Another species? or maybe a Denisovan? A paper (The Innovation, DOI: 10.1016/j.xinn.2021.100130 and DOI: 10.1016/j.xinn.2021.100132, Massive cranium from Harbin in northeastern China establishes a new Middle Pleistocene human lineage) published today, describes a crania discovered in 1933 in Harbin, northern China, but only re-discovered a few years ago, and studied now.
The paper cautiously suggests in a covert manner that this Harbin skull may be a Denisovan one:
"The sister relationship between Harbin and Xiahe, as identified by Bayesian inference (but not parsimony analysis, see the supplemental information), is particularly interesting. The Xiahe mandible shows some proteomic features of the Denisovans, who were informally called “Homo sapiens altaiensis” or “Homo altaiensis,” and sediments from Baishiya Cave have yielded Denisovan mtDNA. The Harbin M2 also matches the known permanent Denisovan molars in size and root morphology, and, ever since the discovery of Denisovans, Asian Middle Pleistocene hominins, such as Dali, Jinniushan, and Xujiayao, have been suspected to represent an East Asian population of the Denisovans"
The remains have been dated to "a minimum age ... of ∼146 ka"
Regarding divergence from the Homo sapiens line, it has some interesting findings: (bold font is mine)
"The results of the Bayesian tip-dating analyses suggest that the Harbin and Xiahe fossils shared a common ancestor ∼188 ka (397–155 ka), and the clade, including the Harbin cranium and H. sapiens shared a common ancestor at ∼949 ka (1,041.41–875.25 ka). The Neanderthal-H. sapiens divergence time in our analysis was ∼1,007 ka (1,114–919 ka). This estimation falls in the range based on mtDNAs for the split between the basal Neanderthal (Sima de los Huesos) and the H. sapiens lineage, but is much older than the estimation based on nuclear DNAs for the splits between the Neanderthal and H. sapiens lineages. However, it is possible that this younger estimated divergence date is an artifact of statistical averaging between “super-archaic” and “recent gene flow” events. The common ancestor of the H. sapiens OTUs (NOTE: OTU is an "Operational Taxonomic Unit", and the term means that the beings under study share a given set of observed characters). included in our analysis is as old as ∼770 ka (922–622 ka), suggesting that the H. sapiens clade has a much deeper origin time than previously estimated.
The Eurasian H. sapiens OTUs share a common ancestor ∼416 ka (534–305 ka) old. Outside of Africa, however, the earliest known H. sapiens fossil is only ∼210 ka.
There is a large time gap between the hypothetical common ancestor of Eurasian H. sapiens and the actual fossil record, from the Bayesian tip-dating analysis. One plausible hypothesis is that the ancestral population of Eurasian H. sapiens may have diversified in Africa for many millennia before they dispersed into Eurasia. Genetic studies on ancient DNA suggest that the initial genetic exchanges between Neanderthals and H. sapiens occurred between 468 and 219 ka, or between ∼370 and 100 ka, and the introgression may have originated through gene flow from an African source. Interestingly, not only does the estimated time of the introgression event between Neanderthals and H. sapiens roughly overlap our prediction for the age of the common ancestor of Eurasian H. sapiens, but the African origin of the introgression is also consistent with our African ancestral population hypothesis.
(...)
Africa is the major source of Homo dispersals. In total, ∼40% of all the dispersals are from Africa, while Africa also receives ∼22% dispersals from Asia and Europe. Instead of a unidirectional “out of Africa” model, a multi-directional “shuttle dispersal model” is more likely to explain the complex phylogenetic connections among African and Eurasian Homo species/populations."
Let's hope that DNA can be extracted from the skull, it could confirm that this man was in fact a Denisovan.
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Very interesting post!… Whether Harbin could be further identified as a Denisovan (an amazing possibility) or he was simply another species, the authors are clearly proposing that he belongs to a monophyletic clade (that is; a one that includes the last common ancestor and all its descendents), that is a sister one of H. sapiens clade.
ReplyDeleteWhat calls my attention is that this new clade not only includes other species as Xiahe, Dali, Jinniushan and Hualongdong, but apparently European H. antecessor too…!! (as shows Fig. 4 of this paper).
At this last respect, and taking into account that H. antecessor (ca. 800ka) would be much more closely related to modern humans than previously supposed (from your post on April 5, 2020), I am tempted to rise a schematic and risky speculation (which would be rather an open question);…in the hopefully case in which valid DNA can be successfully extracted from Harbin cranium… ¿Could an eventual “positive result” as a definite Denisovan individual, be enough to suggest that; as well these Far Eastern species could have constituted the Asian branch of the Denisova clade, H. antecessor could perhaps have been part of an ancient, remote and isolated European one..???
At least, it would be consistent with what the authors are holding ; …” these Homo lineages probably had a strong capability of dispersing for long distances, but remained in small and isolated populations”…
Best regards
Marcelo