How much of human language is wired into our brains and part of the heritage of our biological evolution? How much is a product of our culture and learned in childhood? This is a long-standing question, and an important part of understanding ourselves.
A good way to approach this question is to look for linguistic universals. A universal is something that is found in (almost) all languages.
It is an odd use of the word that universals don’t need to apply quite universally. While odd, it is fairly sensible for three reasons. First, there are a lot of languages out there, and many of them haven’t been studied very carefully. So, we don’t really know all the world’s languages. Second, there are many languages that have just gotten a season or two’s fieldwork by a graduate student, and a few of those quick studies will have reached the wrong conclusions. So, the term has to allow for some mistakes.
The third reason is more subtle and interesting: culture can sometimes override biology. Oh, not for everything: a cultural decision to breathe water woudn’t cause it to happen. It’d just cause everyone to lie about it, as one sees in Stanislaw Lem’s book “The Star Diaries” (Mariner Books (1985) ISBN-10: 0156849054, ISBN-13: 978-0156849050). But sometimes our physiology doesn’t constrain us completely: it just makes one behaviour easier/faster/better than another. That’s the interesting middle ground where culture can sometimes override biology, but you can still have a universal preference for one behavior over another.
The logic behind the connection between universals and the nature/nurture question is that human biology is fairly uniform, so that biologically constrained aspects of language would be expected to be much the same from one language to another. Shared features are not proof of a biological origin since culturally determined aspects can spread due to contact, trade and politics.
However, any uniformity we see carries a suggestion that biology is important. To pick one example, Martian linguists visiting the Earth might reasonably guess that the universal fact that females speak with a higher fundamental frequency than males is caused by an underlying biological difference. And, of course, they would be correct, even though there are a few high-pitched males and low-pitched women.
On the other side of the coin, substantial differences in linguistic implementation are strong evidence for the importance of culture. We can be fairly certain that there is no biological basis behind the word we choose to express the color blue. Once you get outside the family of related European languages, the word varies wildly.
Some of you may ask “Well, what about Chomsky and his Universal Grammar hypothesis?” All I can say is that it best interpreted as a metaphor for a mixture of biological and cultural factors. That hypothesis doesn’t seem to connect to modern neuroscience. It’s also a bit vague: how many switches are there? What do they switch? And it hides a lot of its limitations under the rug, under the guise of distinguishing between performance and competence. This may be the subject of a future blog post.