Evolution Through Natural Selection: Does It Apply to Humans?




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Comment by Daniel W on May 9, 2009 at 9:38am
Adam, thanks.
I think I'm too wordy and am trying to control myself! There aren't other places where people can discuss the topics that we discuss here on A|N.

I agree with the heart disease issue, except that it's rare for people to die from heart disease while still in the usual reproductive years. Most people in ancient times died young - 20s, 30s, 40s. Cause was violence, poor sanitation, disease. But I get your point.

It would be interesting to see a synopsis of cultural myopia. Probably off topic for this post, however.

Comment by Daniel W on May 6, 2009 at 3:40pm
I would like to contribute 2 cents to this discussion.

Adam's point about the consequences of technology on natural selection is valid. Adam, the example could use some work, however. Let's change the example to myopia and roll it into Richard's argument about omnivory.

Before starting, on that topic, the vegetarian aside should be handled separately. As for past evolution, human teeth have specialization suitable for both animal and plant diet, indicating that we are evolved via both. Note that I don't state evolved FOR both, which is a subtle differnence. Our metabolism also absolutely requires vitamin B12, which does not come from plant sources, and a complex mix of amino acids that can be achieved either by animal sources or mixed plant protein. I am vegetarian for my own reasons, and understand that in today's world meat is not only, not required, but actually harmful in many ways.is not the nissue for past past evolution. This has a place in our own, planned survival as a species, being future planned selection, which is not the same as natural selection.

Back to myopia, if we were all out in the savanna chasing wildebeasts and running away from lions, it makes sense that we need to see them clearly. Especially those sneaky lions. Given that life expectancy was much shorter, someone who was eaten by lions was probably of reproductive age, so a nearsighted person's genes would be lost to the gene pool. Even more to the point, once we developed spears and arrows, we need to be able to aim them. Those with poor vision would not have survived. Once agrarian society developed, good vision was no longer such a necessity, because you really don't have to see well to plant crops. And now, with technological vision correction of many sorts, poor vision has no negative consequences for reproductive fitness. So with genetic drift, it can be expected that vision in the human species would continue to deteriorate. because there is no longer selective prossure FOR good vision.

More extreme examples can be found with decreased immunity (one of Adam's points). Humans don't really need the immune function that they once had. Probably all of us would be dead if not for some timely antibiotics at some point of our lives. If not that, then the vaccines that we have received. However, we DO have the antibiotics, and we use them, so a decreased immune function does not decrease our ability to reproduce.

Adam, if that's not your point, please forgive me for chiming in.

As for the future direction, since the world is no longer 'natural' but a produce of our own making, some genes that were once required are not any more. Such as good vision, mentioned above. I think that our future survival depends less on our genes than on our memes. If all that we do is reproduce to the point of oblivion, use resources until they are gone, pollute to the point where the planet is not habitable, then our species will die out more quickly than we had hoped. If we develop the cultural strategies and memes to create planned roles in the earth's ecosystem, reduce pollution, reduce population pressures, then our species should survive longer and continue to evolve longer. We need to eliminate or contain the religious memes that make it OK and even desirable to reproduce like bunnies (Catholics, Mormons, Islam), or make it OK to use up all resources because 'the end is near anyway' - evangelical christians, Islam. A nuclear winter may be less likely now than 20 years ago, but let the Taliban take over Pakistan and see the West start to shiver.
Who said you had a problem with vegetarians? I didn't.




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