in a burrito, people seem to love avocados.

In fact, people in the United States munched through four billion of them in 2014 alone.

They taste great, they’re good for you -- but one of the most amazing things about avocados

is that ... they still exist.

See, they had a special relationship with huge beasts that lumbered around Central America

tens of thousands of years ago.

And when these animals went extinct, avocados could easily have gone down with them.

But, luckily for us, they were saved by some prehistoric farmers.

The word ‘avocado’ comes from the Aztecs. Specifically, the Nahuatl word ahuacatl, which

means ... testicle.

I mean, you can kind of see where they got the name -- it probably has something to do

with the, uh, you know the shape and texture of avocados, the way they hang from trees.

Anyway, before they became popular in the rest of the world, they were cultivated in

Mesoamerica for thousands of years.

Avocados are a fruit – basically, swollen plant ovaries.

But, nutritionally, they’re very different from other fruits you’d find at the supermarket.

Fruits like apples and oranges are composed mostly of water and sugar.

And in general, fruit is probably better for you than, say, a bag of sweets or a sugary

drink because it contains fiber, which slows down sugar absorption and makes you feel fuller, faster.

By comparison, avocados have much less sugar but more protein and fat. That gives them

that smooth, creamy texture, but also puts them on the calorific side – for a fruit,

anyway.

They also contain high levels of potassium and folate nutrients, as well as vitamins

C, E and K.

And technically, avocados are berries, like grapes and blueberries.

Rather than holding lots of little seeds, the avocado goes all-in on one big seed – that

massive ball at the core of each fruit.

And avocadoes, with their huge seeds, evolved alongside equally huge guts.

Tens of thousands of years ago, during the Pleistocene Epoch, a menagerie of megafauna

-- or, giant animals -- roamed the Americas.

While woolly mammoths chilled out in the North, ground sloths weighing three tons and armadillos

the size of cars lived in the warm equatorial forests.

And these giant sloths and armadillos ate a lot of avocados.

Their digestive systems would break down the tough skin and absorb the high-energy pulp.

Then, the indigestible seed, which contains bitter toxins that kept the animals from chewing

it up, passed right out the other end.

The animals got a tasty meal, and the avocado trees got to scatter their offspring throughout

Mesoamerican forests.

Plus, the seeds got some nice, warm fertilizer to give them a nutritious boost.

And with these megafauna around to eat the fruit, avocado trees could keep growing berries

with increasingly massive seeds.

The bigger the seed, the more nutrients could be stored inside as a “starter kit” for

the baby tree.

This is especially useful in dense, tropical forests where canopies of older trees block

out much of the light from the saplings below.

So instead of depending entirely on sunlight for energy, the avocado seedlings could supplement

photosynthesis with the nutrients in their seed to survive.

This happy evolutionary match didn’t last, though. Eventually, the megafauna suffered

a mass extinction around ten to thirteen thousand years ago.

We don’t know exactly why, but scientists think the warming climate at the end of the

last Ice Age was partly responsible.

Though it was also suspiciously close to the time humans began spreading across the Americas

-- no doubt enjoying lots of giant-mammal meat along the way!

This meant avocados were in trouble.

Without their large-gutted evolutionary partners, the trees stopped thriving -- their fruit

fell to the ground, and the seeds mostly just became food for mold.

But more hungry creatures were nearby!

The new human arrivals loved the avocado’s flesh as much as the ground sloths did. They

also had the tools to eat them, and the brains to figure out how to grow them.

Avocados were all set for domestication.

The avocados we eat today are probably a little different from the ones that grew tens of

thousands of years ago -- for example, thanks to artificial selection, they probably have

more pulp than their ancestors.

But they’ve kept their huge seeds, ready and waiting for the guts of long-dead beasts.

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