Clarifying Evolution

It is difficult to comprehend deep time. Our narrow 100-year glimpse of the universe makes it difficult to imagine thousands, let alone hundreds of thousands, millions, or billions of years. Our 100 years at best is a mere 0.000000025 percent of the Earth's history. Alternatively, if the Earth's history is condensed into one year, humans arrive at the New Year's Eve party with less than thirty minutes to spare. Under these constraints it is difficult to witness large-scale evolutionary changes, like those that occurred between fish and fisherman.

Evolution may have no goal, but it is not random either. Selection acts on the available traits under the current conditions, has no memory of the past, and is not propelled by an inherent need to improve a species. Chance mutation, which introduces genetic variation, may be random but selection does not act randomly. Selection favors advantageous traits, not random traits. Selection can only work with what is already there and with what is developmentally feasible. It has no foresight to plan for inevitable changes in the environment that will change what it favors in future individuals under those new conditions. Through the four forces of evolution (mutation, drift, gene flow, and selection), well-designed traits are produced through millennia of trial and error.

Populations evolve, not individuals. Although the term evolution is often poetically applied to a person's physical or intellectual development throughout life, an individual cannot evolve. A six-toed baby born to five-toed parents is not the result ofevolution unless six-toed people increase in frequency in that population over time in successive generations. Scenarios for supporting the increase of six-toeness in a population could stem from a founder effect, from a population bottleneck, or from selection preferring six toes to five.

Evolution is not the "survival of the fittest." Herbert Spencer (1820-1903) is credited for marrying this catchphrase with Darwin's theory of natural selection, but it is dreadfully misleading. As a consequence, natural selection is often misinterpreted as "only the strong survive" and, sadly, "the strong kill the weak." Fitness does not necessarily have anything to do with strength and its attainment does not necessarily require physical violence. Fitness is simply reproductive success. Individuals with favorable adaptations will survive and reproduce offspring with that favorable adaptation, thus increasing their fitness.

If there must be a catchphrase for evolution perhaps "survival of the fitter' is more appropriate. Evolutionary success is not measured in being the best. Being slightly more favored than others is enough. For example, on a continuum of short to tall people, those on the lower end of the spectrum, not necessarily the very shortest, are favored by selection if a general level of shortness is advantageous. In the next generation, the genes of the fitter ones increase in frequency compared to the less fit. The shorter individuals do not violently eliminate the tall ones from the population. The short ones simply out-survive and out-reproduce the tall ones. (This can be referred to as "out-competing," but this phrase also tends to paint an unfair kill-or-be-killed portrait of evolution.) If selection continues to act strongly on the shorter ones, eventually the tall ones will disappear or, if isolated and then favored by selection, the tall ones will continue to evolve as a separate lineage. --

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