A few things struck me about the series. The reason some varieties of human survived, it says - us - was adaptability. Our lineage was a jack of all trades, rather than being superbly adjusted to just one particular niche.
In the final episode, the series argues that homo sapiens eventually outdid the Neanderthals and other closely related species because of our capacity for imagination. It was a close-run thing, too. The species almost died out 75-100,000 years ago. There were as few homo sapiens in the whole world then as there are orangutangs now. Only the most adaptable of an inherently adaptable lineage made it through that chokepoint.
There is one scene in which two humans bury an ostrich egg filled with water in the ground, on the off chance that they will be passing that way again and need the water. No other living thing has the foresight to imagine and plan.
In a way, that is the origin of our whole idea of wealth as well. It is a side-artifact of our motivation to plan ahead and have choices in the future. It is probably connected to contingent aids to survival.
Of course, squirrels do the same when they store nuts for the winter, and more systematically. But perhaps the difference is that is predictable behavior for predictable outcomes, and pure instinct. For us, it is more a store of adaptability and choice and material survival, because for four million years has been our distinctive specialization.
One other thing becomes very evident. The reason for the evolution of the massive human brain is not so much dealing with the external environment, but the human environment: such as reading people's intentions, motivations, propensity to cooperate and form alliances. We can cooperate, and also drive each other crazy with office politics.
The physical world is much simpler and predictable than the human social world, and needs less brainpower. Bacteria can move towards opportunities. Cats are extremely good at instantaneously calculating where to pounce. Even we are good at solving the quite complex mathematics of the trajectory of a ball thrown high in the air so we can catch it, without being aware of it. It is hardwired into our brains, even if we would struggle with the formal mechanics of ballistic trajectories.
Understanding people is the most difficult task the brain has. And that is why it evolved to be so large, despite the huge demands in terms of energy.
