A really good example in how poorly race represents what it seems to represent is that the two ethnic groups with the most genetic distance from each other are

A really good example in how poorly race represents what it seems to represent is that the two ethnic groups with the most genetic distance from each other are both "black." In fact there are dozens if not hundreds of african ethnicities with as much difference between them as, for example, irish and japanese have. But since they all have the dark skin phenotype, they all register as one "race." It's just not a useful system for much.