The English scientist Charles Darwin introduced the theory of evolution through natural selection with the publication of his book “On the Origin of Species” in 1859. This started a fierce argument among nineteenth-century scientists but the massive evidence coming from various other branches of science established evolution’s truth beyond a reasonable doubt before the twentieth century. Surprisingly though, more than 150 years after its introduction, it is still not uncommon to hear evolution is just a theory, implying that it is yet to be proven.
Is evolution just a theory? Do theories become facts only when they are proven?
A hypothesis is a suggested solution for an unexplained occurrence that does not fit into current accepted scientific theory. For a hypothesis to be termed a scientific hypothesis, it has to be falsifiable, and testifiable. It is also important to note that scientists do not test hypotheses with a pre-determined outcome in mind.
Following are examples for scientific hypotheses:
- Moisture levels in the air may affect bacterial growth.
- 80% of the U.S. population gets a divorce because of irreconcilable differences.
- Women taking vitamin E grow hair faster than those taking vitamin K.
- The Moon formed from the ejecta of a collision between the proto-Earth and a Mars-sized planetesimal, approximately 4.5 billion years ago.
Scientific Theories, and Scientific Facts
The word theory entered the English language in the late sixteenth century meaning conception, mental scheme, speculation. Arts and sciences began using the word in the seventeenth century but in a different meaning.
Contrary to popular belief, in science, a theory is not the best-educated guess scientists have about a certain natural phenomenon. On the contrary, a scientific theory is a well-confirmed type of explanation of nature, made in a way consistent with modern scientific methods.
A scientific theory is a framework for observations and facts in the natural world, and it does not only address existing scientific data but also makes predictions. Scientific theories are repeatedly tested confirmed through experiments or observation.
Following are some examples of scientific theories:
- Cell theory
- The Theory of Gravity
- General relativity
Following are some examples of scientific facts:
- The Eiffel Tower can be 15 cm taller during the summer
- Polar bears are nearly undetectable by infrared cameras
- The Earth is a giant magnet
The key difference between theories and facts is that theories may change, or the way that they are interpreted may change, but facts stay the same.
A scientific law is a statement describing what always happens under certain conditions, and it can often be expressed as mathematical equations.
- Newton’s laws of motion
- Archimedes’ Principle
- Laws of Thermodynamics
Finally, scientific theories do not graduate to become scientific laws.
Why Is Evolution Not Just A Theory
Evolution is the change in the heritable characteristics of biological populations over successive generations.
We know that evolution is a fact thanks to massive evidence from other branches of science such as paleontology, genetics, zoology, and molecular biology. The theory of evolution merely explains what the mechanics of evolution are, and how it works. The theory of evolution is, like most other scientific theories, a living theory. As our scientific knowledge improves so will the theory of evolution.