進化：ラオスで見つかった更新世中期のヒト族の臼歯

A molar, from a middle Pleistocene hominin specimen, that was found in the Tam Ngu Hao 2 cave in Laos is described in a Nature Communications paper. The tooth may have belonged to a young, female Denisovan and could aid our understanding of the population history of Southeast Asia.

The presence of hominins in continental Southeast Asia is primarily understood from limited stone tool records and sparse human remains. It is unknown if one or more human lineages existed or co-existed in southern Asia. Genetic analysis has suggested that some Southeast Asian populations retain a Denisovan ancestry, but the geographic range of Denisovans remains debated.

Fabrice Demeter, Clément Zanolli, Laura Shackelford and colleagues describe a molar found in the limestone cave Tam Ngu Hao 2 (Cobra Cave) in the Annamite Mountains of Laos. The cave also included the fossilized remains of animals, such as rhinoceros, tapirs, and sambar deer. The authors used a series of dating methods and estimate that the sediment surrounding the tooth is between 164–131 thousand years old. The authors indicate that the molar is unworn and had only recently completed development. They suggest that the individual was between 3.5–8.5 years of age at death. They analysed proteins in the tooth alongside its morphology and suggest that it is from the genus Homo and they further indicate that the individual was female. They compared the internal and external morphology of this molar to other hominins, including Neanderthals, recent humans, and Homo erectus, using geometric morphometrics (three-dimensional shape statistics), and suggest it to be most likely Denisovan.

While the authors cannot exclude the molar belonging to a Neanderthal, they suggest that its similarity to a Denisovan specimen from Xiahe, China supports their findings. The molar expands our understanding of hominin dispersals through Asia and demonstrates this region was a hotspot for the genus Homo, they conclude.