There is generally a gradual change between regions, though, like between the Middle East and Europe you'll find people who look a bit like both, so it wouldn't be fair to just categorize them as one or the other because they're neither. We would just call them white or middle eastern, though, based on which they look more like or which region they came from.
If we were to check the genomes of each little group of people and decide race categories based on that, then we could say our categorization has a base in biology.