Zimmer reports that back in 1964, researchers found the skull of a Homo erectus in the Lantian area of the Shaanxi Province, which at the time they placed at around 1.15 million years. When researchers revisited the Lantian site in the early 2000s, however, they determined that the layer the skull came from was older — about 1.63 million years old. They also noticed what appeared to be stone tools embedded 200 feet up in a cliff face, smithsonianmag.com reported.
That observation led to 13 years of painstaking excavations. During that time, the team found that various human ancestors occupied the site in Shangchen's southern Chinese Loess Plateau between 1.26 and 2.12 million years ago.
According to their study, published in the journal Nature, the researchers uncovered 80 stone artifacts found in 11 layers of soil deposited when the climate was warm and wet. They also uncovered 16 artifacts in six layers that date to a time when the climate conditions were colder and drier.
Most importantly, they were able to date the layers of soil using a technique called paleomagnetism by looking at certain minerals which align with the Earth's magnetic field, which occasionally flip flops. The oldest artifacts were found in a layer sandwiched between rock formed 2.14 million years ago and 1.85 million years ago. Based on their position, the researchers estimate six of the tools are 2.12 million years old, making them the oldest stone tools found outside Africa.
The finding doesn't necessarily indicate that it was Homo erectus which made it to China faster than previously thought. It's believed Homo erectus hadn't even evolved by this point, so the artifacts could suggest that a whole other species of hominins expanded east to Asia.
So if it wasn't Homo erectus, who was living in China so long ago? A trove of fossils unearthed in Dmanisi, Georgia, which was the previous oldest hominin site outside of Africa, may shed some light. It included stone tools and, more importantly, part of a skull from a relatively small-brained, short hominin. It's possible that this species or one like it expanded across Eurasia first.
Then again, perhaps we don't have the dates for Homo erectus nailed yet. "It is entirely possible that Homo erectus occupied China at this time, but given the age of the site, and the possibility that artifacts may be found at even earlier ages, another member of the genus Homo may be occupying Asia, such as a Homo habilis-like ancestor," Petraglia told Michael Greshko at National Geographic.
Rick Potts, the head of the Smithsonian Institution's Human Origins Program, agrees, telling Zimmer that he believes that some Homo erectus-like fossils older than 2.1 million years old may still be found in Africa, making it plausible that a larger human-like hominin made the artifacts found in Lantian.
Just because this species made it out of Africa, however, doesn't mean that they are somehow the ancestor of modern humans. There were likely many species or populations of hominins that left Africa, only to die out somewhere in their journey across the globe.
"Some populations got all the way over to eastern Asia, but we have to imagine that these were small, sort of hunting-and-gathering populations," Petraglia told Robinson Meyer at the Atlantic.
"And while they may have mated across East Asia, it doesn't mean they survived for a long period of time. Some populations might have become isolated, and some might have become extinct."
Some might have even gone on to develop into other species, like the Indonesian Homo floresiensis who may have evolved much earlier than first thought, according to recent research.
It's unlikely this will be the only discovery about early humans to come out of China. While most paleoanthropologists have spent most of their time and resources searching for hominins in Africa, an increase in fieldwork in China and the rest of Asia is sure to dig up a few more surprises about our increasingly complex human family tree.