July 08, 2014

Neandertal-like temporal labyrinth of Xujiayao 15

From the press release:
While it's tempting to use the finding of a Neandertal-shaped labyrinth in an otherwise distinctly "non-Neandertal" sample as evidence of population contact (gene flow) between central and western Eurasian Neandertals and eastern archaic humans in China, Trinkaus and colleagues argue that broader implications of the Xujiayao discovery remain unclear.  
"The study of human evolution has always been messy, and these findings just make it all the messier," Trinkaus said. "It shows that human populations in the real world don't act in nice simple patterns.  
"Eastern Asia and Western Europe are a long way apart, and these migration patterns took thousands of years to play out," he said. "This study shows that you can't rely on one anatomical feature or one piece of DNA as the basis for sweeping assumptions about the migrations of hominid species from one place to another."
I think this study highlights the possibility that some of the traits thought to be characteristic of Neandertals may in fact be part of Eurasian hominins in general, and the fact that they have been associated with Neandertals is a consequence of the much greater attention paid to that species until recently. As East Eurasian Pleistocene Homo becomes better described, it may become clear what are indeed the traits that were specific to H. neanderthalensis.

PNAS doi: 10.1073/pnas.1410735111

Temporal labyrinths of eastern Eurasian Pleistocene humans

Xiu-Jie Wu et al.

One of the morphological features that has been identified as uniquely derived for the western Eurasian Neandertals concerns the relative sizes and positions of their semicircular canals. In particular, they exhibit a relatively small anterior canal, a relatively larger lateral one, and a more inferior position of the posterior one relative to the lateral one. These discussions have not included full paleontological data on eastern Eurasian Pleistocene human temporal labyrinths, which have the potential to provide a broader context for assessing Pleistocene Homo trait polarities. We present the temporal labyrinths of four eastern Eurasian Pleistocene Homo, one each of Early (Lantian 1), Middle (Hexian 1), and Late (Xujiayao 15) Pleistocene archaic humans and one early modern human (Liujiang 1). The labyrinths of the two earlier specimens and the most recent one conform to the proportions seen among western early and recent modern humans, reinforcing the modern human pattern as generally ancestral for the genus Homo. The labyrinth of Xujiayao 15 is in the middle of the Neandertal variation and separate from the other samples. This eastern Eurasian labyrinthine dichotomy occurs in the context of none of the distinctive Neandertal external temporal or other cranial features. As such, it raises questions regarding possible cranial and postcranial morphological correlates of Homo labyrinthine variation, the use of individual “Neandertal” features for documenting population affinities, and the nature of late archaic human variation across Eurasia.

Link

5 comments:

Lisa Evans said...

Any reason not to think that some of these East Eurasian Pleistocene Homo samples are from Denisovans? Maybe they looked a lot more like modern humans than Neanderthals did.

Mehedi Hasan Mamun said...

And yes I think labyrinth have some variation and separate from the others.

Rokus said...

While it's tempting to use the finding of a Neandertal-shaped labyrinth in an otherwise distinctly "non-Neandertal" sample as evidence of population contact (gene flow) between central and western Eurasian Neandertals and eastern archaic humans in China, Trinkaus and colleagues argue that broader implications of the Xujiayao discovery remain unclear.

Indeed, and the article doesn't clarify any other implication but Neanderthal contact either. Wu's efforts to downplay the possibility of Neanderthal influence by stating that the occurence of this Neanderthal feature of temporal labyrinths in Xujiayao (XJY) 15 implies this trait "to become less Neanderthal" because now it seems that "many of the purported “Neandertal” features were widespread during the Pleistocene" is rather circular to gene flow. This fossil is 123 ka at most, while the Neanderthal package of archaic features is much older than that.
Instead, the broader implications may just be that Neanderthal reached eastern Asia quite early and mixed with local archaics. Neanderthal influences on east Asian archaics ("Continuity with Hybridization" according to Wu et al., 2004) had already been suspected earlier and I truly wonder why this wasn't cited in this article.

42ee6ae6-0d53-11e4-8137-2b4cbe0f7e71 said...

Would be interesting to see what Haplogroup this Xujiayao 15 belongs to.

42ee6ae6-0d53-11e4-8137-2b4cbe0f7e71 said...

Wonder what genetic Haplogroup Xujiayao 15 was from?