Introducing Homo prospectus

Imagine that it's a cold clear day in the dead of winter, and we're watching an early human as he emerges into the morning sun from a hut half-buried in drifted snow. In his hand is a spear with a tip he made last summer by flaking flint that he found high on a nearby hill. The spear is freshly mended, using twine braided during long winter nights, from dried grass kept in a pile in the hut.

To our surprise, he walks over to a tree and digs a large rock from the snow, which he carries with him as heads down a path beaten in the snow by frequent passing. We understand why he's lugging this heavy rock when we see his destination—a large, icebound lake. He walks fairly far out, then kneels down and methodically pounds with the rock, brushing away the chips of ice as he goes. His hands are protected from freezing by leather mittens, made in the fall by skinning a fox he'd caught in a snare, turning the fur side inward and stitching the halves together using sinew and an awl split from a coyote's jawbone. Once his hammering has broken through to clear water, he opens the hole by chipping away around its edges. From his sack, he takes a handful of beetles he captured months ago by smearing pine resin on a fallen tree trunk, letting the beetles dry in the sun before plucking them off.

That done, he begins his wait, standing as motionlessly as he can above the hole, his spear hoisted in a cocked arm. Before long, an unsuspecting fish has come to the surface to nibble at the tiny, dried beetles. Only the man's eyes move, carefully following the fish as it slowly circles in the hole. A practiced hunter, he knows that he is unlikely to have a second chance.

This matters. It is late in winter and he and his band are scrawny, like the dried grass that pokes desolately through the snow. Winter came early that year, and now calories and protein are scarce.

We are tempted to describe the miniscule movements of his eyes, which follow the fish, as "trained reflexes" or "automatic." After all, they are happening well below the level of conscious thought, and he is a very experienced hunter. Moreover, it is tempting to say that it is the function of the fisherman's perceptual system to tell him where the fish is, and the function of his memory to accurately represent similar past episodes, so that he will hit his mark by reproducing those motor patterns he executed in the past which were successful and thus reinforced.

Tempting, but this can't be right. Smooth eye movements are voluntary, not reflexive, automatic, or instinctual. They are effortful and even fatiguing. The eye is prone to wander, and it takes active concentration to keep focused on the gently moving fish. And his spear will not strike home if the fisherman knows only how he has thrown his spear in the past or where the fish is now. He needs to transform this past experience into something new, an anticipation of the likely motion of this particular fish at this particular moment, and a corresponding remapping of the motion he will make in tossing his spear. The spear must strike the fish just so, and the exact distance from his arm to the fish, the precise heft and balance of the mended spear in his hand, the toughness of this fish's skin are all things that he has never experienced in exactly this way. To reproduce a past successful throwing motion might yield no more than a glancing blow.

Even if he has hunted for years, he must still read and take into account the particular constellation of facts immediately before him.

Likewise, a skilled baseball batter might be facing a 3-2 count for the thousandth time, but the batter needs to anticipate what this pitcher will do at this point in this game. Hitting a small, spinning, speeding ball with a narrow bat at just the right angle, instant, and force is a highly exacting task, and no routine response or mere habit will do.

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