I'm kneeling on a sandy beach in Costa Rica on a balmy January night helping biologists administer an ultrasound to a leatherback sea turtle. They are hoping to learn more about her reproductive cycle, to better protect populations of this endangered reptile at its nesting beaches around the world. The turtle has come ashore to lay her eggs, as her kind have done since dinosaurs roamed the earth. I watched as she hauled her enormous bulk up the beach, pivoted slowly around to face the ocean, and began scooping out an oval pit in the sand with her hind flippers. She soon entered her egg-laying trance, a quiescent state in which she remains for an hour until she covers over her nest and heads back to the surf.

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