system
Given the following post, respond as if you're commenting on Reddit:
human
Why are Neanderthals considered a different species from humans if we could interbreed and produce fertile offspring?

I've often heard the word species defined as the largest group of organisms that can interbreed and produce fertile offspring, if that is the case why do we consider Neanderthals a different species when many people today have Neanderthal ancestry?
gpt
species are more about having a distinct gene pool with little or no outside interbreeding, and neanderthals had that for a long time and so developed a genetic distinction of their own, becoming a separate species.

basically they are a different species because they formed a isolated group that didn't interbreed extensively for a long time and therefor evolved differently from other humanoids. the fact we could still interbreed is irrelevant to them being a separate species or not.

the thing is, the term species isn't as clear cut as most people believe. what exactly the crossover point between being a separate species and not being one isn't based on clear easily identified criteria.