According to taxonomic classification, a is a group of organisms that can reproduce together and produce fertile offspring.
A subspecies is a further classification, but members of different subspecies can reproduce viably. There are two subspecies known, homo sapiens sapiens and homo sapiens idaltu. Some have suggested that Neanderthals were a subspecies of Homo sapiens as well.
Why aren't races classified biologically by subspecies?
I mean, blacks have very dissimilar appearences to whites and Asians or Indians.
You can denote several different physical features in different races other than skin color.
Blacks have dark skin, flat noses, big dicks etc.
Asians have tiny penises, light skin, slanted eyes, you get the picture.
I don't believe it's all cultural, there has to be some genetics involved.