"Races do not exist" ...

or "are social constructs"

What the fuck does that even mean? It is pretty obvious that they do. I seriously do not get it. Does anyone here have the knowledge to defend these seemingly ridiculous statements from a scientific perspective?

First year human geography class, in one of the lectures we were taught all about the racist myth of the existence of races.
According to my lecturers, there really is no such thing as race; there are not genetic differences that make one population different from another.
Of course, university lecturers know what they're talking about, so I've come to the conclusion that the japanese, the indians, and the english, etc, all look different to one another due to magical forces caused by some kind of god.