Neanderthal and Human Brain Growth

I was hoping to have a more in depth post on this for the upcoming edition of the Four Stone Hearth but I am not going to get it finished in time. Here is the short version.

There is an interesting paper on brain growth in Neanderthals and modern humans in Current Biology. The paper follows up on this paper. In the current Biology paper Gunz et al argue that:

The difference between the developmental patterns of modern humans and Neanderthals is most prominent directly after birth, when the shape of the vault is extremely sensitive to the tempo and mode of brain growth … When the cranial bones are thin and not yet fully ossified, the shape changes of the frontal and parietal bone are largely driven by the increase in brain volume. While the growth of the face affects the shape of the cranial base …, it is unlikely that this alone could explain the shape changes of the parietal and occipital bone shown in Figure 1. We suggest, therefore, that species differences in brain growth rates … and timing underlie the uniquely modern human globularization phase.

During dental ages 2-6, according to Gunz et al endocranial shape changes are similar in chimps, humans, and Neanderthals. In the PNAS paper (linked to above) it was argued that two distinct developmental trajectories are identified with the modern human trajectory being more derived than the Neanderthal and the Current Biology paper links this, briefly, to Green et al paper “A draft sequence of the Neandertal genome.” – which identified some genes having to do with cognition that are derived in modern humans.

At some point I will have more to say on this. In the meantime, check out the Current Biology paper. Also, if you haven’t already please submit any interesting anthropology posts you come across to either myself or Duane at Abnormal Interests.

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2 Responses

  1. Thank you for the link to the original article- I had only seen the various coverage of this story in the popular science webpages, and posted in my own blog about the various titles the media chose to give to this topic!

  2. Quoting Stan Freberg: “grumble grumble grumble mutiny mutiny mutiny…”

    I see the point they want to make. But.

    1. It’s generally accepted that Neandertals were heavier — on average — than contemporary anat mod Homo sapiens sapiens(bigger bones, bigger muscles, different muscle-tendon-bone linkages, etc). This seems to imply bigger brains. I dunno how much bigger; I’m sure there are papers floating about dealing with encephalization in late hominids. Bigger brains = bigger heads.

    2. It’s generally accepted that Neandertals were shorter and more stoutly built than anat mod Homo sap saps, but not to any obnoxious esthetic extent. Crudely put, pelvuses and birth canals for female Neandertals were not exceptionally sized when compared to contemporary Hss. My guess is they were about the same, give or take a standard deviation — again, there’s probably a paper or two on this floating about.

    Larger neonatal heads shoved through same-size pelvuses would possibly pose increased risks to both Neandertal babies and mothers, compared to Hss, if Neandertal and Hss infants had heads of the same shape. If Neandertal infant heads were say longer in length but about the same width as Hss counterparts — a notion which we generally accept for adults — the dangers of childbirth might be reduced.

    Yes, I’m handwaving. The point is, different shaped heads might have a different explanation than different development maturation of brains. There are long-skulled and broad-skulled individuals and even populations so characterized in the modern world — should we proclaim this as “species difference” as well?

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