When Charles Darwin first stepped off the HMS Beagle and into the harsh and formidable world of the Gal pagos islands with their sun-baked lava, spiny cactus, and tangled brushwood, he encountered many birds and animals new to him. He marveled at the remarkable tameness of the birds and the striking dominance of reptiles in these islands, which made the archipelago seem like a journey back in time. On the shoreline were swarms of "hideous-looking"...