But it was painstakingly slow work, because the researchers wanted to make a compelling case that these really were tools made by hominins — and that they really were ancient.
“We wanted to make it watertight and bombproof,” said Dr. Dennell.
In the new study, he and his colleagues argue that the stones could not have been naturally damaged. The surrounding rock had formed from grassland soil, which didn’t contain stones the size and shape of the tools.
Instead, the researchers argue, the hominins at Lantian must have traveled miles away to mountain streams to find the right stones for making tools. The hominins carried the tools with them to use in gathering food, perhaps using sharp-edged stones to carve meat from carcasses.