Ecology and Evolution

What is fitness in relation to natural selection?
Answered by Science Channel
  • Science Channel

    Science Channel

  1. If you've ever heard the saying, "look out for number one" this theory will be easy to understand. "The Selfish Gene" reframed evolutionary thought in the 1970s. Richard Dawkins stressed that natural selection favors the passing of genes and not the organism itself. In other words, natural selection only truly promotes successful and prolific reproduction, not the individual success of an organism.

    Certain questionable traits continue to exist, ones that may harm the organism but benefit the genes. An example is found in many spider species where the female devours the male after mating. The argument could be made that being a good meal is a bred trait for male spiders, ensuring continuation of their bloodline; or perhaps female spiders could just be opportunistic feeders that prey upon smaller males [source: DailyScience]. Either way, if the male wants to pass his genes on to the next generation, he must take his chances with the female.

    Fitness, or biological fitness, is the key to natural selection. It is the ability of an organism to successfully survive long enough to reproduce. It is also the ability of an organism to reproduce well. For example, a tree's biological fitness depends not only on its ability to grow and thrive, but, more importantly, on its ability to produce many seeds that take root and eventually produce seeds of their own.

    Many biologists agree that Dawkins' ideas add to the explanation of natural selection. However the idea that people and animals are shaped only by millennia of opportunistic gene-passing has brought up the question of altruism: In humans, is altruism just a manifestation of our genetic need to elevate ourselves within our social groups, thus putting ourselves in a position where our genes can continue into the future? And if so, is there really anything that can be defined as a selfless act? Or are we just following ingrained patterns when we think we're doing good? It's a philosophical question that mathematician George Price grappled with. In true mathematical form, he first proved that selflessness was tied to genetic selfishness. Then, disheartened by the findings, he attempted to prove that altruism could exist [source: RadioLab].

    The answer to the question of altruism and the selfish gene in humans is murky and undefined, but Dawkins suggests that the human brain -- which was shaped by Darwinian natural selection -- eventually developed to a point beyond the rules of evolutionary theories. For instance, our ancestors didn't die off during the Ice Age, nor did they start growing fur; their intellect developed warmer protection (clothing). And humans have developed medicine to defend against sickness rather than letting every epidemic run its course through the population. A so altruism and morality may be products of humans' new way of the dealing with the world around them -- and perhaps the selfish gene is not so selfish after all.

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