Now Erlandson, working with experts in bones, plants, and landscapes, wants to know how people lived on Santa Cruz before Europeans disrupted Chumash culture and laid waste to the environment. On this week’s expedition, Erlandson and Gill are gathering samples for dating prehistoric sites on the island’s western half. “We’ve recorded about 150 new sites,” Erlandson says the next morning, slipping his trowel inside his backpack. “And we’ve visited scores of others that already were surveyed.”