Science
What is evolution?
Quick answer
Evolution is the way living things change over many generations. Individuals with features that help them survive tend to have more young, so those features become more common over time.
In one sentence
Evolution is the slow change in living things over many, many generations, as features that help them survive become more common.
Explained
Look at a litter of puppies. They are all slightly different: one has longer legs, another thicker fur. Living things vary, and many of those differences are passed from parents to their young.
Now imagine a group of animals living somewhere cold. The ones with thicker fur stay warmer, so they are more likely to survive and have babies. Their babies tend to inherit thick fur. Over many generations, thick fur becomes common in that group. This process is called natural selection, and it is the main way evolution happens.
Charles Darwin explained this idea in his 1859 book On the Origin of Species. Alfred Russel Wallace worked out the same idea at the same time. Since then, evolution has become one of the best-supported ideas in science.
The evidence comes from several directions:
- Fossils show living things that existed long ago, many of them different from anything alive today.
- DNA shows that living things are related. The more alike their DNA, the more closely related they are.
- Living animals show change happening, such as bacteria evolving resistance to medicines.
For large animals, big changes usually take many thousands or millions of years. Life on Earth has been changing for more than 3.5 billion years, which gives plenty of time for small changes to add up.
Many families and faith communities also think about how life began in different ways. Science focuses on the evidence for how living things have changed over time.
Examples
- Finches on the Galápagos Islands have different beak shapes suited to different foods, such as cracking seeds or catching insects.
- Birds evolved from small feathered dinosaurs.
- Whales evolved from land mammals; whale skeletons still have tiny hip bones.
- Peppered moths in Britain became darker in sooty industrial areas, then paler again when the air got cleaner.
Common mistakes
- "Humans evolved from monkeys." Humans, chimpanzees and other apes share common ancestors. We are cousins, not descendants of today's apes.
- "Animals change on purpose." A giraffe cannot stretch its neck longer and pass it on. Variation happens first; the environment "selects" which features survive.
- "It's just a theory." In science, a theory is a well-tested explanation backed by lots of evidence, like the theory of gravity.
Quick quiz
Evolution
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Question 1 of 4
Who wrote On the Origin of Species in 1859?
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Related topics
Fossils
Fossils are the preserved remains or traces of plants and animals that lived long ago, usually found in sedimentary rock. They help scientists learn how life on Earth has changed.
Habitats
A habitat is the natural home of a living thing, where it finds the food, water, shelter and space it needs to survive.
Life cycles
A life cycle is the series of changes a living thing goes through from the start of its life to becoming an adult that can produce young, so the cycle begins again.
Living things
Living things are organisms that grow, feed, get rid of waste, sense the world and reproduce. Plants, animals, fungi and bacteria are all alive.
Cells
A cell is the smallest living unit. Every living thing is made of one or more cells, each with a membrane, cytoplasm and, in plants and animals, a nucleus that controls it.
Atoms
An atom is the tiny building block of all matter. It has a nucleus of protons and neutrons in the middle with electrons around it. The number of protons decides which element it is.