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 at the time 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 future predictions. Hence, scientific theories are repeatedly tested and confirmed through experiments or observation.
Following are some examples of scientific theories:
- Cell theory
- The Theory of Gravity
- The General Theory of Relativity
- Evolutionary Theory
Change in the heritable characteristics of biological populations over successive generations is called evolution.
We know that evolution is a fact thanks to massive evidence from other branches of science such as paleontology, genetics, zoology, and molecular biology. Evolutionary theory merely explains what the mechanics of evolution are, and how it works.
Following are some examples of observable evolution:
- Two distinct species of mice are mating, and their hybrid mice pups are immune to pesticides.
- Humans create specific dog breeds.
- Since its discovery, bacteria have increasingly evolved to outsmart antibiotics.
- A special fish managed to beat the toxic pollution in New York Cityís dirtiest river.
Darwin’s Evolutionary Theory
Discovered in the mid-nineteenth century by the English scientist Charles Darwin, evolutionary theory is based on the idea that all life on earth is related and gradually changes over time. The theory primarily explains the ongoing speciation of life since its emergence on Earth.
Charles Darwin introduced the theory of evolution through natural selection with the publication of his book “On the Origin of Species” in 1859. With this, Darwin started a fierce argument among his peers but the massive evidence coming from various other branches of science has established evolution’s truth beyond a reasonable doubt before the twentieth century.
Darwin’s theory of evolution is based on key facts and the inferences drawn from the populations of species he had observed:
- Every species is fertile enough that if all offspring survived to reproduce the population of species would grow exponentially.
- The populations do not grow constantly. In fact, despite periodic fluctuations, populations of species remain roughly the same size.
- What keeps population growth under control, and the population steady is the fact that resources such as food are limited, and are relatively stable over time. For these resources, there is a constant struggle between the individuals of the species.
- Members of a population vary significantly from one another, and much of this variation is inheritable.
- Those that are less suited to the environment are less likely to survive and less likely to reproduce. On the other hand, those that are more suited to the environment are more likely to survive and more likely to reproduce. Accordingly, surviving individuals pass on their inheritable traits to future generations, which produces the process of natural selection.
- Natural selection drives the changes in the species that help them adapt to their environments.
- Ultimately, the minor changes in species accumulate over time, and species evolve into new species.
Evolutionary Theory of the 21st Century
We know that evolution is a fact thanks to massive evidence from other branches of science such as paleontology, genetics, zoology, and molecular biology. Evolutionary Theory merely explains what the mechanics of this fact are, and how this fact works.
That evolution is a fact does not mean evolutionary theory will not change and get better. Facts remain the same, theories improve over time.
Evolutionary theory is, like other scientific theories, a living theory. Subsequently, as our scientific knowledge progress so will evolutionary theory.
It has been more than 150 years since Darwin discovered evolution through natural selection. In the last 150 years, many more discoveries were made in evolutionary biology that Darwin had no way of knowing at the time. As a result, contemporary evolutionary theory reflects those discoveries in evolutionary biology.
The three main differences between Darwin’s evolutionary theory through natural selection and the most current evolutionary theory are as follows:
- We now know natural selection is not the only mechanism that drives evolution For example genetic drift, could even match the importance of natural selection in the overall view of evolution.
- With the progress of genetics, the evolutionary theory now can also explain how inheritable characteristics are passed down from parents to offspring on parts of DNA called genes. The variation between individuals within a species is because of the presence of multiple alleles of a gene.
- The modern evolutionary theory asserts the gradual accumulation of small changes or mutations at the gene level. In other words, microevolution leads to macroevolution.