Right-handedness, lateralization and language in Neanderthals: a comment on Frayer et al. (2010).

A lot of ink has been spilt in Paleoanthro-pology in discussing whether or not Neander-thals possessed complex language (which means " human language in the modern sense " , quoting Arbib, 2005, p. 21, that is, a representational and communicative system with hierarchical and recursive structure), given their phylogenetic closeness to modern humans. Recently, Frayer et al. (2010) (this journal, vol. 88; henceforth, F) have found that Neanderthals had a right-hand-edness ratio " similar to living people " (F, p. 113). This leads them to infer that this species had a pattern of brain lateralization resembling ours, and, ultimately, that " Neandertals (and, very likely, their European ancestors) had linguistic capacities similar to living humans " (F, p. 113). It is not our intention to cast doubt on F's remarkable finding. However, the point is made that their inference according to which Neanderthals had complex language is questionable. Some reasons will be brought to the fore. To begin with, " there are some drawbacks in determining hand preference from tooth scratches " (F, p. 115; see Bax & Ungar, 1999, who question the link between hand-use and teeth striations). In addition, other types of evidence (such as tools) could be more suitable for inferring whether extinct hominid species showed laterali-zation of motor tasks, given that in our species (and in great apes, in general) handedness is correlated to task complexity, as discussed by Uomini (2009, pp. 413-414, 416 and ss.). Leaving that aside, the relationships between right-handedness, (structural and functional) brain lateralization, and language are perhaps not significant enough, or illuminating from an evolutionary perspective. In our species, a positive correlation exists between general verbal skill and precociousness of language development on the one hand, and the degree of lateralization in hand use, on the other (in general, between lateralization and cog-nitive abilities, including language). However, that correlation is responsible for a variation of about only 1% in both the General Ability Index and the Intelligence Quotient; the same applies to the Quotient's verbal component (Nettle, 2003). Hence, Natsopoulos et al. (2002, p. 223) claim that there is not a " significant association of language proficiency with variations of lateralization regarding hand-preference and hand-skill ". It becomes even more relevant that in about 30% of left-handed people, the corti-cal areas related to linguistic processing are not so lateralized to the left hemisphere (Foundas et al., 2002). In addition, and crucially, …