My son, Tom, going on 4, knows nothing of Nintendo yet, but he can tell a wildebeest from a buffalo, and knows to look for a climbable tree when one of the latter glowers at you from the brush. He can take or leave Legos, but he was in a joyous engineering frenzy when, on a dirt airstrip in Botswana, we built a corral of thorny acacia branches around our little twin-engine six-seat Beechcraft to keep hyenas from gnawing on the undercarriage.