Despite various promising avenues of approach there is really nothing we can know about the way language evolved, so we should be silent on the subject, a Spanish anthropologist Camilo José Cela Conde, told the participants at the Evolang conference which began meeting today (March 12, 2008) in Barcelona. The evidence we have (fossil and molecular) is too ambiguous to support clear statements.
The text he used to start his presentation came from Wittgenstein, “Whereof one cannot speak, thereof one must be silent.” Cela Conde then asked what we could say about the evolution of language.
To find an answer he announced a “hypothesis,” which in presentation began to seem more like an axiom: Language is a human apomorphy.
A what? An apomorphy is a technical term used in evolutionary studies to indicate a group with a distinguishing trait. Cela Conde defined the term to identify a “derived trait, not present in the sister-group.” While it is possible to argue with his definition, the argument would be pointless. That is what Cela Conde took it to mean, and that is what he was talking about. More subject to challenge was his assertion that Neanderthals constitute a “sister-group” that lacked language. This assertion was widely questioned in the discussion that followed.
Having asserted that language is a human apomorphy, the speaker went on to list ways to analyze apomorphies. Each method was then examined and disposed of in the same way. Cela Conde would cite initial enthusiasm for the method and then more recent skepticism. The skepticism was accepted as decisive and the method was rejected.
Cela Conde first used this approach to reject the search for fossil evidence concerning the shape of the human vocal tract, with the idea that the more human-like the vocal tract, the more human-like the vocalizations:
- Some people have supposed that the descent of the larynx in the human throat, a process that begins at about three months of age, might provide a good clue. But Cela Conde rejected that idea by quoting Jean-Louis Boë to the effect that monkeys have the same vocal-tract as newborn humans, but the monkeys cannot talk because their brains are not up to it.
- Another hopeful clue might be the hyoid bone which enables humans to control their speech and which was identical in shape in Neanderthals. But Philip Lieberman says you cannot use the hyoid bone to determine the vocal tract’s shape.
- Finally, we can consider the “flexed basicranium.” That’s the peculiar way the underside of the human skull is bent. At first Liberman thought this anatomical uniqueness was an important clue to evolving the modern vocal tract, but he later concluded that the bending cannot tell us about differences in the vocal tract.
In brief, we cannot determine from the fossil evidence what the vocal tracts of the human lineage and “sister groups” were like, so we cannot use them to determine facts about the evolution of vocalizing equipment.
Another piece of fossil evidence that was dismissed in the same manner concerned the expansion of the brain. The fossil evidence is very clear that starting with Homo habilis and continuing up to the appearance of Homo sapiens, the brain has been getting bigger. But we cannot say how this expansion specifically helped language, and we do not know enough to make assertions based on the differences between human and Neanderthal brains.
Still more fossil evidence comes from the opening (“canal”) to let the hypoglossal nerve emerge from the skull to control the tongue. The human nerve is larger than that of other primates and it needs a large canal to pass through the skull to the tongue. So perhaps canal size is an indicator of speech. But a team led by David DeGusta found that you cannot use the hypoglossal canal’s size to predict the presence of language.
Well, what about the FOXP2 gene? It seems to be important to speech and evolved dramatically since the last common ancestor shared by humans, bonobos and chimpanzees. But that argument relies on “speculative assumptions” and, since FOXP2 was shared by Neanderthals it tells us nothing about language as a human apomorphy. Gary Marcus, who had just given the previous presentation, argued strongly that Cela Conde was being too dismissive of the genetic language, but Cela Conde stood his ground.
Cela Conde’s argument was very much in the spirit of a defense attorney’s summation. It took each piece of evidence separately and said that it was not good enough; there was still plenty of room for doubt. Prosecutors usually reply that taken as a whole the evidence supports one another and points to a common conclusion. Defense attorneys often win their case because the standard of proof is “beyond a reasonable doubt.” In science, however, no doctrine is ever beyond all reasonable doubt and all cases are circumstantial.
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