One of my professors in college called horses the world's first solar-powered vehicles.

His argument was that horses take energy from the grass, which took it from the sun.

And so, from a human's perspective, a horse was literally a vehicle running on converted solar energy.

A bit of a stretch, maybe a bit of a cheeky line, but fun to say.

The truth is, if you want to call horses the world's first solar-powered vehicle,

if you set the bar that low, you've basically got to admit that almost all organisms on Earth

are in some sense solar-powered.

Most organisms get energy from the sun,

whether directly or indirectly. There ain't a lot of ways to get energy on this planet, and

almost all of them are solar. Unless you're a specific species of ape with access to technology

that extracts energy from weird stuff like the movement of rivers or the splitting

of atoms or whatever, or if you live near a hydrothermal vent, on 99% of the planet,

you've typically only got two options. You either get energy from the sun, or you get hand-me-down

sun energy through the consumption of other species.

Every single creature I've done episodes about falls into the latter category. This show never

leaves the animal kingdom, and, again, excluding one species of ape, the game we play in this

kingdom is eat other organisms and take whatever energy they've accumulated.

You eat organisms that get energy from the sun typically, or eat other animals that do that,

or even eat animals that eat animals that do that if you're a real tough guy.

Today, I'm going to talk about one of the only animals that falls into the former category,

an animal that doesn't get hand-me-down sun energy but takes it straight from the source.

The leaf sheep.

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