system
Given the following post, respond as if you're commenting on Reddit:
human
Why is there only one species of Human?

According to Wikipedia, humans exited Africa roughly 100,000 years ago, so we've been spread out across continents for quite a long time. If there was so much geographic separation between populations for such a long time, why didn't different species (or subspecies) of humans develop? Why are we the only ones left?

It just seems crazy that I'm the same species as every other person on earth, even though we might share a common ancestor tens of thousands of years ago. If there had been a bottleneck, where only a small population of humans survived and then populated the world, then I could understand it more. But it seems incredible that there's so many types of tiger, lion, squirrel, etc. but only one intelligent primate.

I know there were other (sub)species such as homo erectus or neanderthals. But why did they all die out? Wasn't there enough room for pockets of them to survive somewhere? Why hasn't homo sapiens similarly fragmented into subspecies since then?
gpt
Modern humans have been around for a very short period of time. There are differences in race, asian people tend to be smaller, stuff like that. The problem is different races marry and those genes mix. If Asians only married pure blood Asians, Africans only married and procreated with other Africans thanks in hundreds of thousands of years different sub species would most likely start to occur. Seeing as how human population is all connected today, that won't happen.