Evolution Through Natural Selection: Does It Apply to Humans?

This is the question I have been working on of late. We know that stick bugs, for instance, are well adapted to blending in with their surroundings. The slowly evolved this defense mechanism over millions of years until it is pretty well prefected now. As the evolutionary timeline moved forward the stick bugs that looked most like a stick survived as the bright green stick bugs were eaten by birds. (This is a hypotheitcal scenario to make a point) Over time the ones that survived produced offsring more adapted to surviving and looked even more like sticks.

My question is then how can the 'bright green' humans survive just as well as the more adapted, better suited humans? We can all see everytime we go out that don't fit the human archetype. Excessively overweight, low intelligence, lazy, etc seem to get by just as well as everyone else. How can this be possible if things evolve through natural selection? It's simple; humans are not constrained by natural selection. The reason why? Technology. We are now the top hunters on the planet even though we wouldn't be able to hunt without technology. We don't succumb to the elements and weather because of technology. We survive virus and bacteria invasions because of technology. This means that everyone can produce viable offspring with the chance to carry on unfavorable genes unlike in the 'natural' world.

Being genetically predisposed to heart disease, for instance, would noramlly get phased out over time as the organism with that predisposition would produce less offspring therefore not passing on the gene as much until it no longer exists within the breeding population.

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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 Adam Johnson on May 7, 2009 at 11:21am
To address the comment about heart disease. Heart disease is proven to have genetic origins. That aside, heart disease wasn't the focal point. It was an example to make a point. I could have made up a species and an unfavorable evolutionary adaptation, introduced technology and made the same point.

Daniel, you did a superb job with you explanation and I thank you for blessing my blog with your comment. My thesis in psychology was on myopia, cognitive myopia to be exact. You built the second floor to my arguement about humans being outside of natural selection.
Comment by Richard Haynes on May 7, 2009 at 10:15am
Carver, good point. Remind me to not post again unless I have time to develop my thoughts entirely.
Comment by Richard Haynes on May 6, 2009 at 9:06pm
Daniel, great stuff. Matthew, yeah that's what I was trying to say. ;)
Comment by Matthew F. on May 6, 2009 at 8:32pm
Natural selection can't apply to modern humans. We are diverting evolution with our brain power (or lack of it in some cases).
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.
Comment by Mikey Granule on May 6, 2009 at 2:44pm
Who said you had a problem with vegetarians? I didn't.

Survival of the fittest can be made to fit any theory about human characteristics past or present, as I think you are neatly demonstrating.

Thanks for the debate by the way, sorry you're not interested in it.
Comment by Richard Haynes on May 6, 2009 at 2:13pm
Okay, you are missing the point entirely. Let me again say, I don't have a problem with vegetarians. My daughter is one. They are "we" as in "our" ancestors. "We" have benefited from what "they" did.

I'm really not interested in debating you. Just trying to give my comments on Adam's question. Do you have anything to add?
Comment by Mikey Granule on May 6, 2009 at 2:01pm
We? These meat-eaters are not part of my we. They are not even your we. They are their they. We have nothing to do with them.

Keep thinking!
Comment by zeeman barzell on May 6, 2009 at 1:54pm
Movie of the week: Idiocracy
watch it.


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