eli5 If it’s suspected that early humans interbred with other species of humans, why would they be considered different species since the offspring were obviously fertile?

Question

eli5 If it’s suspected that early humans interbred with other species of humans, why would they be considered different species since the offspring were obviously fertile?

In: 54

Answer 1

The line between what is a different species or not is sort of arbitrary and not clearly defined. You get a lot of gray areas, such as where animals are clearly distinct genetically and physically and can still interbreed, and others where they’re superficially and genetically similar but can’t.