Human raiment is not typically preserved in the fossil record, so researchers have turned to lice genetics for hints. Body lice diverged genetically from other louse species about 100,000 years ago. Because body lice live primarily in our clothing, scientists use that moment of differentiation as the likely era when humans started dressing themselves.
It's possible, however, that humans started wearing clothes even earlier. We know that pubic lice jumped over to humans from gorillas—our genetically distinct head lice migrated from chimpanzees—about 2 million years ago. And since pubic and head lice probably couldn't have coexisted on the same body if there was a hairy highway connecting their favorite anatomical spaces (one would have beaten out the other for all the available resources), it's likely that we had lost our body hair by then. Some claim that humans donned clothing shortly after that, but others argue that there's no reason our ancestors would have needed clothing in steamy Africa.
Link | Photo: US Department of Energy
It might not be clothing by our standards, but anything you wear is technically "clothing" in my book.
Perchance it wasn't even a matter of warmth. We know some of the first clothing worn was made from leather. Leather protects from abrasion, animal attacks, etc. It basically provides us with a tougher hide.
If animals had the skill to make and wear things, they would. They do know how to keep warm, how to stay cool and even help each other get rid of lice and such. They aren't stupid, just limited as too what they can make.
What would it say if they found a human with chimpanzee head lice in his pubes?