Migration of early man clarified?

It's been said that the scraps of fossil evidence for human evolution are so scant they would barely cover a pool table. The step-by-step footprints of how humans became humans may be buried for all time.

But the "story" that connects the dots of all the fragments and shards seems to change every time a new piece of the puzzle is discovered and tries to fit in.

The same is true of the trail the genus or evolutionary group Homo (of which we, as Homo sapiens, are part) followed when it left Africa and dispersed across Eurasia and beyond. Evidence of a humanlike creature discovered in the Georgian town of Dmanisi has been the crown jewel of that out-of-Africa story for years, pegging the estimated time of departure at 1.8 million years ago.

The next oldest — two incisor teeth believed to be from a Homo erectus in Yuanmou in South China — are 1.7 million years old.

Hominin (humans and close ancestors) fossil evidence from Gongwangling and the Sangiran dome in Java and artifacts from Majuangou and Shangshazui suggest that by 1.6 million years ago Asia probably had a robust and restless population of early humans.

Now a newly announced collection of stone tools unearthed in the Loess Plateau, north of China's Qinling mountains, throws a monkey wrench in the story once again.

The headline read: "Discovery in China hints that humanlike species left Africa 250,000 years earlier than suspected."

The excavation site featured 17 layers of earth dating from 1.26 million to 2.12 million years ago, a veritable filing cabinet of prehistory.

The 96 artifacts recovered — mostly chipped rocks and hammer stones — imply that "hominins left Africa earlier than indicated by the evidence from Dmanisi (Georgia)", the authors write in the journal Nature.

"We were very excited," expedition leader Zhaoyu Zhu, a professor at the Guangzhou Institute of Geochemistry, told Time magazine. "One of my colleagues noticed a stone embedded in a steep outcrop. After a short while, more artifacts were found — one after another."

Archaeologist and stone tool expert Sonia Harmand of Stony Brook University in New York said, "This could be, frankly, one of the most important sites in the world."

This story is getting confusing. Almost 20 years ago, the fossil site at the Renzidong (Renzi Cave) in Anhui province yielded stone tools and animal bones dated 2.25 million years ago, suggesting that Homo erectus was roving out of Africa and across Asia 400,000 years earlier than earlier than previously thought.

Some Chinese scientists at the time even theorized there might have been an evolution of H. erectus parallel to the one in Africa.

After two years of digging at the Renzidong site, a steep fissure that, it's believed, animals were chased into then slaughtered, scientists had discovered remains of 60 species of animals, including the elephantlike Sinoamastadon, an ancient tapir and the monkey Procynocephalus, showing that "Renzidon was open briefly between 2.5 and 2 million years ago," University of Iowa professors Russell Ciochon and Roy Larick wrote in Archaeology at the time.

"Early hominins were ferociously migratory, and this led to the worldwide diaspora of our species, H. sapiens," they wrote, "Early humans repeatedly passed between Africa and Asia, and their movements correspond to those of other large mammals."

If that doesn't muddy the waters enough, an anthropologist at William Paterson University cast a show of doubt on the new find. "I am skeptical," Geoffrey Pope told Time. "I suspect this discovery will change very little."

Sometimes nature can shape stones in a way that makes them look handmade.

Contact the writer at chrisdavis@chinadailyusa.com.