American scientists analyzed the genome of an ancient human from the Maludong (Deer Cave) cave in China, which was published in 2022 and who lived approximately 14,000 years ago. They concluded that the initial, widely publicized study's conclusions were flawed, and that the sample itself was likely heavily contaminated with modern human DNA. Critical comments on the article were published in the journal Current Biology, and the scientists posted supplementary material as a preprint on bioRxiv.org.
In 1989, in Maludong Cave (Deer Cave) in southern China, researchers discovered ancient human remains: a braincase, several other skull and jaw fragments, a pair of teeth, and fragments of a femur and tibia. Although the remains belonged to people who lived at the end of the Pleistocene—approximately 14,000 years ago—they displayed a combination of features common to both sapiens and more archaic members of our genus. Analysis of these bones and finds from another Chinese cave, Longlin, led some scientists to hypothesize that this mosaic morphology may be the result of hybridization between different species.
In 2022, Chinese scientists presented the results of a genetic study of the remains from the Maludong site. They reported isolating ancient DNA from a fragment of the cranial region of the MLDG-1704 skull. The analyzed sequence, code-named MZR, represented the first genome sequence of a late Pleistocene human from southern East Asia. The scientists determined that the remains belonged to a sapiens woman with no evidence of recent admixture with archaic populations. Furthermore, one of the key findings of this study was that the population to which the Maludong individual belonged is genetically very similar to a significant portion of Native American ancestry.
However, American paleogeneticists and bioinformaticians, led by renowned researcher David Reich of Harvard University, submitted critical comments on this article to the journal Current Biology, where the Maludun genome was published almost three years ago. The American scientists' arguments effectively negate all previous findings from genomic analysis. According to the authors, the DNA sequence does not meet the criteria for use in population studies.
Critics noted the very high number of errors in the published sequence, with the level of errors being extremely high even for mitochondrial DNA, the coverage of which is typically orders of magnitude higher than that of nuclear DNA. For example, American scientists noted that the error rate in the mitochondrial DNA sequence was so high that they were unable to even determine which mitochondrial haplogroup the individual carried, let alone draw more detailed conclusions about the individual's maternal lineage, as contained in the original work.
The American researchers also posted some of their critical comments and reflections on this genome as a preprint on bioRxiv.org. Their gist is that the sample selected for analysis was apparently heavily contaminated with modern genetic material. Moreover, approximately 90 percent of the published DNA sequence can be modeled on the DNA of a modern resident of China, the location where the original research was conducted. However, the Americans were unable to isolate exclusively fragments of the ancient DNA sequence from this genome.
Anthropological finds from China often spark debate. We discussed one such story, related to the question of when the first sapiens settled in what is now China, in our article "Teeth of Discord."
