https://en.people.cn/n3/2026/0514/c90000-20456062.html

https://www.nature.com/articles/s41586-026-10478-8

Proteins extracted from six teeth of early humans residing in what is now China around 400,000 years ago provide new insights into how ancient genetic material may have made its way into modern humans.

An analysis of the tooth proteins from Homo erectus, the first human ancestor to walk out of Africa, was reported this week in the journal Nature. It identifies a genetic marker also found in Denisovans, a little-known early human group first found in a Siberian cave, and in some modern human populations today, suggesting the two ancient populations may have coexisted and interacted in parts of East Asia.

Until now, the genetic research on the Homo erectus has been limited because ancient fossils are too precious, and traditional sampling methods require grinding or drilling into the teeth. As a result, compared with other known human species, their genetic characteristics, population diversity, and especially their potential links to modern humans remain unresolved.

A Chinese research team overcame that barrier using a micro-destructive acid etching technique that removes only a tiny superficial layer of tooth enamel without visibly damaging the fossil. This technique, developed in 2011, was first used for sex determination of ancient human teeth from less than 10,000 years ago and subsequently adapted for the examination of other animal teeth.

From six ancient human teeth uncovered from three sites in China, including Zhoukoudian, where the Peking Man fossils were discovered, researchers extracted enamel proteins dating back at least 400,000 years. These are the oldest ancient human proteins ever obtained in East Asia, pushing the molecular record back from roughly 160,000 years to at least 400,000 years, the study said.

The researchers identified two key mutations in the tooth proteins. One, called AMBN-A253G, was found in all six fossil teeth but has never been seen in other human species, modern humans or apes. That makes it a unique molecular marker for this East Asian population and proves that the physically diverse fossils from the three Chinese sites all belonged to the same genetic group. The second mutation, AMBN-M273V, had previously been thought to be specific to Denisovans. But the study found the same mutation in the much older 400,000-year-old teeth, indicating that it is shared by Homo erectus.

This suggests the mutation may have originated in the older East Asian population and then flowed into Denisovan groups through interbreeding. From Denisovans, it was passed into the ancestors of some modern humans, particularly in Southeast Asia and Oceania, after a second wave of interbreeding, a process scientists named “introgression.”

The findings reveal a previously unknown aspect of human evolution: the East Asian Homo erectus was not only a distinct evolutionary lineage but also one of the sources of ancient genes in the modern human gene pool.