I don't know if she was consciously trying to evoke real world racism and tropes, so much as to create a context where the concept of 'racial' prejudice existed - the quote to me suggests that was exactly what she was trying not to do. She wanted to make it more abstract, not root it in something concrete. I'm not arguing that she was successful in creating that distance, and I agree that the assumptions of the time regarding the appearance of archaic humans (stereotypical northern European) and neanderthals (overall darker) were pretty problematic, and that affects the book for sure. But I don't think she should be taken to task for the general description of neanderthal body types as stocky, sloping brows, etc.

There's a catch 22, as racist depictions of PoC often explicitly attribute them neanderthal-like traits. But it's not the neanderthals' fault for actually looking that way!