In television trials, experts often testify that a piece of evidence is “consistent with” some theory of a criminal case. The phrase consistent with does not contribute much to ending reasonable doubt, but it shores up a claim, or at least undercuts a counter theory. A recent paper in The Journal of Human Evolution presents evidence that is consistent with this blog’s working hypothesis that language in some form began 1.8 million years ago.
A study of the upper jaw bone (maxilla) of a Homo habilis dating from 1.8 mya found that the scratches on the teeth suggested that the creature was right-handed. [See: D.W. Frayer et al, “OH-65: The earliest evidence for right-handedness in the fossil record.”] The human brain is unusual in the way many functions are confined to either the right or left hemispheres. Different parts of linguistic activity are sorted into right and left portions of the brain, a process known as “lateralization.” The unusual amount of right-handedness in humans (9:1) is generally attributed to this lateralization of human brains. Thus, the theory goes, right-handedness is a by-product of the lateralization needed to support language. So, if you can establish that the human lineage was already right-handed 1.8 mya, you have pretty good evidence for language’s antiquity.
The paper is very modest in its conclusions, noting that a single fossil is not much proof of anything. It would require a much larger sample of H. habilis fossils to establish that the species was mostly right-handed, and we would need a better understanding of the relation between lateralization, handedness and language before we could insist we had fossils proving that language was in use almost two million years ago. None the less, evidence consistent with that argument is better than no evidence at all. The authors predict that “right-handedness, cortical reorganization and language capacity will be shown to be important components in the origin of our genus.” So keep an eye out for evidence supporting or challenging this idea.