Darwin's Postulates

The four postulates that changed how we see the world.

1. Individuals within a species are variable

2. Some of these variations are passed along to offspring

3. In every generation, more offspring are produced than can survive

4. Survival and reproduction are not random; those with favorable variations survive and go on to reproduce

Simple, yet complex.


Variation is something we experience on our day to day life. Everywhere we look, each organism has a different set of traits when compared to another organism of the same species. Let's take Ms.Rosy and Fernando Lobo as an example. They are the same specie but have different sets of traits, yes, they do have the same hair, but they have different eyes, different height, different arm length, etc. Its beautiful to think how biology allows to have astonishing variations within the same species, providing different sets of traits that may work better than others.


Here, we will be combining the second and the third principle. Around mid 1800's Darwin came to the conclusion (without having a single clue about genes and DNA) that the fathers of an organism pass some traits to the offspring. The beauty here is that genes are passed on independently, and therefore sometimes a pattern may have not be seen. These genes that are passed on, do have t come from either the mom or the dad.

As a survival instinct, more offspring are produced than those that are expected to survive. Meaning that if a pair of wolves have seven offspring, it is not because all seven will survive, but because some casualties are expected. In the wild we have predators, lack of food, weather conditions, etc, that may end up killing the great majority of these offspring. As once Ms.Leal told me ''Es mejor que sobre a que falte.''

Survival of the Fittest

Having said all this, one could ask himself; If all of these processes are in theory random, shouldn't there be the same possibility that weak traits are passed instead of strong traits? Genetically speaking, this may be true in some cases, but nevertheless, we are not considering a very important factor. THE WILD. Logically speaking, the organisms with fitter traits for their environment, will be the ones surviving while the weak ones will end up dead like a dog in the street. Hence, as every generation goes on, we are basically purifying the specie until we go on and create a more apt organism for the current environment. The weak die while the one that evolved and adapted survives, passing on these victorious genes into their offspring and improving the whole specie.


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Appenzeller, G. (2005, September 9). Hyena Serengeti [Photograph]. Tanzania.

Evansville University. (n.d.). Natural Selection. Lecture presented in Indiana, Evansville.

Honey, M. (2005). Harlequin Variation [Photograph]. London.