We have instincts that have served us well over the past few thousand years. We’re adaptable creatures, capable of evaluating situations, adjusting them or adjusting to them, or fleeing them. There must have been a cave-dwelling ancestor who opened one eye on a Thursday morning and began to evaluate the noise he could hear outside the entrance. Maybe these were his thoughts: “How big a stick was it that snapped? Can I hear it breathing? Was it something we sometimes eat, or that sometimes tries to eat us? Where’s that stone axe? I wonder if Dug over in 4A heard it? Maybe Dug is out early? Is everybody from our clan still inside? Durn fire burned down again. Did I bring firewood in last night? Where’s the spear? If it’s a saber tooth tiger, we’ll have to make a stand here where we’re protected on three sides. If it’s a hungry saber tooth tiger, we’ll run a goat out into the brush, then run like the wind to shelter with the folks over at the big camp on the river. If it’s nothing, I’ve got to work on a better supply of hatchets and rocks. Maybe I should think about just moving over to the river camp anyway.”