Richard Dawkins

There's not much difference between them.

Now, you might expect that if it was like, you might expect a climb that you would gradually get as you look from, these are very closely related species.

As you go from west to east, the call will get gradually deeper and deeper and deeper.

That's what you might expect.

The reverse happens.

It's a reverse climb.

As you get into a zone of overlap,

the Olivacea call goes up and the Pteranensis call goes down, so that these creatures are exaggerating the difference between them.

So in the zone of overlap, the difference between them is exaggerated compared to where they don't overlap.

This is equivalent to migrating into the Glasgow pub and attempting to do a Scott's dialect and being

And being hit.

And being jumped.

Yes.

And I think it's probably true.

I mean, Dobzhansky had this theory that when new species form, when an ancestral species diverges to form new subspecies,

and then new species.

There is an intermediate and interregnum when natural selection favors anything to differentiate them, anything to make them sound different or look different or smell different, to exaggerate the difference.

And so there is a kind of acceleration of the speciation process.

Well, drift is, in a way, the opposite of natural selection.

Evolutionary change can come about through drift.