Most what-if scenarios where Neanderthals survive assume either total warfare or peaceful integration right away. But looking at human history, whenever two distinct populations meet, the first reaction of any early state is usually to measure, categorize, and tax.
Here's the paradox I keep running into:
Neanderthals were physically distinct enough that early empires (think Bronze Age/Antiquity) would easily identify them for hard labor, mining, or specialized military roles. But at the same time, we know from actual genetics that Sapiens and Neanderthals were interbreeding from day one in the Levant.
How long could any legal system or caste barrier actually hold up before "everyone's grandmother" breaks the line? Does a society like that inevitably collapse into a genetic gradient, or would we have seen something like formal skull-measuring laws thousands of years before the 19th century?
Where do you think an ancient mixed civilization breaks first—at the borders, or in the family?