Why Is Evolution Considered a Theory and a Fact?


Diego Sanchez

Evolution is a widely accepted scientific theory that explains how organisms have changed over time through natural selection. However, some people may argue that evolution is only a theory and not a fact. In this article, we will explore why evolution is considered both a theory and a fact.

What is Evolution?

Evolution is the process by which species of organisms change over time through natural selection. This means that certain traits or characteristics that allow an organism to survive and reproduce in its environment will become more common in the population over time.

For example, imagine two groups of birds living on different islands. One group has longer beaks than the other group because they evolved to eat insects that hide deep inside flowers.

Over time, the birds with longer beaks will be more successful at finding food and passing on their genes to the next generation. Eventually, the entire population of birds on that island may have longer beaks.

Why is Evolution Considered a Theory?

A scientific theory is an explanation of a natural phenomenon that has been extensively tested and supported by evidence from multiple sources. Evolution meets this definition because it has been studied for centuries by scientists from many different fields, including biology, genetics, geology, and paleontology.

Scientists have gathered abundant evidence supporting evolution over many years. For example:

  • Fossil records show how species have changed over time
  • Comparative anatomy shows similarities between species indicating common ancestry
  • Genetic evidence supports common ancestry between related species
  • Laboratory experiments show how organisms can evolve under different conditions

This overwhelming amount of evidence supports the theory of evolution as an explanation for how life on Earth has developed over billions of years.

Why is Evolution Considered a Fact?

In science, facts are observations that can be repeatedly confirmed through experimentation or observation. While evolution as a theory is based on a wide range of evidence, there are also specific facts that support the idea of evolution.

One such fact is the existence of vestigial structures. These are body parts that serve no apparent function in an organism but have been inherited from evolutionary ancestors. For example, whales have small pelvic bones that serve no purpose because their ancestors had legs and walked on land.

Another fact is the observation of speciation, which is the process by which new species arise from existing ones. Scientists have observed this happening in nature and it has also been replicated in laboratory experiments.


In conclusion, evolution is both a theory and a fact. The theory of evolution explains how organisms have changed over time through natural selection and has been extensively supported by scientific evidence from many different fields. Additionally, there are specific observations or facts that support the idea of evolution as well.

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