Evolution, Emotion, and Language

In a study on Meerkats in the Kalahari Desert, a team from the University of Zurich found that young meerkats respond to vocalization information about “threat urgency” (via tone) earlier than “threat type” (via variation in vocalization) as compared to older meerkats who can distinguish both pieces of information. The researchers argue this association between tone and urgency/emotion is hard-wired. This interests me because primate vocalizations have been studied extensively. For instance, the ververt monkey has eight different vocalizations for threat, each one referring to a different type of predator (such as chattering teeth for a snake). If the findings of the meerkat are observed in additional species, detection of emotion (as they interpret urgency in utterance) might indicate an evolutionarily conserved trait.

In a seemingly unrelated article from Scientific American, linguists at the University of Edinburgh have found a link between two genes (ASPN and microcephalin) involved in brain development and language in a study of 49 different populations. (The original study was published in PNAS this week.) The genes studied are active during embryonic brain development (influencing brain size). Developmentally, they may also serve a function in brain structure. Previous research has found no relationship between popular mutations of these genes and intelligence, social ability, and brain size. They appear to affect the cerebral cortex (which plays a role in understanding language). Researchers tested for a relationship between many genes and many aspects of language. They found a positive relationship between these mutations and language tone. Most languages fall into one of two categories (tonal or non-tonal). Exceptions include Japanese, some Scandanavian dialects, and Basque. Tonal languages are ones where the pitch of the spoken word makes a difference in meaning. Nontonal languages are ones where the pitch does not make a difference in meaning. The mutations date to about 37,000 years ago and are found in abundance in nontonal language speakers. Tonal language speakers do not have these mutations.

A note of caution in interpreting these findings from the article:

Northwestern’s Wong says that in a field in which researchers struggle to determine whether differences arise from experience or genetics, the new study “gives us an idea that there is a genetic side to things.” He says the research indicates that small differences in brain organization determined by genetic makeup may be amplified by cultural factors and contact with other languages through war or migration, creating today’s dichotomy in language tonality.

“Even remarkable correlations can arise by coincidence—or, in this case, possibly by prehistoric migration factors that are currently unknown to anthropology and archaeology—so we can’t rule that out,” Ladd says. “The next step is to attempt to correlate individual genotypes with measurably different behaviors on experimental tasks that are plausibly related to language and speech.”

The latter study has many components that require further study but the initial findings are interesting especially in light of the meerkat findings. This developmentally early comprehension of tone is likely to be evolutionarily conserved in mammals (dating back to a mammalian common ancestor and not lost in the majority of subsequent species derivations). So, if we accept the findings of the linguistic study for heuristic purposes, tonal languages would be ancestral to nontonal languages since nontonal languages are associated with a recent mutation and tonal language speakers lack it. But, this is counterintuitive to the meerkat study (that already has a strong base of supportive research). Why? If tone is evolutionarily conserved because it is associated with fitness, or net reproductive success (here, survival via an ability to perceive urgency of threat and, thus, escape predation), then alterations to the meaning of tone would interfere with its function as a vehicle for emotion, urgency. Tonal languages innovate a new use for tone. Rather than urgency, tone now conveys a difference in meaning. But, with what little linguistic knowledge I have, the tonal languages that I am aware of are older than nontonal one (ex. Chinese is tonal and English is not).

I know I am linking the findings of two unrelated studies. But, so much of what occurs in the science research today lacks context within and across disciplines. By lack of context, I mean a failure to contemplate evolutionary meaningfulness. I expect case studies in smaller specialized journals to disseminate current research findings to the discipline but in a larger journal like PNAS, I expect more context.

So, that said, I wonder if this finding, after further exploration and testing, will actually be supported as a valid relationship (e.g., one that has meaning as opposed to one that is coincidental). At the very least, it presents interesting data to those interested in this growing gene-culture approach to prehistory (with language representing genes) and population migrations.

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