As I understand it, their central message--that Neanderthals could talk--is motivated by what I and others consider some rather shaky suppositions, even though their scholarship and expertise in evolutionary psychology and archaeology are not in question. The first of their suppositions with which I take exception has to do with Broca's area--a lobe of the brain that's widely believed to be involved in our linguistic ability. Neanderthals and modern humans both exhibit a similar expansion of this part of the brain. That leads Tom and Fred to conclude that Neanderthals possess the same neurological substrate for language as that of modern humans.
The second supposition with which I take issue is based on the empirical observation that we and the Neanderthals both possess the human FOXP2 gene, which is reputed to be the genetic mechanism for our ability to carry on a conversation like the one I'm having with you right now. The third aspect of their evidence with which I have problems is the idea that the Levallois technique is evidence of a high degree of forethought and skill, which would imply a great deal of cognitive flexibility and scope for intelligent thought. I'll take each in turn.
Broca's Area: It's always possible that I missed something in my study of evolutionary theory, but I was under the impression that if two demes of a widely distributed population share a heritable trait, it's almost certain that the ancestral population also possessed that trait. The same would be true for different species in the same genus, and so on up the Linnaean hierarchy. If I'm correct in this assessment, all that can be said of Broca's area in relation to Neanderthals and modern humans is that we share a common ancestor who also exhibited the same degree of expansion in that area of the brain.
Moreover, while I have no disagreement with the idea that Broca's area is, in modern humans, one seat of language, my understanding of homology is that there's no reason to suspect that Broca's area expanded initially so that it could, one bright, evolutionary day, become that seat of language. In other words, the expansion of Brocas' area, which we must assume was present in the last common ancestor of Neanderthals and modern humans, need not have occurred in response to, nor as an adaptation that had anything to do with language. Like the swim bladder of the fishes, which has the same embryological origins as the lungs in humans, Broca's area must have become prominent for reasons other than to prepare for the day that human speech would need that part of the brain for its expression.
The FOXP2 Gene: The human FOXP2 gene, which we share with the Neanderthals, must also have been carried by the last common ancestor. Like Broca's area, the FOXP2 gene probably didn't arise, sui generis, as the trigger mechanism for whatever it is that allows me to say these things in a way that you're able to understand. Moreover, as I understand it, the human FOXP2 gene is inferred by some to be the fount of language because of observations of present-day modern humans who lack at least one faithful copy of the gene, and who are severely hampered in their ability to speak. Unfortunately for Fred, Tom, and those who'd like to infer from this that the FOXP2 gene is the key to our linguistic ability, in affected individuals, the effect of expressing an unfaithful copy of the gene results in
...severe impairment in the selection and sequencing of fine orofacial movements, which are necessary for articulation (referred to as a developmental verbal dyspraxia; MIM 602081). The disorder is also characterized by deficits in several facets of language processing (such as the ability to break up words into their constituent phonemes) and grammatical skills (including production and comprehension of word inflections and syntactical structure) (Lai et al. 2001) [emphasis added].The FOXP2 gene thus has a critical role in some of the abilities necessary for language production in modern humans. However, it's broader neurological reach means that it cannot be viewed as the genetic mechanism that makes us linguistic. Rather, the gene's expression underpins a host of cognitive and motor activities, of which only some are related to language.
As proof, consider this. The cognitive abilities of those with the defective gene imply that, while the FOXP2 holds sway over certain functions necessary to language production, it has peripheral or no effect on others. This leaves me with the impression that there's more to language than the FOXP2 gene, and that the gene has probably played other roles at earlier times in hominid phylogeny. To quote Lai, et al. again
Although the mean non-verbal IQ of affected [persons] is lower than that of unaffected [persons], there are affected individuals ... who have non-verbal ability close to the population average, despite having severe speech and language difficulties; therefore, non-verbal deficits cannot be considered as characteristic of the disorder [emphasis added].From this I conclude that the relationship between the FOXP2 gene and Neanderthals, and between the FOXP2 gene and language are not, by any means, straightforward. Lai et al. summarize their findings this way
Individuals affected with developmental disorders of speech and language have substantial difficulty acquiring expressive and/or receptive language in the absence of any profound sensory or neurological impairment and despite adequate intelligence and opportunity. … Our findings suggest that FOXP2 is involved in the developmental process that culminates in speech and language [emphasis added].Thus, it appears as if the Neanderthal and modern human synapomorphy--the FOXP2 gene--is not, on the evidence, the end-all and the be-all mechanism that gave rise to modern human linguistic ability. [Think about it. The affected individuals must still retain a semblance of linguistic ability despite their disability. How else could they understand enough about the intentions of the testers to respond in any meaningful way in test situations in the first place?]
The Levallois Technique? The final issue that I want to take up with respect to Tom and Fred's thesis is the idea that Neanderthal cognition must have been fairly sophisticated, given that they worked stone using what's known as the Levallois technique. Some of you will remember that I have serious doubts about the reality of this so-called technique of flint-knapping, mostly because I suspect that it represents a 'reified' category.
[Those curious about my stance with respect to the Levallois technique should scroll down this page until they see the 'Search SA and Linked Pages' widget in the sidebar, type in Levallois and press 'Search'.]In other words, the technique only exists in the minds of the people who've constructed their reality such that the so-called Levallois flake is the end product of a carefully orchestrated set of numerous decisions and flake removals designed from the outset to knock off a final flake of a given form. I've called the notion of a Levallois 'technique' preposterous, and I stand by my assessment. Unfortunately for Tom and Fred, their impression of the Neanderthals' cognitive abilities are grossly inflated by the phantasm of the Levallois technique. Without a Levallois technique, the Neanderthals, when all is said and done, break rocks into smaller, sharp rocks, and often enough break even smaller pieces off the sharp rocks to keep the edge sharp. Not a lot, I think, on which to base a theory that depends on the enormous cognitive abilities of the Neanderthals.
I'm certain that those reading How to Think Like a Neandertal will find it fascinating and informative. But as you can imagine, if I were you I'd hold off thinking that this work is the end of the story.