Researchers have successfully extracted proteins from the enamel of six Homo erectus teeth discovered in China. A variant shared by Homo erectus and Denisovans raises the possibility that genetic heritage from this ancient human population was passed on, via Denisovans, to some humans living today in Asia and Oceania.
For most of the 20th century, it was customary to describe the Human evolution Like an orderly tree: a central trunk that branches out into separate branches, with each species of early man occupying its own defined place. According to the simple description, Homo sapiens evolved in Africa, spread around the world, and replaced the other human species it encountered.
Genetic discoveries over the past three decades have challenged this picture. It has become clear that modern humans outside Africa carry Neanderthal DNA, and that populations in Asia and Oceania also inherited genetic material from Neanderthals.DenisovansNow a study published in the journal Nature adds another intriguing possibility: it may also Homo erectus, an ancient human species that lived for nearly two million years, indirectly contributed to the genetic heritage of humans living today.
The study, led by Xiaomi Fu of the Chinese Academy of Sciences, was based not on DNA but on proteins preserved in the enamel of six teeth that are about 400 years old. The teeth were found at three sites in China: Juqudian, where fossils were discovered “Peking man”; Hexian; and Songjiadong. Five of the teeth belonged to males and one to a female.
When the DNA is gone, the proteins remain
Extracting DNA from ancient fossils is highly dependent on preservation conditions. Heat, humidity, bacterial activity, and chemical processes break down molecules over time. In East Asia, where the climate in many areas is hot and humid, the chances of finding DNA that is hundreds of thousands of years old are particularly low.
tooth enamel, on the other hand, is the hardest tissue in the body. The proteins involved in its formation may persist long after the DNA has completely broken down. Using mass spectrometry, researchers can identify the amino acid sequence in proteins and compare it to sequences from modern humans and ancient hominids.
The new study is an example of a field known as paleoProteomics – Research Ancient proteinsThe method does not provide complete genetic information like DNA sequencing, but it is able to identify tiny differences in protein sequences, and sometimes even determine the sex of the individual using different forms of the amelogenin protein encoded on the X and Y chromosomes.
The researchers extracted hundreds to thousands of protein fragments from each tooth. They focused, among other things, on ameloblastin, a protein that helps develop tooth enamel.
A molecular signature not found in any other population
All six teeth contained the same single amino acid change in the ameloblastin protein. The variant, designated AMBN(A253G), has not been found in Neanderthals, Denisovans, modern humans, Homo antessurus from Spain, or Homo erectus from Dmanisi, Georgia.
The fact that the same variant was found in teeth from three sites far apart in northern and southern China strengthens the possibility that this is a characteristic sign of Homo erectus populations that lived in East Asia during the Middle Pleistocene.
The find also helped resolve a controversy surrounding the Xian fossils. The structure of the fossils at this site is somewhat different from the “Peking Man” fossils, and some researchers have suggested that they may belong to Denisovans or another population. The shared protein signature suggests that the Xian teeth also belonged to Homo erectus.
A variant shared by Homo erectus and Denisovans
The bigger surprise came from another variant in the same protein, AMBN(M273V). It is also found in all six Homo erectus teeth, but unlike the first variant, it is also known from Denisovans.
The corresponding genetic variant is also found in modern humans, but its distribution is not uniform. According to the study, it is found at a frequency of about 21% in the Philippines, about 1.17% in India, and about 0.71% in Papua New Guinea, and is almost absent in most other populations tested. ([dui][1])
The researchers suggest that the variant did not originate in Denisovans. They may have acquired it from a population closely related to Homo erectus that lived in East Asia, following encounters and interbreeding between the two populations. The Denisovans then passed the variant on to some of the ancestors of modern humans in Asia and Oceania.
The process by which genetic material passes from one population to another through reproduction is called introgression, or genetic insertion. In this case, it is a possible chain of transmission: from Homo erectus to Denisovans, and from Denisovans to Homo sapiens.
The study does not prove that all humans carrying the variant today are direct descendants of the Homo erectus population studied. The proteins do not allow for a complete family tree to be reconstructed, and the variant may have also existed in other closely related populations. However, the combination of the ancient proteins, the Denisovan genome, and the distribution of the variant in modern humans provides support for a model of gene flow between ancient human populations in East Asia.
Intermixing between human species was not an unusual event.
The picture emerging from the study of human evolution is very different from the old story of separate species replacing each other. Almost every early human population from which researchers have been able to extract genetic information shows evidence of admixture with other populations.
Modern humans originating outside Africa carry, on average, a few percent of Neanderthal DNA. Papua New Guinea and some Australian and Southeast Asian populations also have significant Denisovan heritage. The genomes of populations in West Africa have been found to show signs of contact with an ancient human population whose identity is still unknown.
The Denisovans themselves were not a “pure” genetic population. Previous studies have suggested that they received genetic material from a very ancient population that split from the ancestors of Neanderthals, Denisovans, and modern humans more than a million years ago. Homo erectus has long been considered one of the candidates for the identity of that “super-archaic” population. The new study provides the first direct molecular clue to support this possibility.
A branched network instead of a tree
Homo erectus was one of the most successful human species. Fossils attributed to it have been found in Africa, West Asia, China, and Indonesia. The site at Dmanisi, Georgia, which is about 1.8 million years old, is considered the earliest accepted evidence of the presence of members of the genus Homo outside Africa.
In China, Homo erectus existed for more than a million years, and on the island of Java, populations may have survived until about 100 years ago. The long duration of existence and the wide geographical distribution increased the chance of encounters with other human populations.
So it might be better to describe human evolution not as a tree with separate branches, but as a river that branches into channels that come together and then separate. Populations evolved separately for long periods, but when they met they could reproduce and exchange genetic material.
The distinction between one “species” and another remains useful for sorting fossils and describing anatomical differences, but the biological boundaries between ancient human populations were more permeable than previously thought.
What else is hidden in tooth enamel?
The method’s potential goes beyond Homo erectus. Fossils of other human populations have been found in East and Southeast Asia that have not yet yielded DNA. These include Homo floresiensis, nicknamed “the hobbit” and living on the island of Flores in Indonesia, and Homo lozonensis from the Philippines.
It is not known whether these populations disappeared completely or passed on some of their biological heritage to succeeding populations. If it becomes possible to extract proteins from their tooth enamel, it may be possible to examine their relationship to other human species and look for evidence of encounters and genetic transfer.
The protein shared by Homo erectus and Denisovans does not yet reveal whether it had a special biological function. Other Denisovan variants that have survived in modern humans are associated with, among other things, the immune system and adaptation to high altitudes. However, in this case, it is not yet known whether the change in the ameloblastin protein affected tooth structure or conferred any advantage.
The important finding at this stage is the very existence of the molecular connection. A population that was considered for years to be an evolutionary branch that went extinct without leaving a trace may be part of the genetic mosaic from which later human populations were built.
Source and original article
Qiaomei Fu, Zhongyou Wu, E. Andrew Bennett et al., “Enamel proteins from six Homo erectus specimens across China,” Nature, vol. 655, pp. 141–147, published May 13, 2026. DOI: 10.1038/s41586-026-10478-8.
Questions and Answers
How can biological information be extracted from a fossil that does not contain DNA? Tooth enamel proteins are more durable than DNA and can survive for hundreds of thousands of years or even longer. Amino acid sequence analysis makes it possible to identify differences between ancient human populations and species.
Does the study prove that Homo erectus is a direct ancestor of humans living today? No. The study suggests that genetic material from a population related to Homo erectus may have passed to Denisovans, and from them to some modern humans. This conclusion is based on a shared protein variant, not on the full Homo erectus genome.
Who are the Denisovans? The Denisovans were an early human population closely related to Neanderthals. They are known primarily from fossils and DNA found in Denisova Cave in Siberia, but additional evidence suggests they were widespread in East Asia.
In which modern populations is the shared variant found? According to the study, the corresponding genetic variant is found to be particularly prevalent in the Philippines, and to a lesser extent in India and Papua New Guinea. The researchers believe it reached these populations through Denisovan heritage.
Why is the discovery important for understanding human evolution? It reinforces the understanding that human evolution was not a simple sequence in which one species replaced another. Different populations met, interbred, and passed genetic material between them over hundreds of thousands of years.
For the scientific article: Opening the scientific article
More on the subject on the science website
- The evolution of human body size was not a straight path of growth.
- A skull found in Kenya heats up the debate about Homo erectus
- How Homo erectus survived in harsh desert conditions over a million years ago
- The toolbox of prehistoric man
- The Turkana Rift in Africa, the cradle of humanity, ruptured faster than thought
One response
It is unclear whether protein in tooth enamel indicates genetic mixing or cannibalism.