Humans we interacted with.

Neanderthals, named after the region in Germany where they were first discovered, are our closest ancestor. However a lot of new evidence has come out recently that makes many experts consider them the same species as us. The SciShow lays out the evidence.

Neanderthals weren't the only human ancestor we shared the earth (and our DNA) with. The mysterious Denisovans also contribute a portion of their genome to us.