Costly Smarts
Using selective breeding, researchers can make rats, bees and flies a lot better at learning. Animals that are better learners should over time come to dominate a population. Yet improved learning ability does not get selected amongst these animals in the wild. Tadeusz Kawecki may have discovered why.
Kawecki gave flies two different fruits as egg laying sites. One of these was laced with a bitter additive that could be detected only on contact. The flies were then given the same fruit but without an additive. Flies that avoided the fruit which had been bitter were deemed to have learned from their experience. Their offspring were reared and the experiment was run again.
After repeating the experiment for 30 generations, the offspring of the learned flies were compared with normal flies. Learning ability was bred into the flies, but it shortened their lives by 15%. And when flies were bread to live abnormally long lives, they learned less well than even average flies.