This is the memory palace. I'm Nate Demet.

During the 300 million or so years of the Paleozoic era, life thrived,

largely in the oceans. Though later periods within it did see the first development of terrestrial

life, your ferns, your extra-large dragonflies. But the ocean was where the action was.

Perto crustaceans and arthropods and evolutions first stabs at a workable fish.

The apex predators were the nautiloids. We still have them today. You may have seen them

in the aquarium in a darkened tank, cast an in airy blue light to simulate their deep sea homes.

They are so strange, like ambulatory ram's horns, with a peculiar white eye and a beard of tentacles.

They are among the most alien looking creatures we have. A remnant of a time when the earth was a very

different place. There are six species of nautilides now, but paleontologists tell us that in the

Paleozoic there were many more, varying significantly, some tiny, some gargantuan relatively as far as

mollusks go. Some in that spiral-shaped familiar from natural history museums are their gift shops,

others oblong, or dagger-like, depending on whatever conditions, whatever available resources,

whatever competitive necessities shaped their evolution a quarter of a billion years ago,

some 2500 different species. Louis Pernell noticed somewhere missing.

He was crouching in the attic of the National Museum of Natural History in Washington, D.C.

New York City. Years later he wouldn't be able to remember why he'd wandered in, just that it was fun to poke around.

It must have been fun to merely move around after his last job, just across the mall at the National Gallery of Art.

He'd applied for several government positions, commensurate with his education and experience.

He was a college graduate, a decorated veteran of World War II, and he'd already held a couple of temp jobs in the federal bureaucracy.

But it was the late 1950s, and he was African-American.

And the only job he could get was as a guard.

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