When Charles Darwin came up with the theory of evolution, he imagined the process took place slowly, across many thousands of years.
Research, however, suggests that when environmental change is substantial and persistent, evolution can be quite rapid. In just half a century, the Atlantic killifish evolved to survive in waters with lethally high pollution levels.
Contemporary evolution, as it is known, occurs readily in animals with short generation times – such mutations can be selected for and passed down the generations quickly.
Suppose a mutation cropped up that gave flies the dexterity to manipulate window catches, or the wing power to fly through a down- draft and buzz off back into the outside world. If this mutation also made the fly more likely to survive and reproduce, there is no reason why it couldn’t spread speedily through the population.
