Roughly 165 million years ago, a squirrel-like creature called Megaconus was scurrying around in what's now northeastern China.
But Megaconus wasn't a squirrel, or even a mammal—it belonged to a group of mammal relatives that lived before all modern mammals did.
So, when scientists found impressions of fur — a defining feature of mammals — surrounding the fossil remains of Megaconus, they knew that fur must have a deeper history than we thought.
But despite its long evolutionary history in mammals and their relatives, a coat of thick fur is one thing that we humans don't have.
In fact, we're the only primate without it.
So there must be a really good reason for why we roam around … basically naked and unusually sweaty.
It turns out that this small change in our appearance has had huge consequences for our ability to regulate our body temperature, and ultimately, it helped shape the evolution of our entire lineage.
Despite what you may have heard or thought, fur and hair are actually the same thing.
We just use a different word to describe the fur that we have.
But they're both the same kind of pelage, or hairy body covering.
