Why Is the Theory of Evolution Considered a Theory and Not a Hypothesis?


Diego Sanchez

The theory of evolution is one of the most widely accepted scientific theories in the world today. It explains how all living organisms on this planet have evolved over time, adapting to their environment and changing to survive.

But why is it called a theory and not a hypothesis? Let’s explore this question further.

What is a hypothesis?

A hypothesis is a proposed explanation for an observed phenomenon. It is an educated guess that attempts to explain why something happens. Hypotheses are often based on limited evidence and are subject to testing and refinement through further research.

For example, a scientist might hypothesize that certain plants grow taller in response to increased sunlight. They would then conduct experiments to test this hypothesis by growing plants under varying levels of sunlight and measuring their growth.

What is a theory?

A theory, on the other hand, is a well-substantiated explanation for an observed phenomenon. It has been extensively tested and supported by multiple lines of evidence from various fields of study. A scientific theory can be thought of as the highest level of scientific understanding, representing our best current understanding of how something works.

Theories are constantly being refined as new evidence emerges or new technologies allow us to observe previously unknown phenomena. However, they are not simply guesses or hypotheses; they represent the consensus view of the scientific community based on extensive research and experimentation.

Why is evolution considered a theory?

Evolution is considered a theory because it meets all the criteria for being one. It has been extensively tested over many years by scientists from various fields, including biology, genetics, geology, paleontology, and more.

There are numerous lines of evidence that support evolution as a theory. Fossil records show gradual changes in species over time, with older fossils displaying simpler structures than newer ones. DNA analysis has also revealed similarities between different species that suggest common ancestry.

Other fields have also contributed to our understanding of evolution. For example, geology has shown that the Earth is much older than previously thought, providing more time for evolution to occur. Biogeography has shown patterns in the distribution of species that are consistent with evolution.


In conclusion, the theory of evolution is called a theory because it meets all the criteria for being one. It is a well-supported explanation for how all living organisms on this planet have evolved over time through natural selection and adaptation. While there may be some ongoing debates and refinements to our understanding of evolution, it remains one of the most robustly supported scientific theories in existence today.