Note: This entry replaces an earlier entry which has been de-published.
The controversy over the article by Dediu and Ladd on a possible connection between genes and tones has been simmering the past few weeks.
However, I do compliment Robert Ladd for doing outreach to the linguistic community. He’s posted his own commentary site and contributed a guest post to Language Log. It’s clear that he understands some of the implications of what he’s claiming for language theory.

• Language Log
• Ladd’s Summary

He invited linguists to write comments and I took him up on it. Still I remain skeptical, if more neutral. Here are some of my comments to his hypothesis.

Differences in Linguistic Ability?

It’s clear that individuals differ in their ability to speak and use language, but Ladd is proposing that there could be subtle differences across populations. On the other hand most linguists tend to believe that language ability is the same across populations. That is, an average child of Asian descent has the same ability as a child of European descent.
Where does the original assumption of equal language ability come from? It’s rooted in the observation that an infant typically gains the ability to become a native speaker in whatever language he or she is exposed to. Immigrant children coming to the US gain native speaker proficiency in English. More crucially, European children living in China can gain native speaker like proficiency in tone languages. A famous example is American author Pearl Buck.
Another aspect is that children tend to acquire language at the same rate, and in the same order. In most cultures, it is expected that five year old children can speak with a certain level of proficiency. In order for this to be the case, the assumption has been that language has to fit within certain parameters. I would expect that tone languages would fit within those parameters. If it didn’t, I think you would expect that European children would have significant delays learning language.
Ladd says he will be conducting experimental studies to determine if this is the case. However, I would object to characterizing the “equality of languages” as dogma. It’s a reasonable assumption given what we know about language acquisition in general.

Neighboring Tonal and Non-Tonal Languages

Ladd claims that the genetic propensity for tonal languages would be subtle. How subtle?
There are many cases of East Asian speakers NOT having a tone language. Mongolian and Manchurian are non-tonal and are spoken by “Western desert barbarians” (the kind of people the Great Wall of China was trying to keep out). Yet both a Mongolian dynasty (Ghengis Khan) and a Manchu dynasty (Qing dynasty of the “Last Emperor”) were established in China. We know Ghengis’s DNA got into China as well Manchurian DNA. Yet the tonality of Chinese has never wavered in that time…nor have Mongolian and Manchurian appeared to have moved to being more tonal.
Yet Ladd is predicting that one of the populations should have drifted either towards tonality (if they have the tone genes) or away from it (if they’re missing it). Instead the [±tonal] distinction has been in place in each language family for centuries if not millennia.
Another question is if a language with a Middle Eastern or European population could be tonal. Well Ladd’s map identifies one tonal language in the vicinity of Iran, and that is well within Middle Eastern “non-tonal” territory.
The predictions, if any, would be extremely weak.
It would almost be like saying that because many people of African descent have the ability to excel in basketball, it should have been invented in Africa. The reality is that was invented by an Anglo Canadian (James Naismith) in the US, and that it is played by people of all ethnic backgrounds.
You might be able to predict the line-up of the NBA, but the sport itself is enjoyed by people of all populations.
P.S. Speaking of Ladd’s map – what’s the tonal language of Japan? Ladd’s text excludes Japanese because it’s “pitch accent”, but it can’t be Ainu either.

What Tonal Advantage is There?

It’s not clear what advantage the tone genes would give you.
I’m not sure it’s a perceptual advantage. The inventory of the English intonation system (as itendified by Pierrehumbert 1980) includes both simple tones (H,L) and complex tones (*LH, *HL, etc) – the difference is that they are distributed across a sentence or phrase…and that we do not use tone to distinguish different types of vocabulary items. But English speakers regularly use differences in pitch to determine speaker focus and mood. It’s not a universal intonation system either – non-natives have to be trained in it (see Learn English intonation)
It would have to some sort of switch in the phonological system that says “we can do phonemic tone” but again how does this interact with the ability of Pearl Buck to acquire a tonal language?
Or does it have to do with tonogenesis (the creation of phonemic tone)?

Origin of Tones

There are cases where we can see tones coming into a language. One is a dialect of Kammu (Svantesson & House, 1996).
In this case, the non-tonal dialect dialect distinguishes voicing (level of vocal cord vibration) in the initial consonants, but the innovative tonal dialect has reinterpreted that as tone.

As it turns out, this is pretty much how all documented cases of tonogenesis works. A population reinterprets a distinction in vocal cord vibration for voicing or aspiration as a difference in pitch. This type of sound change where a sound is reinterpreted is not that unusual. For instance French nasal vowels are reinterpretations of vowel+nasal.
An interesting question is if the tone genes affect how you hear voicing NOT tones per se. Can a Middle Eastern or Asian language go through the same tonogenesis phenomenon?
Apparently Punjabi (related to Hindi) is classfied as a tonal language. It’s population is in Northwest India, so is probably mostly “Middle Eastern” (it’s relatively close to where the Indo-European speakers probably came into India)
So the answer is…yes?
So my conclusion on Ladd’s hypothesis is still – I just don’t think so.