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Read an extended version of this article, and many more evolution myths, in our online special

Cosmologists make precise predictions about what will happen to the universe in 20 billion years time. Biologists struggle to predict how a few bacteria in a dish might evolve over 20 hours. Some claim that this lack of precise predictive power means evolution is not scientific.

However, what matters in science is not how much you can predict on the basis of a theory or how precise those predictions are, but whether you can make predictions that turn out to be right. Meteorologists don’t reject chaos theory because it tells them it is impossible to predict the weather 100 per cent accurately – on the contrary, they accept it because weather follows the broad patterns predicted by chaos theory.

The difficulty in predicting the path of evolution partly springs from organisms’ freedom to evolve in quite different directions. If we could wind the clock back 4 billion years and let life evolve all over again, its course might well be different. Life on this planet has also been shaped by chance events. If an asteroid had not wiped out the dinosaurs, intelligent life might have been very different, if it evolved at all.

Nevertheless, although evolution’s predictive power might appear limited, the theory can and is used to make all sorts of predictions. For a start, Darwin predicted that transitional fossils would be discovered, and millions – trillions if you count microfossils – have been uncovered. What’s more, researchers have predicted in which kinds of rocks and from what eras certain transitional fossils should turn up in, then gone out and found them, as with the half-fish, half-amphibian Tiktaalik.

Or take the famous peppered moth, which evolved black colouring to adapt to pollution-stained trees when industrialisation took place. Remove the pollution and, evolutionary theory predicts, the light strain should once again predominate – which is just what is happening.

This predictive power can also be put to much more practical use. For instance, evolutionary theory predicts that if you genetically engineer crops to produce a pesticide, this will lead to the evolution of insect strains which resist that pesticide, but it also predicts that you can slow the spread of resistance genes by growing regular plants alongside the GM ones. That has proved to be the case. Now, many researchers developing treatments for infectious diseases try to predict how resistance might evolve and to find ways to prevent this from happening, such as prescribing certain drugs in combination. This slows the evolution of resistance because pathogens have to acquire several different mutations to survive the treatment.

Read an extended version of this article, and many more evolution myths, in our online special