[packagingguy]

In high school biology it was taught that a species is defined by the ability of a male and a female to produce fertile offspring.

A donkey and a horse make a sterile mule. Therefore they are not the same species.

A Labrador retriever can mate with a bulldog, as different as they are, and still produce fertile offspring. Therefore they are of the same species.

If ancient Homo sapiens mated with other hominids and produced fertile offspring, which in the case of Neanderthals they did, should the two groups be considered subspecies, not separate species?

[JimRed]

If ancient Homo sapiens mated with other hominids and produced fertile offspring, which in the case of Neanderthals they did, should the two groups be considered subspecies, not separate species?

Looks that way, but I'll leave the determination to those who deem themselves scientists.

[evets]

A Labrador retriever can mate with a bullfrog

Nephilim - Genesis 6:4

[Bikkuri]

"make a sterile mule"

Interesting, I didn't know that.

[SunkenCiv]

Most people today carry known Neandertal DNA — and that’s based on the DNA isolated from just a few individuals. Most people carry as much or somewhat more Neandertal DNA as they do the DNA of each of 46 of their great-great-great-great-great-grandparents, who were obviously not nearly as long ago.

[gleeaikin]

A donkey and a horse have a different number of chromosomes. Therefore cannot yield live young. Tigers and lions have the same number of chromosomes, and have produced hybrids.