Hair...

 It's one of our stranger features. No hair on our bodies, lots on our heads. No other animal, including our close relatives has this pattern.

And it varies a lot in texture.

So, why do we have hair? Turns out it's to keep our advanced brains cool.

And it turns out the most efficient design for cooling is 4C. Yeah, we now know for sure what many have long theorized...Black people have curly hair as a means of temperature regulation.

https://www.iflscience.com/we-might-finally-know-why-curly-hair-exists-67605

Well, it's still needing more work, but it makes a lot of sense. I would also want to see if straight white hair reduces heat loss from the cranium...i.e., did we go back to having straight hair when we left the tropics.

(Also, it may be a Neanderthal trait).