Since life first evolved on Earth, a huge number of species have developed only to subsequently become extinct, a key feature of Darwin's 'survival of the fittest' model of evolution. A number of species face extinction today - is it right for mankind to intervene to try and stop this process?

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Saying that natural selection favors the "fittest" creatures makes it sound like interfering would obviously be bad because it would risk diminishing a good thing, namely fitness.

But first of all, there is nothing in Darwin's explanation of natural selection that assigns any value, positive or negative, to reproductive fitness. The central idea, of course, is that when genetically passed-on traits cause members of a species to have more descendents than others, the traits become more common. That has nothing at all to do with whether the outcome is "for the best" in any sense. It's just what will in fact happen.

And secondly, the role of humans in a way changes nothing: we are part of the enviroment, and our behavior affects the natural selection of other species fundamentally no differently from any other environmental factor. Our fondness for juicy oranges or annoyance with intrusive coyotes can explain why certain organisms have more or fewer offspring than others in the same way that facts about climate and competing species can. Similarly for our preference, say, for biodiversity, or for slowing the rate of extinctions caused by others of our behaviors. "Fitness" can just as easily be the capacity to thrive in a nature preserve as the capacity to survive in a sewage-thick bay. So our "interference" can be seen, not as counteracting selection of the fittest, but as influencing which organisms, with which traits, will in fact exhibit fitness.

Still, to point out that the basic theory of natural selection has no consequences about what it would be right or wrong for us to do in influencing its course leaves completely open what considerations really do bear on the moral issue. Surely there are practical concerns---we might one day have use for many of the species that are dying out (and who knows which ones?); the effects of extinctions on ecosystems may be of serious practical concern for humans. Are there, in addition, more purely moral reasons to favor a conservative approach to our custodianship of the planet's biodiversity? Do we have duties to species or to ecosystems, or responsibilities to future generations to leave things not so impoverished from how we found them? Someone should ask a philosopher.

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