Similarly, the definition of species as individuals that breed with each other has importance for transmission of genes. By this rationale, transitive gene transmission makes ring species a "species".
A biologist told me that species are defined, not by theoretical interbreeding, but by actual breeding...so that a single species divided somehow in different environments, is now two species, even when no genetic change has occurred.
By this strange extrinsic definition, the human races were different species before global travel... and now are one.
And that SV hackers who only breed with other SV hackers, are a different species (and the rise in autistism incidence evidences a genetic effect - in a few million years, interbreeding will be impossible!). Similar for classes, the 1% etc.Though there is crossbreeding in practice, so at most these are ring species.
Species and race are vague terms we use for convenience. That's all. I think keeping them vaguely defined is a feature not a bug, because it could help prevent people assigning too much weight or meaning to them. If people get the idea that race and species can be precisely defined, then maybe they can be measured? Maybe we can use that to derive tests or policies? But trying to precisely define race and species is futile, like trying to put light in a box. I'd rather knowingly and consciously keep the ambiguity, to remind myself that the terminology isn't the reality.
[1] https://en.wikipedia.org/wiki/Ring_species