Know Thyself

The ones who got left behind. Making us the victors (?). This is the last essay episode in the Origins series, and covers the time frame from our last common ancestor with chimps up until the extinction of the Denisovans.  What's the foolproof way to identify a secret ape? Who was the singing-est biped of all? How much do large brains cost, and are they worth it? And why aren't those Neanderthals smiling?