This doesn't explain how clothing was made in earliest times. How did people wear anything at all, besides animal skins? Lots of Native American tribes didn't seem to wear much. And uncontacted tribes today, either.
He does mention the Native Americans' typical use of "buckskin" in his prior post about the Dothraki's relation to historical steppe peoples (https://acoup.blog/2020/12/04/collections-that-dothraki-hord...).
That's more Hollywood than history. Look at real photographs and many of them will be covered up completely except for the hands and head.
We all came from Africa, along the equator. Leaving that environment put special pressure on homo sapiens, including adapting culturally to extreme temperatures.