The upper layer contained the remains of typical microblade technology from about 27,000 years ago, further enriching the record of the earliest stage of microblade technology in North China.

Beneath it, in a layer dating back 30,000 years, the critical evidence was found: bladelet cores and related tools.

"When the bladelet core was fully exposed, we had a feeling that this might be the transitional stage we had been looking for," Wang says.

The origin of North China's highly developed microblade technology has long been debated.

This newly discovered bladelet technology sits perfectly between the earlier blade technology found at the site (dated to 45,000 years ago) and the later microblade technology that appeared about 27,000 years ago.

"The significance is immense," says Gao Xing from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences.

"It shows the technological change here was not a sudden replacement from outside, but a gradual, internal evolution."

Xinmiaozhuang offers more than just a timeline of toolmaking.

Over 100 personal ornaments, primarily beads made from ostrich eggshells, have been unearthed. The earliest of these, dating back about 39,000 years, are the oldest decorations found in North China to date. Some are pierced, others are incised with lines or shaped like fish.

"These items were not necessities for survival," Wang says. "They represent adornment, aesthetics and symbolic thinking."