Patterns of human evolution in northeast Asia with a particular focus on Salkhit

Despite the well published mixture of archaic and modern features in fossil hominins, a presence of archaic features is still used as a basis for a claim of an archaic specimen. In this paper, the archaic appearance of a hominin fossil specimen from Salkhit, Mongolia, is examined to ask if Salkhit looks archaic because it is an archaic specimen like a classic Homo erectus. The morphology and metrics of the Salkhit skullcap was compared with Middle and Late Pleistocene hominin fossils from Zhoukoudian: Locality 1 and Upper Cave. Results show that the archaic features that Salkhit shares with the Locality 1 sample are also shared with the other sample, Upper Cave. On the basis of metrics, Salkhit is intermediate between the Locality 1 and the Upper Cave specimens. Salkhit is different from the Middle Pleistocene materials in the same way later hominins differ from the Middle Pleistocene sample, in having a broader frontal and thinner supraorbital region. This may reflect encephalization and gracilization, a modernization trend found in many places. Results of this paper are not compatible with the null hypothesis that Salkhit is like a member of the Zhoukoudian H. erectus sample. Archaic features may have different explanations: they can be diagnostic features of an archaic species, or regionally predominant features. It is concluded that the latter explains the archaic features of Salkhit.