June 21, 2014

Atapuerca skulls show "intermediate" features

H. heidelbergensis from Atapuerca
Cranium 5 "Miguelón"
(CC by José Manuel Benito)
This has been in the news all around this week with various emphasis, but probably the most important highlight is that, according to Atapuerca researchers, Homo heidelbergensis may well be a diffuse category with varied degrees of affinity to their Neanderthal successors.

J.L. Arsuaga et al., Neandertal roots: Cranial and chronological evidence from Sima de los Huesos. Science 2014. Pay per viewLINK [doi:10.1126/science.1253958]

Months ago, it was found that Atapuerca's H. heidelbergensis and the Denisova hominins formed a single mitochondrial DNA clade to the exclusion of Neanderthals and us. However Arsuaga et al. find that facial traits in the hominins of Sima de los Huesos seem to be already much closer to those of Neanderthals than to the local precursors. Instead other cranial traits such as brain size do not seem to change yet. 

There seems to be some uncertain speculation by the researchers on what this partial "neanderthalization" process in Atapuerca hominins could signify. 
"We think based on the morphology that the Sima people were part of the Neanderthal clade," Arsuaga said, "although not necessarily direct ancestors to the classic Neanderthals."

This, I guess, could indicate some sort of convergent evolution or be caused by some Neanderthal admixture on the male side.
Another important finding is that, contrasting with the similitude of the various specimens from Sima de los Huesos ("Chasm of the Bones", a key subsite of Atapuerca), other contemporary European specimens look quite different, suggesting that H. heidelbergensis was a quite diverse human species.

The study includes seven new specimens, as well as ten other previously reported ones.

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