In the quest to understand the evolution of intelligence, one of the most tantalizing questions is this: when did prehistoric man become man as we know it, with abstract thought, complex language, and self-awareness?

Obviously, we can't directly test the cognition of prehistoric man, but clues and artifacts left behind help us reconstruct a picture of their cognitive capacity. At least 9,000 years ago, humans were building drive lanes for caribou hunts, with corridors, blinds, and cul-de-sacs formed from stone. Other artifacts found at the site indicate that the humans adopted different strategies based on season, changing the size of their hunting party. These complex strategies and constructions were necessary; early North American humans were absolutely dependent on herds of caribou and other animals, and being able to understand (and channel) their movements removed the deadly element of uncertainty.

The evolutionary pressure to minimize uncertainty (coupled with the massive processing demands of large, complex social groups) likely facilitated the runaway evolution of intelligence in humans. By the way, 9,000 years is a blink of an eye on evolutionary timescales; it is likely that the humans who built these channels were practically indistinguishable from you and me!