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.
