Darwin's Postulates

Four main factors underlying evolution


In each population, individuals vary greatly. No two are exact replicas. There are innate differences in each organism within a single species' population, and this is due to the different alleles that present sundry traits that can then be passed on to other generations. Thus, the gene pool is shuffled around.

Genetic variation is a result of genetic mutations, random mating or fertilization, and recombinations of chromatids of homologous chromosomes in meiosis, and is crucial to natural selection because the frequency of alleles increases or decreases depending on which traits prove useful for survival: the more variety, the more chances a population has at obtaining a favorable allele to keep in the upcoming generations.

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Darwin's predecessors, such as Lamark and Aristotle, argued that individuals changed their traits as responses to environmental factors, deviating from an original, universal "normal" gene. However, Darwin stipulated that traits can be passed down from one generation to the next. Although we currently take this axiom as common knowledge, at the time, this idea was quite the novelty and astounded many thinkers. Moreover, Darwin concluded that more favorable traits were passed on at a higher frequently than useless or detrimental traits.
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Selective Pressures

Selective pressures are factors that become obstacles for survival; examples include food scarcity, predation, limited space, etc. In the midst of these selective pressures, many organisms from a single population do not thrive and perish away. Because of this, in each generation, there are more offspring than those expected to survive -- species must overcompensate at first in order to prevent losing all possible life-givers.

An excellent and detailed example of a selective pressure is food: when there is only one piece of bread for 10 people, then getting the bread can be very competitive -- only those with the strength or wit get the bread, while the others are at a loss in comparison.

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Fitness and Survival of the Fittest

This is the final and token postulate: those who have favorable genes to overcome selective pressures are more likely to survive long enough to reproduce, passing on the advantageous genes to the next generation, slowly leading to the evolution of a better-adapted species.

Fitness may be contingent on physical characteristics, such as an organism's ability to camouflage with its environment to hide from predators, or another's long legs to run away more hastily; however, they may also be intellectual advantages, as we may see in humans today. Some satirists give "Darwin Awards" ironically to people who act irrationally, with no apprehensions to protect themselves from death or accidents. For instance, someone who crosses the street without looking may deserve a "Darwin Award", implying that natural selection will ensure their genes are not around long enough to be passed on to the next generation. It's a very cynical way of looking at the world, but in actuality, that is precisely what Darwin postulated. And, in the natural world, animals do not grow sheltered; rather, they grow facing the perils and obstacles and are therefore forced to compete amongst each other to survive.

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