If Homo sapiens and Neanderthals are different species, how did they interbreed and produce the fertile offspring needed for modern humans to have some Neanderthal DNA?

Question

I was told that two seperate species couldn’t interbreed and produce fertile offspring, so I don’t understand how we ended up with some Neanderthal DNA.

In: Biology

Answer 1

The Neanderthal are sometimes classified as *Homo neanderthalensis*, and as *Homo sapiens neanderthalensis* by others.

Fun fact:. ‘th’ in German is pronounced as a ‘t’, and the Neander valley changed it’s spelling to ‘Neandertal’ when the Germans changed all the ‘th’s to ‘t’s around 1900, but the hominids retained the old spelling. It’s still properly pronounced Neandertal, but mostly by anthropologists.

Anyway, species definition isn’t so cut and dried. It sometimes has more to do with whether two species *do* interbreed, more than whether they *can*. Some bird species can, but have different birdsongs, so they don’t. Sometimes it’s physical distance or population isolation. Sometimes by DNA. There’s no general agreement and no one definition fits all cases. Particularly for extinct species.