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

If a dog and a cat had a baby, would it be a cat? Would it be a dog? Or would it be a cog? Maybe a dat?

It definitely wouldn’t be one of the first two, so it’s a new species.

A 5 year old would be bored reading the paragraphs people have written below so I hope this helps