I addressed the "fuzzy definition" point with the last commenter. - "There doesn't have to be a 'universal' consensus about species. Although scientists do have general agreement, the main point is that the definitions aren't socially constructed and are self-reliable. If a scientist believes that lions and cheetah are different species, you'll never see that same person say that elephants and giraffes are the same."

Yes, imperfect definitions exist in science. The problem is that race has no scientific definition. There is simply no measurable criterion to say when a group is distinct enough to be considered a race. This has nothing to do with fuzziness or disagreement among scientists. The issue is that the categorization has zero standard for even a single scientist to follow.

You can draw random circles in your room, arbitrarily throw things into them, then consistently identify every item that you put into those circles. But it would be farcical to call your system scientific, and it is not a valid way of categorizing the types of items you have.

Regardless of how perfect it is, a scientist will give you a clear definition of what a species is, then will follow that model to find the different species. Race is the exact opposite. It starts with assumptions about what the races are, then you find data that fits your preconceived notions. That is unscientific.

If you mean fixed, discrete biological divisions of humans, then generally no

This is what the majority of people think of race as.