Human evolution and what fossils can tell us

In a nutshell

Evolution is how living things have changed over time and new species are formed. It's really important for scientists to collect evidence on how living things have changed so that we know how humans and other species came about.

Evolution

Definition

Evolution is how living things have slowly changed over time to form new species. Species are groups of organisms that can breed with each other to produce children who can also have children.

Many scientists have had ideas about evolution. Jean-Baptiste Lamarck believed that giraffes had developed longer necks as they stretched up to the trees. We now know that's not true!

Charles Darwin wrote a book in $1859$ called "The Origin of Species" where he introduced the idea of evolution. He explained that individuals within one species show small differences with each other - one individual might be stronger or faster.

The individuals who had characteristics that helped them survive the environment were more likely to have children and give these characteristics to them.

Eventually, the changes add up in a species to the point that they don't just become better adapted to their environment; they become a whole new species. This process underlying evolution is called natural selection.

Example

Peppered moths were originally a pale colour. These moths were often found on tree trunks but pollution from factories made the tree trunks darker which meant that it was easier for predators to see the pale peppered moths. Variation meant that some of the moths were darker. These ones survived as they were better camouflaged. Therefore, they produced offspring with the darker colour. Over time, the peppered moths became darker in colour.

Evidence of evolution

We can study the course of change or the evolution of animals using fossils. These are pieces of rock that are imprinted with the shape of living things from millions of years ago. They show us how animal and plants used to look.

When an animal dies, it decomposes. The skeleton takes longer to break down because it is hard and dense. The skeleton leaves grooves in the rock. Eventually, the skeleton also breaks down and is dissolved in seawater, so only the rock grooves are preserved.

Fossils are really important because they tell us how an animal or plant used to look. We can collect lots of fossils and track how they have changed over many years.

Note: The bones of an animal are not a fossil. Only the imprint it has left in the rock is a fossil.