Scientists at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences have uncovered molecular evidence that could point to a previously unknown connection between Homo erectus and modern humans. At the same time, the team developed new paleoproteomics techniques that can extract valuable information from fossils while causing very little damage. Homo erectus, or H.erectus, occupies an important place in human evolutionary history because it was the first species in the genus Homo known to have migrated out of Africa.
Yet scientists still know relatively little about its genetic makeup, the diversity of its populations, or how it may have been related to later human groups. One major reason is the shortage of molecular evidence from H. erectus. Without DNA or other preserved biological molecules, researchers have struggled to determine whether these ancient humans contributed genetically to populations that came later.
This uncertainty has made the evolutionary role of H. erectus one of the enduring questions in the study of human origins. Extracting Molecular Clues Without Ruining Fossils Studying molecules preserved in H. erectus fossils presents another challenge. Ancient human remains are both scientifically irreplaceable and culturally important, making sampling methods that significantly damage fossils unacceptable in many cases.
That limitation has slowed attempts to obtain molecular information from these specimens. A research group led by FU Qiaomei of IVPP, working with scientists from several institutions, has now found a way around much of that problem. The team used an acid etching technique that requires only very small amounts of material to recover molecular information from six Homo erectus teeth while leaving the shape of the fossils intact.
The findings were published online in Nature. A commentary published at the same time in Nature emphasized the importance of enamel proteins recovered from the six Chinese H. erectus teeth, saying they provide "new insights into how ancient genetic material was eventually introduced into modern human populations." 400,000-Year-Old Teeth Reveal Two Key Mutations The researchers detected two mutations in teeth from three Chinese fossil sites: Zhoukoudian (Peking Man), Hexian, and Sunjiadong. The fossils date to at least 400,000 years ago, and the molecular evidence points to possible genetic connections between East Asian H. erectus and Denisovans.
Denisovans, in turn, are known to have contributed genetic material to some modern human populations. One of the mutations, AMBN A253G, had not previously been identified. The researchers propose that it could serve as a molecular marker for these H. erectus populations.
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