There's a new episode of PBS Eons.  Paranthropus robustus and related species lived and evolved along side of us around 1 – 2 million years ago.  What happened to them?

There was a group of hominins, those creatures more closely related to us than to chimpanzees, that did take a different, parallel journey from our ancestors. Our paths ran beside each other – and potentially even crossed at times – but while ours led us here, theirs led to extinction."