We do a pretty good job at appreciating the visible intricacies of nature: the antennae and legs and claws of a lobster, the geometrical order of the spots on a butterfly's wings. But a lot of nature's intricacies are hidden away inside single-celled creatures, such as the baker's yeast that makes bread rise and beer ferment. At an audition for a David Attenborough documentary, a yeast cell guzzling away on sugar is bound to do a lousy job. ("Thanks, don't call us; we'll call you. Send in the King Cobra!") But the intricacy of its metabolism is no less impressive. What's more, scientists know how to manipulate yeast in ways they can't with animals, and that power lets them set up experiments that yield clues to how that intricacy evolved.
The latest study of yeast's intricacy comes from the University of Wisconsin lab of Sean Carroll. Carroll has become the public's go-to guy for evo-devo, or the evolution of development, thanks to his book Endless Forms Most Beautiful. Carroll and his colleagues have carried out path-breaking experiments that reveal how relatively small changes in DNA can lead to dramatic changes in how animals grow into adults. A key point of Carroll's work, as well as that of many other evo-devo researchers, is that evolution is not just about the mutations that alter the way proteins work. The genes that encode those proteins are controlled by intricate switches, which determine where and when they make proteins. Change those switches, and you can change how an animal develops. For example, there's a circuit of genes that specifies the coordinates of a insect's overall body plan. Carroll and his colleagues have demonstrated that this same mapping system was borrowed to determine where spots go on butterfly wings.
