system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 the known different human species? I feel like a literal idiot for not knowing there have been different species of humans in the past.
gpt
There are 6 well established different species that once shared our genus. All were upright walking, likely communicating, tool using, well, humans. Though they were substantially different from Sapiens.

Homo Habilis was the first, living from about 2.5 million years ago until about 1.5 million years ago. They probably looked more like other great apes (not walking quite as upright as the rest of the genus for example) but definitely used stone tools, which earned them their name (which means handy man).

Homo Erectus (upright man) looked a lot more like Sapiens than Habilis. They lived in Africa and the Middle East and were around from about 1.9 million years ago until about 70,000-40,000 years ago, totally coincidentally the time when Sapiens were expanding across the globe.

Homo Heidelbergensis is another species that lived about 600,000 to about 200,000 years ago. They had larger brains than Erectus but were otherwise highly similar and some people think they weren't distinct species (they also lived in the same regions). 

Homo Floresiensis are a species that likely got to and then bred seperately from another species in the genus leading them to become a separate species. They are a great example of island dwarfism (species that evolve on relatively small islands tend to become smaller than continental counterparts). They were around 3.5 feet tall. They lived from about maybe (they were discovered relatively recently, so we're not too sure) 200,000 years ago until about 12,000 years ago...again, this likely has nothing to do with the fact that Sapiens was likely colonizing southeast Asia at the time.

Neanderthals lived in most of Europe the middle east, and central Asia, splitting off and migrating away from the African cousins somewhere around 600,000 years ago before...::cough::...mysteriously going extinct just as Sapiens were spreading out of Africa into those regions around 40,000 years ago. They were generally larger and had larger brains than modern humans.

Then there's us. What we likely had going for us was the ability to cooperate in large groups. Evidence suggests that groups of other human species rarely were larger than a few dozen while Sapiens learned how to communicate and cooperate in larger and more complex groups.