[shuckmaster]

why are humans so hairless compared to other apesAll humans alive today are directly descended from one very small tribe that lived on the beaches between South Africa and Ethiopia from 200,000 ya to about 80,000 ya after which a few of them crossed into Yemen and quickly covered the beaches all the way to Indonesia before being nearly extincted by the Toba explosion about 74,000 ya. It was only after glacier melt about 50-60,000 ya that they began to multiply and move inland up rivers. Nearly all the differences between these modern humans and other apes and other extinct hominids is directly related to a survival life style based on traversing an average of 40 or more miles a day constantly running up and down long narrow beaches and swimming the frequent channels between the beaches. Hair anywhere but the top of the head and a little patch covering the pubic area would be a restrictive nuisance that was selected out.

[MRMEAN]

about 74,000 ya. It was only after glacier melt about 50-60,000 ya that they began to multiply and move inland up rivers. Nearly all the differences between these modern humans and other apes and other extinct hominids is directly related to a survival life style based on traversing an average of 40 or more miles a day constantly running up and down long narrow beaches and swimming the frequent channels between the beaches. Hair anywhere but the top of the head and a little patch covering the pubic area would be a restrictive nuisance that was selected out.

So if we want to follow our evolutionary heritage, we should run/swim 40 miles a day...in the nude?

[Physicist]

All humans alive today are directly descended from one very small tribe that lived on the beaches between South Africa and Ethiopia from 200,000 ya to about 80,000 ya

There've been many bottlenecks in our history. How do we know that humans weren't hairless prior to 200,000 years ago?

My personal expectation is that hairlessness is an adaptation for heat regulation for long-distance running that went hand-in-glove with the ability to walk upright. (Why? To chase down game. It is said that no land animal can outdistance a well-conditioned human.) Accordingly, I expect that the adaptation goes back millions of years.

All of these ideas are mere speculations, however. I'll be gobsmacked if there is ever any solid evidence for any of them.