Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [16]
Doing these experiments requires painstaking maintenance of the tiny flies in hundreds of jars held under exactly identical conditions—the same temperature, the same food, and in complete darkness. Most modern biology buildings have elaborate facilities for keeping the insects, but of course many scientists labor in less-than-ideal circumstances. As it happened, Kawecki used to work at the University of Basel, also in Switzerland, where his lab was in a crumbling fifteenth-century building in which the doctoral students used a former lecture hall of Friedrich Nietzsche for their office. Although charmingly located on the banks of the Rhine River and architecturally impressive, the building suffered from a variety of maintenance ills, many of which required the service people to enter the attic. The attic in turn was occupied by numerous pigeons and swifts, and one of the building maintenance workers complained so vociferously about the birds' lice and fleas he supposedly encountered in his effort to repair things that an exterminator was called in. While most people welcome the removal of insects from their homes, in a building where precious experimental flies are being kept, the situation is somewhat different. Kawecki and his colleagues made numerous panicky phone calls to the exterminators to make sure the process wouldn't decimate their subjects, and were assured that all would be well.
Unfortunately, as Kawecki puts it, "the only animals [the exterminator] knew about were cats and budgerigars," and the insecticide proved fatal to some of the carefully reared fruit flies. Luckily, the scientists had to stagger the breeding of the flies because they didn't have enough room to raise them all at once, so they did not lose all of their years of effort. But Kawecki remains nettled at the company, which never admitted any wrongdoing, instead suggesting "it was our fault, keeping those stupid flies rather than cats and budgerigars, as proper Swiss citizens do."
Despite these setbacks, one generation of flies led to another. Through the selective breeding process, the flies rapidly improved their ability to remember which substance was attractive and which was not, and after about twenty generations, Kawecki had flies that could go to the bug equivalent of Harvard or Princeton. Instead of taking three hours to learn which substance has quinine in it, the new and improved flies knocked the task out in less than an hour. What's more, they could generalize their ability to other tasks that required them to avoid or prefer one odor to another, and even to other stimuli besides odor, which means that the flies were not simply evolving better discrimination of pineapple versus orange, they were actually getting smarter.
Presumably, being able to detect good places to feed and lay eggs faster would also be useful in the real world, outside Kawecki's lab. So why don't flies show this brainiac capacity naturally? To put it another way, if the flies can get to be so smart, why aren't they rich, or at least more successful?
The answer seems to be that they don't live long enough. The life span of flies from the smarter lines averaged 15 percent shorter than their unselected relatives. Furthermore, the smarter females laid fewer eggs, an ominous characteristic from the standpoint of evolution, since it means fewer potential copies of genes in future generations. The decreased survival was particularly notable when food was in short supply, which gives a clue to the reason for the finding: learning is costly, and investing brain resources into intelligence may mean that you pay the price somewhere else. More brain, fewer eggs. The trade-off even occurs within the lifetime of a single fly. A group of flies that was trained to associate an odor with a mechanical shock and then deprived of