Mark of Cain: One Homo to Rule Them All
There are a lot of species of the Panthera (lions, tigers, panthers, etc.) genus still around. Ditto for dogs. Not so Homo. We call ourselves Homo sapiens (wise man), but our late brother species might refer to us a bit more disparagingly. One hundred thousand years ago, there were at least six human species still extant, including Neandertals, Denisovans, Homo erectus, Homo ergaster, and the hobbit people of the Isla de Flores. And of course, us, the wise guys. Quite likely, there were others, as yet unknown, or perhaps, never to be known.
It seems that we are not exactly innocent in the demise of our late bretheren. Such, at least, is the message Yuval Noah Harari, a prof at the Hebrew University of Jerusalem and the teacher of Coursera's A Brief History of Humankind
It's early in the course, but it seems that he's not that impressed with our own prospects either. Compared to erectus, who managed 1.4 million years on the planet, we only have 200 k years in, and he thinks we might be lucky to make another thou.