Question: How has evolution shaped the human species to use language?

Joseph Devlin answered on 17 Mar 2010:

That’s the 64 million pound question! No one knows the whole answer, but I’ll try to provide a partial answer.

Evolution has endowed humans with many different biological traits that are crucial for language. Some of these are changes to the body and some are specific to brain. So let’s consider bodily changes first.

One of the core things that let’s us speak is the fact that we walk upright. When on all fours, muscles on the torso that are needed to control breathing are used in basic locomotion (try holding a conversation while doing press-ups – it’s hard!). There were other changes to breathing that allow us to control it consciously and that too is vital to speaking.

There have also been many changes to our mouths and throats that are critical for speaking. So we have incredibly nimble tongues that are not found in any other primate. This is partly because of the shape of our mouths (less long snouts give more room for the tongue) and changes to the voice box (larynx) which has descended in human throats much deeper than in other species. All of these changes mean we can make a much larger set of sounds with our mouths than any other mammals. Obviously, you need to be able to do that or vocal communication just becomes a bunch of shrieks and grunts as it is in chimps or bonobos.

At the brain level, there must have been several changes that allow us to do things that are uncommon in most species. For instance, very few species are vocal learners – they can’t learn to produce sounds to match those in their environment. Song birds are the obvious exception but dolphins, orcas, and elephants also do this although no other primates (apes, monkeys) can. We need this ability to learn to produce words, which are obviously critical for language.

We are also very good at organising our use of language so that we can convey complex ideas that are easily understood. So sentences have subjects and verbs and sometimes objects and there are many grammatical clues to who is doing what to whom. If I just produced an unordered set of words:

me banana banana

you might interpret this as me wanting a banana although I could have been saying,”I see a banana” or “I am a banana” or many others. The fact that we have this ability to use grammar is arguably what sets us apart from all other species because it means we have proper language and not just sets of unordered words.

If we knew what changes had occurred to our brains that allows us to do these things, we’d be well on our way to understanding some of the fundamentals of what makes us human. For me, that’s an interesting enough question that it drives essentially all of my research.