a team that has just made some astounding breakthroughs in the study of the origins of modern humans and their primordial dispersal.

"Science is sometimes dry and frustrating," he said, "but the pursuit of truth, and simple faith that the truth will be found, are what motivate all the best scientists."

Cai's team found fossilized teeth in a cave in central China's Hunan Province that indicate an early form of modern homo sapiens living in the region more than 80,000 years ago. The 47 teeth may in fact date back as much as 120,000 years and could be the oldest remains of a completely modern human from east Asia. The Chinese Academy of Sciences (CAS) team published its findings in this month's edition of the journal "Nature."

The teeth found in Daoxian are significantly smaller than those of humans from the the mid and late Pleistocene, indicating that they belong to an earlier epoch. However, the simple biting surface; the short, thin roots; and shape of the crown are typical of modern humans.

It was back in October 1984 when archaeologists from Hunan and scientists the from CAS institute of vertebrate paleontology and paleoanthropology found 24 mammal fossils in a cave in Daoxian County. Years of research led the scientists to concluded that it was very likely that human fossils would be found in the region. The search for human remains restarted in 2011.

TEETHING TROUBLE

Yang Xiongxin was once a simple laborer. He describes himself as "not a well-educated person" without any previous knowledge of archeology: "But I'm an archaeology enthusiast now for sure!"

Yang used to do simple manual work as a bench worker and warehouseman, and started work at Daoxian cultural relic management center in 2006. He was transferred to the research team in 2011, and, although he is no scientist, he was the one to find the first fossil.

Nothing was found at the start of the project after days of digging. The scientists were talking about changing the search area when Yang spoke up: "We had spent such a long time setting up the equipment in the cave, that I said we could not just give up like that. It might not be so easy to find a similar cave in a short time."

Yang suggested going into the cave, where there was less erosion from tens of thousands of years of rain: "Although it was hard to excavate at the location I suggested, I remembered many examples in books of discoveries in similar circumstances."

The team acted on Yang's advice and the first human tooth fossil was found two days later.

"We were so excited after finding the first five. We wrapped each one in silk as though they were treasure."

However, finding more fossils the next year did not make the team more excited. By then the focus of the project changed from simply finding fossils to establishing their history.

GRINDING ON

In October 2011, Cai Yanjun flew from the northwest city of Xi'an -- home to the Terracotta Army, one of the world's most spectacular archeological wonders -- to join the research team.

"I was going to the place where, perhaps, the earliest humans lived," Cai said: "It was definitely worth the long trip."

While other members of the team dug in the cave, Cai's role was basically to "take the small rocks back to the lab to be analyzed." The lab Cai took his "small rocks" to was the world's leading center for radio-isotope dating at the University of Minnesota, but the tests proved inconclusive.

"The fossils we found in the cave were already important in the study of early humans, but it would have been a great pity if we were unable to determine their age," Cai said. All the hard work proved not to have been in vain when, on his third trip to the United States, Cai finally hit pay dirt.

Previous studies, including the classic "Out of Africa" hypothesis, had placed humans with modern features in west Asia and Europe no earlier than 50,000 years ago. Uranium-series dating, carbon-14 testing and "surrounding animal analysis" determined that Cai's fossils were between 80,000 and 120,000 years old.

This was a new angle on the evolution of modern humans, "but it's not enough to overturn the 'Out of Africa' hypothesis," Cai added.

Looking back over the past five years, Cai believes that simple hard work and a never-say-die attitude were the keys to their success.

"It is not romantic at all to just keep repeating the same thing over and over again. But you only have a chance of success if you keep trying and never give up, just like our team," Cai said.

Another project is already underway in Anhui Province. "In the scientific world, you can never know too much," Cai said. Endi