But the chill… or something else… brought a sudden shift in mood. Marcella’s hair stood up on the back of her neck and her heart beat faster. She clutched at her silver squash-blossom necklace.

What brought that on? she wondered, squinting and looking out into the darkness through the open window. She saw nothing but the silhouettes of trees moving in the wind, and heard no sound but the rustling leaves, wind chimes, and distant road noise.

It was a Lewis moment.

Lewis was a cognitive archaeologist in Arizona, a colleague and intellectual sparring partner. He had a keen interest in how Paleo-Indians managed to survive among lightning-fast sabertoothed tigers and other giant predators of stealth and speed. His research into the functioning of the human brain led to the interesting discovery that the subconscious can perceive a movement or a threat and the body can respond several seconds before the conscious mind even becomes aware. A nice little brain function that helped early humans survive at a time when animals were bigger, faster, and had way sharper teeth.

Marcella agreed with this idea because she had experienced the phenomenon firsthand. It happened while she was walking through an overgrown field surveying for signs of prehistoric inhabitants-looking for arrowheads, actually. She found herself suddenly breathing rapidly, her heart pounding… and inexplicably she was standing more than three feet to the side of where she had been a moment before. She had no idea what had happened or why she had jumped to the side. But her eyes were fixed on the spot where her next step would have been. There, hidden in the grass, lay a rattlesnake. Subconscious awareness and involuntary response had kicked in. A prehistoric survival function had saved her from harm.