[jlogajan]

From an evolutionary point of view, ability or inability to breed obviously has effects, so it is a good species differentiator. If you can interbreed, you are considered in the same species.

But what if you can interbreed, but don't want to. What if most neanderthals were unappealing to spaiens sapiens? Techically, even if they could interbreed, they didn't. So the evolutionary results are the same as IF they were different species.

In that case, I think it is actually safe to classify them as seperate species.

[Interesting Times]

But what if you can interbreed, but don't want to.

Unlikely. Humans have attempted to mate with members of the same sex, the opposite sex, cows, sheep, footwear and watermelons.

If there were Neanderthals around, the chance that some enterprising Homo Sapiens didn't give them a try is just about zilch.

[steve50]

If you ever left a bar at closing time you would realize that there is no such thing as "unappealing female" to a homo sapien male.

[sheik yerbouty]

Actually Neanderthal's "disappeared" as a result of the development of good cutting tools. Massive strength was no longer required, and non Neanderthal traits could then be passed down without catastrophic consequences.

[Physicist]

If you can interbreed, you are considered in the same species.

Just this morning I read a claim in Arctic Dreams by Barry Lopez (highly recommended!) that polar bears and brown bears can in some cases produce viable offspring.

As for Neanderthals, the genetics suggest that they were separate species. Until the mitochondrial DNA data came in, they always were considered two varieties of homo sapiens. I don't see how comparative anatomy can trump that.

[SevenDaysInMay]

Although totally un-PC, todays "race" is but biology's "sub-species". Differentiating race/location definitional parameters and infrequent cross-breeding between/among races/sub-species is often all biologists need to name a "new" sub-species.

I suspect that during the ebbs and flows of 7(?) ice sheets since Raquel Welch's One Million Years B.C., early tribes were forced out and likely back into Europe, perfecting the human warrior genes and social organizations during these many migrations. Breeding then as now was probably for alliance, wealth, and dominance, as it is now. Maybe Neanderthals were the original blonds.

What has love got to do with it?

[CholeraJoe]

If you can interbreed, you are considered in the same species.

Bison and domestic cattle can interbreed yet are not in the same species. Timberwolves and domestic dogs can interbreed - different species. Drake mallard ducks will attempt to breed with any female duck of any species - often successfully.

[Fury]

The real determining factor is can they bring the resultant fetus to term? Sheep and goats, although distinct species, can successfully breed, with there being fertilization and development of an embryo, but the embryo will not survive.

[Oberon]

But what if you can interbreed, but don't want to. What if most neanderthals were unappealing to spaiens sapiens? Techically, even if they could interbreed, they didn't. So the evolutionary results are the same as IF they were different species

Hmm. Interesting hypothesis. Would this have been before the invention of brewing?

[garbanzo]

Typically any separation either by "choice" or geographical dislocation usually results in speciation. It's genetical isolation which tends to result in reproductive differences.