[piasa]

If they can interbreed and produce viable fertile offspring, they’re not a different species. They’re human.

[x]

If they can interbreed and produce viable fertile offspring, they’re not a different species. They’re human.

Now they are. Or they will be.

But when we thought they were different species we thought they couldn't interbreed.

The Internet is telling me that dogs and wolves are now considered the same species because they can interbreed to produce hybrids that can also interbreed.

First I've heard of it.

[Jack Black]

If they can interbreed and produce viable fertile offspring, they’re not a different species. They’re human.

A decent rule of thumb, but it's more complicated than that according to the wikipedia article on species. It sort of like the famous Supreme Court Justice's definition of porno: I know it when I see it.

[tumblindice]

You are correct. That is the definition of ‘species’: the ability to interbreed.