Life on Earth
by Tom Edathikunnel
Part II: Survival of the Fittest
The term survival of the fittest is used by both evolutionist and skeptics, often without a complete scope of its context and application. The term is not a measure of traditional physical fitness or even a measure progress; in fact the idea of linear path in evolution goes against the very nature of the theory. Fitness in the evolutionary frame can be deconstructed to a simple principle: Those who reproduce are those who survive.
Now this principle may seem obvious but it ties back to the core component of evolution, which is that those who are the most adept at reproducing in an environment, better known as the “fittest”, are those who leave more descendants.
Fitness is not measured by strength, intelligence, or speed, and while these are contributing factors, they are merely a result of the process. Survival is dependent on the adaptability to ones environment and the ability to reproduce within it; hence, the natural selection of a species’ lineage.
An organism capable of reproducing is the species that is evolutionarily going to excel and perpetuate. Speed for catching prey can be an advantageous trait that aids in the reproduction of one’s genetic material, (by catching more food more of that predator can survive, grow, and reproduce), however when that trait no longer yields a reproductive benefit, it ceases to be “fit”.
Examine this conception of fitness in the broadest sense possible. All animals on earth utilize oxygen and the main biological component for respiration. But the Earth’s atmosphere at one point contained mostly carbon dioxide, meaning that organisms that used oxygen for metabolic function would cease to be “fit”.
The great Oxygenation Event, is a time in Earths geological past that makes the sudden introduction and retention of oxygen in earth’s atmosphere. Taking place approximately 2.4 billion years ago, organisms that relied on higher levels of carbon dioxide to survive began to go extinct, unable to reproduce to the changing atmosphere.
Organisms that thrived in an atmosphere of greater oxygen content began to leave more decedents, and ultimately perpetuated the diversity of animal life we see today.
More specific influences can be seen in modern evolutionary trends and breeding techniques. As previously mentioned, fitness is the success of reproduction, and with complex creatures, mating and sexual expression play a larger role. Species with sexual reproduction have the largest diversity in form, which can be contributed to sexual selection.
For example, males in large mammals and birds often have ostentatious traits, whether that is colorful feathers, full manes, large antlers, long necks, horns, etc. These may not be functionally efficient- colorful plumage is taxing process to maintain and can make birds more obvious to predators – but it is advantageous or “fit” for sexual reproduction. Meaning that while large antlers can be physically cumbersome they are effective for thwarting other males and is a necessity to reproduce.
Thus, survival of the fittest is a dynamic idea, not limited to a particular attribute or skill. Through environmental challenges and reproductive success, the animals and plants around us continue to change and evolve. As conditions change, so too do the traits that make us “fit”.