It's safe to say people around the world freaking love avocados. In the United States alone, 4 BILLION of these slimy green potatoes were consumed in 2014, and over in Australia, we eat so much of them, we're going through waves of 'national shortage' scares.

It's not hard to see why we're so obsessed with avocados - they not only taste great, and can be used in everything from salads and sandwiches to nachos and sushi, they're also extremely good for you.

They're high in fibre, monounsaturated fatty acids, antioxidants, vitamin B6, vitamin E, and a bunch of healthy fats, and they're packed with twice the amount of potassium as bananas. But here's the thing - avocados shouldn't even really exist.

As the SciShow video above explains, avocados are the way they are, with their large, bulbous shape, single giant seed, and tough outer skin, because they evolved to be eaten by enormous, prehistoric animals tens of thousands of years ago.

During the Cenozoic era, huge megafauna such as mammoths, horses, elephant-like gomphotheres, and giant ground sloths (some of them weighing more than a UPS truck, says K. Annabelle Smith at Smithsonian) thrived throughout Central and North America, and they ate a crapload of avocados. 

This ended up being a very beneficial arrangement for both the megafauna and the avocados - the megafauna got to eat something that was large enough for them to actually taste (imagine feeding a strawberry to a tractor), and the avocado seeds were distributed over large distances via their poop.

But things got very dangerous for the avocado when this perfect distribution method started to die out. As Smith explains, the great mammals of the Western Hemisphere started to disappear about 13,000 years ago, and North America lost 68 percent of its megafauna species, while South America lost 80 percent.

Without a mechanism by which these plants could disperse and proliferate, they should have gone extinct too, but for once, humans did right by a threatened species. 

Turns out, the prehistoric farmers of the Aztec civilisation took it upon themselves to 'save' the avocado, and even gave it a very special name to match its very special status of the fruit that lives in our hearts - ahuácatl, wwhich means testicle. Yep, humans have had a dumb sense of humour for pretty much ever.

These farmers obviously knew a good thing when they saw it, because just as avocados were the perfect food for truck-sized animals, their high-fat and high-protein flesh was the energy boost the Aztecs needed.

Watch the video from SciShow above to find out how our ancient ancestors did us one of the biggest favours ever - delicious snack-wise, and watch below to see why fruit doesn't get much better: