Another way to test hypotheses about adaptation is to consider trait variation across a group of species instead of focusing on the trait of a single species. Rather than seeking to explain why polar bears have fur of a certain thickness, one tries to explain why bears in colder climates have thicker fur than bears in warmer climates. The former problem is hard to solve, since it is hard to say exactly what fur thickness polar bears should have if natural selection guided the evolution of that trait.

If the organisms in a species now have trait T, and this trait now helps those organisms to survive and reproduce because the trait has effect E, a natural hypothesis to consider is that T evolved in the lineage leading to those current organisms because T had effect E. This hypothesis is "natural," but it often isn't true!

The racial categories that are used in a given society (for example, in contemporary America) are biologically meaningless, but sometimes it turns out that a vernacular racial category has biological reality.

Unfortunately, philosophers of science usually regard scientific realism and scientific anti-realism as monistic doctrines. The assumption is that there is one goal of all scientific inference - finding propositions that are true, or finding propositions that are predictively accurate. In fact, there are multiple goals. Sometimes realism is the right interpretation of a scientific problem, while at other times instrumentalism is.

Instead of thinking of the question of race genealogically, and leaving it open whether vernacular races are genealogical units, the interest in biomedicine has been to determine whether vernacular racial categories are medically useful in diagnosis and treatment. There is on-going debate about this.

I disagree with the widely held view that it is metaphysical necessity, not nomological, that matters in the mind/body problem.

Creationists have long held that evolutionary theory is atheistic; defenders of the theory do the theory no favor when they agree.