But that's racismResearchers have found that all humans have a tendency to treat people, not of their family, tribal, or social group, as less than human.

Which I've been saying for years, racism is a natural human instinct. It's nice to know a mainstream scientific publication is getting brave enough to start to address the question again, though with a few word changes so not to set off the alarm bells.
What humans call racism, a preference for individuals closely related in DNA and an aversion for individuals of differing DNA exists in many if not most other living organisms.