One hundred and seventy-four years ago, Charles Darwin first set foot on the Galapagos Islands aboard the Beagle. Since then, the islands and the unique species they house have been a source of inspiration for many an evolutionary biologist. Even so, it is gratifying to see that even now, on the bicentennial of Darwin's birth, the Galapagos have not yet finished yielding their secrets.
During Darwin's five-week stint on the Galapagos, he observed two types of iguana. One was a marine version that, uniquely for lizards, swam and fed in the ocean, and the other was a cactus-eating landlubber…