Geneticists in Canada have finally succeeded in an experiment that lasted for 40 generations. Generations of fruit flies, I mean. The flies were kept in containers, and lights were repeatedly flashed on them. When the number of flashes was two or four, the container was given a shake.
At that point, if you're a creature that can count, you'd start hunkering down for a shake when you counted that the even-numbered flash was coming up. The flies didn't do this -- not until they had evolved to learn how, which took 40 generations.