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Life on Earth shows remarkable diversity. Multiple lines of research provide strong evidence that evolution produced this diversity.

Some evidence comes from direct observation. Scientists can observe the evolution of antibiotic resistance in bacteria.

Because bacteria multiply rapidly, random mutations appear frequently. Some of these mutations allow certain bacteria to survive exposure to antibiotics. Over time, bacteria with mutations that confer antibiotic resistance have a survival advantage.

Developmental biology also provides evidence for evolution. Early vertebrate embryos share similar structures, such as pharyngeal arches and a post-anal tail. These shared features reflect common ancestry. As development continues, embryos gradually develop traits that define their species.

Comparative anatomy also supports evolution. For example, birds, humans, and whales share a common ancestor. This relationship is reflected in their similar forelimb bone structures, even though these limbs perform different functions today.

The fossil record gives another important line of evidence. Fossils show that many species lived in the past but are now extinct.

Scientists can sometimes date fossils directly. They can also estimate fossil ages by studying the surrounding sedimentary rock layers. Some fossils show transitional features between major groups, providing direct evidence of intermediate forms and gradual change over time.

Evolution can also be studied at the molecular level. All living organisms use DNA to store and transmit genetic information.

By comparing DNA sequences, scientists can see how closely species are related. Species with more similar DNA sequences share a more recent common ancestor.

Biogeography also supports evolution. This field studies how organisms are distributed across the planet.

A well-known example comes from the Galápagos finches. Different food sources favored different beak shapes. Over many generations, these differences led to divergence between populations, contributing to the formation of new species.

Together, evidence from observation, development, anatomy, fossils, genetics, and biogeography shows that evolution explains the diversity of life on Earth.

As evolutionary biologist Theodosius Dobzhansky wrote, “Nothing in biology makes sense except in the light of evolution.”