How adaptation works

Fossils help scientists learn about adaptation

Adaptation is caused by evolution. Evolution is a process of gradual change, which makes animals more suited to survive in their surroundings. As they change, new species are formed. Scientists now think that all animals and plants on Earth today evolved from primitive creatures that lived hundreds of millions of years ago.

Bird beginnings

Scientists’ first evidence for evolution came from fossils. One of the most amazing was of a primitive bird-like creature, called Archaeopteryx, which lived at least 150 million years ago. It had feathers and wings, like today’s birds, but it also had tail-bones and teeth like a reptile. Scientists now think that birds evolved from dinosaurs, and that Archaeopteryx shows the link between them.

Powering evolution

Evolution works through a process called natural selection. An animal's young are always slightly different from one another, and some are more suited to their environment than the others. The survivors have a certain advantage over the others (such as a longer beak that can reach deeper into a flower), which they pass on to their own young. Gradually, over many generations, all individuals have it. A new species has formed – with a new adaptation.

The Earth’s environment is continually changing, posing new problems for living things, and individual animals within a species are always slightly different. This means that natural selection never stops. New species with new adaptations continue to evolve.

Evolving together or apart

Things aren’t always what they seem. Some species that look very similar have evolved from completely different backgrounds. For instance, scientists used to think that the ‘new world’ vultures of the Americas (such as the condor) belonged to the same family as the ‘old world’ vultures of Africa and Asia (such as the griffon vulture). They have similar broad wings, naked heads and both eat dead creatures. But we now know that they are not related. In fact, new world vultures are closer to storks. Both families have evolved the same adaptations for the same reasons in different parts of the world. This is called convergent evolution.

On the other hand, some closely related birds look very different. The tiny storm petrel, which flutters over the sea like a house martin, looks nothing like the mighty albatross. But the structure of its bill shows that it belongs to the same family. Evolution has taken these birds in different directions, by producing different adaptations for life at sea. This is called divergent evolution.