Bodhi:

Great to see you around again!  Wear it with pride.

Fmgd:

It's easy to come up with a hypothesis and tell a long, involved story to justify it -- especially at book length, when you can cherry-pick which evidence you present to your readers.  It's a lot harder to take all the evidence as it exists and figure out what story it tells.

JS

Bodhi:

It's not that I'm not hip to aquatic ape theory...it's that I don't see the evidence that it's true.  There's no evidence that Ardipithecus or any other transitional bipedal hominins were aquatic in any way, either in behavior or in diet -- and the fact that the transition to bipedalism preceded the increase in hominin brain size is evidence against it.

AAT is just one of many heterodox hypotheses that could be true...but given the evidence, they're far less parsimonious than the consensus narrative.

Vendramini's hypothesis correctly anticipated the current science (i.e. "mostly out of Africa, with a few percent admixture from male Neanderthals"), and I suspect he's at least partially correct.  However, the changes he posits take place 100-50 KYA, after humans had become anatomically modern and reached our maximum brain size, and therefore won't be covered in this series.

JS

Brynn:

Thank you!  It's a gift I do my best to share.

Vizeet:

General-purpose intelligence and breadth of diet usually go together.  If you're adapted to eat one single thing, it generally doesn't require intelligence to get it, just instinct -- whereas if you can eat just about anything, general-purpose intelligence helps you find and exploit it.  Example: ravens.

Asclepius:

The time of anatomically modern humans is vanishingly short by archaeological standards, perhaps 200,000 years so far.  The time of hominins is still very short, at perhaps six million years...and recall Part I, in which I compare the 65-million year reign of mammals to the 140 million year reign of dinosaurs. 

Given our ability to alter our environment and our current trajectory, we could very easily kill ourselves off in another few hundred years, leaving humans as the biological equivalent of a neutron bomb...200 KYA from inception to self-destruction would be essentially instantaneous when viewed from ten million years hence.

I'm glad your shirt arrived so quickly!  Usually overseas shipping takes longer...

Gayle:

The combination of Bergmann's rule and a cooling climate would imply that total body size might have increased during the Pliocene and Pleistocene, but I'm not aware of any data that shows brain size increasing.

JS

Peter:

Unfortunately, we have no direct evidence for when speech might have developed...so it's difficult to say when or where it might have been selected for!

JS