Naming All the Animals — What is a “Species” Anyway?

Photo by Kevin Jackson on Unsplash

This post was triggered by an article that said that the Northwestern crow and the American crow are, well. Interbreeding so much that they are no longer separate species.

The fact is that “species” is a kind of arbitrary designation.

What is the Traditional Definition of Species?

A species is defined as the largest group that can interbreed and produce fertile offspring. Or the biggest gene pool under natural conditions.

The problem with this definition is that it just, plain, doesn’t work.

Birds, in particular, will quite cheerfully mate with related species, including in the wild, and produce healthy and fertile offspring. The same with canines — wolfdogs and coydogs are also healthy and fertile. In felines, male hybrids are infertile. but female ones are perfectly capable of breeding.

There have even been instances of female mules, the hybrid known for its sterility, producing offspring. In ancient Rome a “pregnant mule” was a euphemism for a possible, but highly unlikely event.

In other words, there are too many exceptions to “interbreed and produce fertile offspring” for it to be a meaningful definition. Instead, the working definition of species tends to be a…