>One point to note is that humans evolved from apes at a quick pace. I've heard claims that longer life-span, the ability to engage in complex vocalizations, opposable thumbs, upright stance, binocular vision and so-forth are all pretty recent innovation over evolutionary short period, with large brain size turning out to be last addition.

It is interesting how we evolved all these necessary things pretty quickly, though if we look at other apes, they generally also possess opposable thumbs and binocular vision. Sometimes I wonder if there was help, such as a large, black monolith...