|All in a row...Regourdou 1's lower front tooth crowns viewed labially.|
In this case, it's the breath-taking intellectual journey of Volpato et al. from scratches on the anterior mandibular teeth of the Regourdou 1 Neanderthal to language ability comparable to that of modern humans. Thanks to Bob Muir for his good natured challenged to me to say something about the latest plonk from PLOSONE. So, I read it. And here is my response.
O. M. G.! Sorry. Disdain attack. I'll be fine in a minute.
Boiled down, the authors are ostensibly presenting novel evidence for handedness among the Neanderthals, in the form of scratches on dental enamel. That's it! That's all there is. Possibly useful information. But even their foundational inference is open to question, because it's based on an unwarranted assumption. As a result, the follow-on inferences lose cogency, one misstep at a time. A good number of inferential leaps occur in this paper. I'll enumerate them here.
Leap number one. Volpato et al. examined the labial surfaces of the six lower anterior teeth of an adult Neanderthal. They found scratches that they attribute to accidental contact with a sharp stone [presumed to be an artifact]. But only those scratches on the incisors count as artifact-induced damage--those occurring on the canines must, according to the authors, be environmental, rather than of cultural or behavioral origin, since they are shorter and less frequent. [I would guess that this could easily be due to the canines' location deeper in the mouth and the possibility that whatever is scratching the teeth during life was positioned more toward the front of the mouth.]
Leap number two. The preponderance of the surface scratches, when viewed from the front, are oriented with left end lower than the right. With no explanation, the authors [again] presume that the course of the sharp object must have been from left to right from the Neanderthal's point of view--in other words, from upper left to lower right--rather than the other way around.
Leap number three. Based on the assumption that the scratches were made by a stone tool or tools, and the further assumption that they show a preferred oritentation, and that therefore this stands as evidence of the Neanderthal's preference for using the right hand to wield the sharp object, the authors conclude that the scratches must have occurred while the Neanderthal was in the act of cutting off a hunk of [presumably] meat after stuffing a morsel in the oral cavity. For this, they simply cite C.L. Brace's characterization of a documented modern human practice as the 'stuff and cut' technique, and paste it onto their narrative about a Middle Pleistocene hominid. [Why the Neanderthal didn't just bite off a chunk, as you or I would, the authors don't explain. I guess they were trying to be genteel in a ravenous, trogolodytic sort of way.]
Leap number five. Again by analogy to modern humans, the brain lateralization inferred by the authors is tied to the notion that brain lateralization in us is predominantly due to the brains preference to house the language capacity in the opposite side of the brain from the right hand. [Again, I'm afraid this raises the question 'What about left-handed people?']
|Kebara 2 hyoid|
Leap number seven. Taken together, all six of the above leaps converge on the conclusion that Neanderthals had linguistic capabilities. Quite an intellectual journey! No?
homology, and it is a pillar of evolutionary theory. It's simply wrong to view any structure that's visible in the fossil record and formally similar to that occurring in modern humans as evidence that similar somatic or neurological functions or behaviours were present in the fossil form. This goes for brain morphology as much as it does for biomechanics or any other facet of past life that can be observed in the skeleton. It's why I cannot view the emergence of the modern skeleton at almost 200 kya as evidence that modern humanity arose at the same time.
In the illustration of homology up above, it's plain to see that the front limbs of vertebrates have evolved for very different purposes, even though the skeletal elements themselves are the same--i.e. they have the same embryological origin, and thus they all express the same skeletal elements. Even within these groups there is considerable inter-specific variation in these structures. This is why I'm very wary when similar structures in the hominid past are unequivocally treated as having the same function as they do in modern humans.
Thanks for dropping by! If you like what you see, follow me on Twitter, or friend me on Facebook. You can also subscribe to receive new posts by email or RSS [scroll to the top and look on the left]. I get a small commission for anything you purchase from Amazon.com if you go there using any link on this site. There's a donate button, too. Your generous gift will always be used to augment the site and its contents.