They are linked, but they’re talking about how modern race ideas are evidenced in racism. It used to be that Irish people weren’t considered white even though they largely have pale skin. Today that’s a very weird idea because of course Irish people are white. But that wasn’t the case when the US was getting a mass of immigrants. Yes, people were bigots hundreds of years ago. Yes, racism and tribalism are linked, but the sheer concept of being white, black, red, yellow, etc didn’t exist until relatively recently.