The Denisovans were one of three branches of the same family tree (Human, Neanderthals and Denisovans), but categorized as a sub-species of Homo Sapiens. To put it simply, an earlier common ancestor of Humans, Neanderthals and Denisovans migrated out of Africa and evolved into the Denisovans. Later migrations out of Africa resulted in us. I've simplified it somewhat, but that's a basic version of what happened.
Were Denisovans human?
The Denisovans were one of three branches of the same family tree (Human, Neanderthals and Denisovans), but categorized as a sub-species of Homo Sapiens. To put it simply, an earlier common ancestor of Humans, Neanderthals and Denisovans migrated out of Africa and evolved into the Denisovans. Later migrations out of Africa resulted in us. I've simplified it somewhat, but that's a basic version of what happened.
Edit: a word or two here and there.