For 50 years, biologists have been capturing and recording Darwin's finches in every minute detail, and they've revealed something that would amaze Darwin-- the speed of change.

[Birds chirping] This is the guy to tell us all about it, one of the latest to dedicate their life to the birds-- local scientist Jaime Chaves.

[Jaime] For any evolutionary biologist to have even the chance to be on the Galapagos to study finches is kind of a gift.

[Campbell-Staton] Speaking to him, it's hard not feel a little jealous.

[Jaime] I'm just amazed by the amount of data that these little birds have been producing.

[Campbell-Staton] Nothing like a bit of data.

[Jaime] The difference between these two birds is the beak sizes.

So, this bird on the right-hand side has a smaller beak compared to this one on my left, although being both from the same species.

[Campbell-Staton] These tiny variations can mean the difference between life and death.

[Jaime] Almost 1 millimeter in beak length.

That maybe doesn't sound too big, but a dramatic environmental event can wipe out half of the population, because those birds didn't have the beak shape to respond to that dramatic change.

[Campbell-Staton] You don't need a whole different island for evolution to take place.

The data now show that all it takes is a big enough driving force, like a severe drought, and beak shapes can change almost overnight.

[Jaime] Evolution on the Galapagos is actually very fast.

We can actually measure how much evolution can happen between year 1 and year 2.

[Campbell-Staton] So, there you have it.

Chuck had it not quite right.

It turns out, a biological change can happen in a matter of just years, not millions of years like he thought.

You know, that's a radical shift.

And amazingly, biologists like Jaime are getting to watch it unfold before their very eyes.