Let me introduce you to the Laurentide ice sheet [1]. It was similar to the ice sheets that now cover Greenland and Antarctica and was up to 2 miles thick in pl

Let me introduce you to the Laurentide ice sheet [1]. It was similar to the ice sheets that now cover Greenland and Antarctica and was up to 2 miles thick in places, extending far south into what is now the US. After being around for ~2.5 million years it melted about 20,000 years ago. Prior to then sea levels were ~130 meters lower than they are now. Think about that. There was still various land bridges that allowed migration. We see direct evidence of this. It's why, for example, we find archaeological sites under the English Channel (eg [2]). So our ancestors like migrated along and settled on coasts and rivers. Obviously we have a lot of evidence along rivers because they weren't inundanted by 130m of water but the coasts were. So that means a lot of that evidence was simply erased. We always have to take that gap into account (eg an inland people from Siberia migrating to North America will have had all of its coastal history erased so the first we'll see of them is when they advanced to the point of settling inland). [1]: https://en.wikipedia.org/wiki/Laurentide_Ice_Sheet https://en.wikipedia.org/wiki/Laurentide_Ice_Sheet [2]: https://www.livescience.com/1759-stone-age-settlement-english-channel.html https://www.livescience.com/1759-stone-age-settlement-englis...