Around 35 million years ago, Earth was populated with giant, prehistoric ground sloths like Megalonyx jeffersonii (named after Thomas Jefferson), Paramylodon, and Megatherium who, until around 10,000 years ago, roamed what would become the Americas.

Today, there are six extant species of sloths in the trees of Central and South America, and they’re famous for moving slowly. But why do they take their time? And why might we thank their extinct ancestors for avocados? This TED Ed reveals some history and biology of this arboreal folivore.

Watch more sloth videos on this site, including The Pygmy Sloths of Isla Escudo de Veraguas, Robot ‘Spy Sloth’ Meets Real Sloth, and a pygmy three-toed sloth swims.

PS. What do baby sloths sound like?

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