Dr. Glen Jeffery

And I noticed here in California, people have got lots of wooden houses.

Let's stay away from that.

Got a lot of what?

Wooden houses.

To a first approximation, the spectrum of light that you get from an incandescent light bulb is highly similar to solar light, right?

So it covers almost the same range.

It's a smooth function.

We drift gently from short wavelengths into medium wavelengths into long wavelengths.

So in evolution...

We were wandering around in sunlight.

We then made the transition to fires producing the same light.

And that's quite interesting.

Where do we use fires?

We use fires as we move further north, as we come out of Africa, you know, as we move into... I mean, why did people, beyond me having come...

for this interview from Northern Europe in winter.

It's beyond me as to why they ever did that because it's grim.

But they had a light source that was very solar-like.

And so there was no issue there, I don't think.

So it's that really very dramatic change that happens in the early 2000s.

Your body has never experienced...