It's not an idle question because natural selection is supposed to lead to the creation of species but if we cannot find a good descriptive definition of species what has natural selection created?
It basically amounts to selection of individual genetic “units”. This is still hard to define because science has no way of knowing whether or not their were silent mutations or gene reversals in the extinct phylogenetic lines. That data is totally lost to time. The modern definitions (such as Ernst Mayr’s biological species concept) are better than the old ideas of population selection but they are not all-inclusive. It also doesn’t help that fossils and ancient DNA tend to be destroyed by the environment far more often than not.