race is real in how it affects our lives and how people perceive it. however, its not real in an absolute sense. for example, there is absolutely no genetic marker for race. there are genetic markers for affinity in terms of genetic relation. and in many cases that coincides with phenotypical similarity. however, that isn't always the case.
the best example will always be the Admanese Islanders. They are a small seculded tribe of people who live in a chain of islands off the coast of the India. Genetically they are most closesly related to asians. particularly those on the indian subcontinent. but in terms of phenotype they look Africa. or more exactly, very close to the black african phenotype.
so are these people black? in terms of phenotype they definitely look black. and if you put them in modern american clothes and put them in the streets of NYC, they would get treated black. HOWEVER, genetically they are about as far from africans as you can get and they are geneticaly most closesly related to asians.
this is why we call race a social construct. there is no scientific basis for it. as humans we just use it as a shorthand to assign closeness in relation. it works most times. but like all non-scientific methods, its not foolproof. its simply another short-hand form of human behavior. just like all other forms of discrimination.