\n Proteins, which are made up of sequences of amino acids, are more robust than ancient DNA, a fragile molecule that degrades relatively easily. Proteins contain far less detailed information, but they can still shed some light on a specimen\u2019s evolutionary history.\n <\/p>\n
\n Fu, a professor at the Institute of Vertebrate Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences in Beijing, and her team used what they described as a new, less invasive technique to study fossils without damaging their morphology.\n <\/p>\n
\n Rather than drilling, they used acid etching to remove a small sample of enamel from the teeth. The team did not try to recover DNA from the fossils after failing to extract DNA from animal fossils of the same age from the same sites. Fu said it was hard to get DNA, but she would never give up.\n <\/p>\n
![\"Two](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/05\/1778835620_779_site.jpg\")
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\n The researchers found that the specimens from the three sites in China shared two amino acid variants, one of which was previously unknown. This finding, the researchers reasoned, suggested the teeth all belonged to the same species.\n <\/p>\n
\n The second variant had previously been identified in Denisovans, another shadowy species of ancient human<\/a>, and also in some modern human populations.\n <\/p>\n \n That other human species shared this variant suggested that Denisovans had once interbred with Homo erectus, and then, at some later point, Denisovans mated with Homo sapiens, according to the study.\n <\/p>\n \n As a result, traces of Denisovan DNA live on in some humans today \u2014 something interbreeding geneticists call admixture.\n <\/p>\n \n Similarly, modern human populations have some Neanderthal ancestry \u2014 a legacy of past interactions with that species that went extinct about 40,000 years ago. Denisovans also interbred with Neanderthals.<\/a>\n <\/p>\n \n Modern human populations in Southeast Asia have the highest Denisovan ancestry<\/a>, suggesting the two groups once crossed paths there.\n <\/p>\n \n Geneticists knew that Denisovans had some ancestry from an unknown \u201cghost lineage\u201d with no DNA match, and Homo erectus was one possible candidate, said Eduard Pop, a research scientist at Naturalis Biodiversity Center in Leiden, Netherlands, via email.\n <\/p>\n \n \u201cThis study strengthens that link,\u201d said Pop, who is working with researchers to understand if protein information is preserved in Homo erectus fossils found in Indonesia.\n <\/p>\n \n \u201cIt suggests that East Asian Homo erectus-related populations may have contributed genetically to Denisovans, and through them indirectly to some modern humans,\u201d he said.\n <\/p>\n \n \u201cSo it fits with a view of human evolution in Asia as a network of populations that sometimes overlapped and interbred, rather than a set of clean, isolated branches.\u201d\n <\/p>\n \n From the protein information, the researchers were also able to determine the sex of the fossils \u2014 five males and one female \u2014 by identifying a sex-specific marker in a tooth enamel gene on the Y chromosome.\n <\/p>\n \n Work published in 2020<\/a> retrieved proteins from an early Homo erectus fossil found in Dmanisi, Georgia, but, unlike the new study, Pop noted it didn\u2019t reveal any detailed information about how the species sits in relation to other hominins.\n <\/p>\n \n The fossils came from three sites in central and northern China: Zhoukoudian, Hexian and Sunjiadong. The country has a long history of the discovery of Homo erectus fossils. In the 1920s and 1930s, hundreds of fossils were excavated from Zhoukoudian,<\/a> including several skulls. The remains became known as Peking Man. However, the fossils, packed in two wooden crates, went missing during the chaos of World War II.\n <\/p>\n \n The tooth from Zhoukoudian used in this latest research was discovered during an excavation from 1949 to 1951, the study noted.\n <\/p>\n \n Homo erectus was the earliest human species to have body proportions similar to those of Homo sapiens. They had an upright stance, a large face with a protruding brow and no chin. Fossil evidence for Homo erectus stretches over more than 1.5 million years, far longer than the 400,000 years that Homo sapiens have been around, making the former species by far the longest surviving of all human relatives, according to London\u2019s Natural History Museum<\/a>.\n <\/p>\n \n The new study relied heavily on the hypothesis that Denisovans and Homo erectus interbred, but the Smithsonian\u2019s McRae said an alternative explanation could be possible given that the Homo erectus fossils were 400,000 years old and the oldest known Denisovan fossil included in the study is the Dragon Man cranium, which is 150,000 to 300,000 years old.\n <\/p>\n \n \u201cEven at the closest, there is still a 100,000 year gap between the two species, meaning that an ancestor-descendant relationship could be an alternative possibility,\u201d he said via email, suggesting that Denisovans perhaps evolved directly from Homo erectus rather than coexisting.\n <\/p>\n \n \u201cTransmission of the amino acid variant through interbreeding is certainly possible, I would even say plausible, but archaeological evidence could help confirm a closer connection between the two groups,\u201d he added.\n <\/p>\n \n Fu agreed the information her team gleaned from tooth enamel was not detailed enough to understand how Homo erectus is related to other humans. Only DNA would really provide that granular information, she said. Fu described the study\u2019s finding as a \u201cstone thrown in a pool with a big splash,\u201d opening up new questions for future research.\n <\/p>\n![\"Another](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/05\/1778835621_464_tooth-1.jpg\")
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