THE EXPLAINER

HOW DOES EVOLUTION WORK?

WHAT EXACTLY IS EVOLUTION?

Plant and animal species come in a huge variety of shapes and sizes. The consensus is that all of these life forms – from alligators to zebras, hawthorn trees to humans – ultimately arose from the same microscopic ancestor that lived about 3.5 to 4 billion years ago. Evolution explains how. It is the process through which populations of living things can physically change through time by picking up new inherited characteristics.

HOW DO WE KNOW THAT HUMANS EVOLVED FROM APES?

The evolutionary changes we see occurring over a few decades are modest: a cricket that evolves to be silent is still a cricket. When evolution unfolds over longer timescales – thousands or millions of years – it can lead to much larger changes in physical appearance. This is why a microbe that lived billions of years ago ultimately evolved into every species alive today.

By carefully assessing physical and genetic similarities, evolutionary biologists can work out which species belong in the same area of the family tree of life. Doing so suggests that humans are more closely related to chimpanzees than to any other species alive today, implying that we both evolved from the same ‘parent’ species, thought to have lived around 7 to 13 million years ago. Just last year, researchers announced that they had found fossils of an 11.6-million-year-old tree-dwelling ape, which they named Danuvius guggenmosi. It had adaptations for walking upright on two legs like we do, but its arms were more suited to hanging from branches, like chimpanzees. This mix of features supports the idea that humans and chimps have a common ancestor, and adds to the abundant fossil evidence that humans really did evolve from (and technically still are) apes.