Concept preview

What you will be able to do

1. 01List the main lines of evidence for evolution and explain how they fit together.
2. 02Distinguish homologous, analogous and vestigial structures and what each reveals about ancestry.
3. 03Explain how fossils, embryology and biogeography support descent with modification.
4. 04Describe how DNA and directly observed cases such as antibiotic resistance and the peppered moth provide evidence for evolution.

Before weighing the evidence it helps to be clear about what the theory of evolution actually claims: that all the species alive today are descended, with change, from earlier species, and ultimately from a single common ancestor that lived billions of years ago. This is often summarised as descent with modification. A common misunderstanding is that in science a theory is a mere guess; in fact a scientific theory is a well-tested explanation supported by many independent lines of evidence. Evolution is one of the best-supported ideas in all of science precisely because so many different fields — palaeontology, comparative anatomy, embryology, biogeography and molecular biology — point independently to the very same conclusion. When separate lines of evidence that could easily have disagreed instead agree, scientists become extremely confident that the explanation is correct.