Richard Dawkins

Okay, so suppose one vowel shifted for some reason...

then that might have caused a necessity for other vowels to shift in order to disambiguate because there might have been confusion resulting from the first vowel shift.

Could the whole series, a cascade of vowel shifts, have followed for functional reasons disambiguation?

What I don't understand is why North Americans don't differentiate between can and can.

Because we don't have to.

You do, because cannot, they're the exact opposite of each other.

Okay, well, we'll have to agree to differ about that.

Look, I want to ask you, I want to challenge something.

What?

Okay.

Proto-Indo-European, supposed to be the ancestor of a very large number of languages, all European languages except Basque and several Indian.

Well, in evolutionary biology, it is a fact that if you take any two animals you like, like, for example, you and a kangaroo,

There is a single individual animal which is the most recent common ancestor of you and a kangaroo, and that's an individual.

I literally mean an individual.

There was a mother animal, looked a bit like a shrew or something like that, which had two children.

playing together in the dust and one of those children became the ancestor of humans and the other of those children became the ancestor of kangaroos.

That is literally true, an individual.

Now I suspect that linguists suffer from, well, you've heard the phrase physics envy, academic disciplines.

Envy physicists.

Well, I suspect that linguists envy biologists this ability to trace back to a single ancestor.