The Four Darwin Postulates

By: Emilio Marino

Postulate #1

The Potential For A Species To Increase In Number

This postulate is very important for evolution to occur within a species because as a species increases its number, more variations within the genes occur. This postulate has a very simple definition but is vital for evolution and is seen in any species around the world. For example, what was once a vulnerable species, humans had the potential to increase the overall population. As diseases like the black plague fell over the race, thanks to the large number humans, the species was able to survive the epidemic. Overall, allowing species to reproduce and grow makes the species more resistant to diseases and threats because as the population increases many different variations within the genes are produced that helps the species adapt and survive in the long run.

Postulate #2

The Heritable Genetic Variation of Individuals In A Species Due To Mutation and Sexual Reproduction

This postulate is very important because it shows that genetic variation is heritable. Heritable genetic variation can be seen in the increase of dominant traits through generations and generations. For example, in the game I played in Biology I was able to see how through generations, the dominant trait even though if it was set as a mutation, was passed on to the next generations. So, bunnies living in the arctic and we placed brown bunnies as dominant and white bunnies as recessive, the white trait was passed on through generations. The simulation game I played backs up Darwin's postulate that heritable genetic variation in a species is passed on to the next generation.

Postulate #3

Competition for limited resources

In the world there are only certain amount of resources that we have. Due to this, in each species a generation produces more offsprings that can possibly survive. This is when the idea of competition comes in. Only the strongest, fastest or smartest will consume the necessary resources to survive leaving the weakest to die. This can clearly be seen when a dog gives births to its puppies. Regularly, there are too many puppies and only a certain amount of milk the mother can give to her offsprings. Because of this usually one or two puppies are pushed aside by its brothers and cannot survive because of the lack of nutrition. When offsprings need to compete for vital resources the fittest are the ones that obtain them and ensure their survival, the others are left behind. Competition for food and water helps regulate the population of a species and ensure that the "best" offspring is the one that reproduces to improve the species as a whole in the long run.

Postulate #4

The proliferation of those organisms that are better able to survive and reproduce in the environment.

This final postulate basically sums up the three postulates before. It basically states that organisms with the fittest gene for the environment will pass on their gene onwards to the next generation. For example, the Ichthyostega was an aquatic animal in the Devonian period that had small limbs that allowed the animal to walk on land. Eventually, this gene started to pass to its ancestors and eventually created the Tetrapods. The Ichthyostega's that did not have those small limbs did not pass on their genes, which clearly demonstrates the fourth and final postulate of Darwin. Thanks to this postulate the more fit descendants are represented in the next generations and so on and so on.


Freeman, S., Allison, L., Black, M., Podgorski, G., Quillin, K., Monroe, J., & Taylor, E. (n.d.). Biological Science (5th ed.). Pearson.

Garner, P. (2003, August 1). Fossil Record of Tetrapods: Evidence of a Evolutionary Transition. Retrieved February 28, 2016, from

Johnsen, Z. (2016). Fading Puppy Syndrome. Retrieved April 05, 2016, from

U. (n.d.). Introduction to Ecological Genetics. Retrieved April 05, 2016, from