Viagra & Evolution

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Of course one very simple explanation is that it is a reaction to overpopulation.

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Interesting suggestion. I have a couple of observations, though.I'm reminded of something I heard, quite some time ago, about an experiment were researchers kept mice in extremely over crowded conditions and discovered that some of the mice became sexually attracted to members of the same sex.Wouldn't your suggestion and the experiment that I recall (if I'm recalling accurately) mean that, in effect, evolution is operating to the detriment of some individuals in favor of the rest of the population? If so, I must admit that I'm hard-pressed to conceive of an evolutionary explanation for such a phenomenon. It seems counter intuitive.

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Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin FranklinWe see monsters where science shows us windmills. -- Phat

Hi, Peg. No. Percy and Huntard have already addressed this, but I always like to add my own little bit, too.The result of natural selection is generally that something "less fit" dies or fails to reproduce. But, since we can make people that are "less fit" survive and reproduce, we are not allowing natural selection to remove unfitness from our populations. We're actually facilitating the propagation of unfitness, which is antithesis to evolution by natural selection.Percy has commented that humans are apparently evolving faster now than we were anciently. I'm not sure if I fully accept that, but I haven't thought it through carefully enough to comment. But, consider this: if we are allowing everybody the opportunity to reproduce, we are preventing natural selection from driving many "unfit" traits to extinction, which ultimately will result in more persisting diversity in our populations. So, maybe that's what Percy's source was saying.

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-BluejayDarwin loves you.

In essense, we as the human species are commencing artificial selection on ourselves, much like we do when we selectively breed domesticated animals and plants to produce food and other resources that we need. Thus these artificially selected factors we place on ourselves overide the naturally selective processes which would naturally shape the genome of the human race.

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For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring.
Dr. Carl Sagan

What are you talking about? People die premature deaths all the time for many different reasons, and the ones that survive to reproductive age do not all reproduce at the same rate, if at all. Evolution is alive and well, thank you.

We've been doing that for a long time. Sexual selection is one instance.

Peg writes:

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there are many couples who need ivf treatment to conceive these days, men are becoming impotent, sterility issues... how does evolutionary science explain this phenomenon???

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Where in "evolutionary science" does it say that all members of a species are supposed to reproduce? You are making an assumption that is not justified. Evolution doesn't care if everybody reproduces. Only if enough do.Considering that the human population has literally exploded: It does not appear that the occasional infertile individual is a problem. We are in no danger of extinction due to sterility.

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Rrhain

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Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

fallacycop responds to Bluejay:

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But, since we can make people that are "less fit" survive and reproduce, we are not allowing natural selection to remove unfitness from our populations.

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What are you talking about? People die premature deaths all the time for many different reasons, and the ones that survive to reproductive age do not all reproduce at the same rate, if at all.

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Indeed. The fact that there are some fairly direct ways of killing a person off before puberty, however, doesn't change the fact that our modern technologies of sanitation and medicine have made it possible for people who would have died before puberty to survive and thus have the opportunity to reproduce.Smallpox literally does not exist anymore. It used to be the leading cause of death. We've eradicated polio for all intents and purposes in most of the world. There's a reason they're called "childhood diseases" and they used to be quite fatal. If you made it to your first year, you were quite lucky.But we've figured out how to vaccinate and thus prevent people from catching the diseases that would have killed them off. We no longer have that environmental factor affecting our evolution. The reason sickle-cell trait exists at all is because of malaria. Being heterozygous for sickle-cell provides a fair amount of protection against malaria. Since we no longer have many diseases affecting us, where is the selective pressure to develop traits that fight the disease?We are seeing such a thing with HIV: There are some people who carry a gene such that their white blood cells do not have a protein that HIV requires in order to infect it. Thus, they seem to be immune to it (or, at least, certain strains). In a population that has HIV as a selective pressure, this trait would start to become more prevalent.But suppose HIV didn't exist: What would be the selective pressure to make this trait common?The fifth leading cause of death for all people is accident and for young people, it is the leading cause of death. Our ability to keep these people alive and thus survive to reproduce means the selective pressures that would affect behaviour and body morphology with regard to survival are not nearly as strong as they once were.It isn't that there are no environmental pressures on us, but we have severely limited the effects of many. Do you really think that a population that developed sunscreen and used it religiously would have the same diversification of skin tone that a population that didn't have such protection would?

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Rrhain

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Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

I stand by what I said. Evolution is alive and well, thank you. The fact that we have changed the enviroment to such an extent that old evolutionary pressures do not have the same impact that they used to have does not mean that evolution stops. New evolutionary trands will replace the old ones.

I agree with you. A change in our genome is a change in our genome whether it is artificially induced by an outside intelligence i.e. artificial selection by humans or by naturally generated mutations guided by natural selective pressures i.e. sexual selection, dying off of weaker organisms, genetic drift, etc. Either way they are both part of the evolution of our species.

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For me, it is far better to grasp the Universe as it really is than to persist in delusion, however satisfying and reassuring.
Dr. Carl Sagan

Hi rueh,Sorry for the delay in reply, I've had a busy couple of days. I completely agree. The distinction I was trying to make was more that the increase in male fertility/sexual problems is usually directly attributed to environmental factors (pollution) rather than genetic. Makes sense to me, but only if there is a genetic basis for resistance to the appropriate pollutants. If alleles exist that can protect against environmental damage during development, I suppose we would expect to see the trend you describe. I would say though that medical know-how can fix some of these problems, allowing couples with infertility problems to have children nonetheless. That would presumably dilute the effect.Unfortunately, I think the trend is currently still toward an increase in male infertility etc., so I can't imagine that genetics is a significant factor as yet.Mutate and Survive

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"The Bible is like a person, and if you torture it long enough, you can get it to say almost anything you'd like it to say." -- Rev. Dr. Francis H. Wade

Peg, Yes. Another way of saying that is that less than 10% of sufferers are under 30. Note that I said "It tends to happen to older men. My earlier points still stand.Evolution will always act to reduce the frequency of harmful traits in a population, but there is no reason why it would necessarily wipe them out entirely. So long as the population as a whole can survive the negative impact of a trait, it may persist, especially if the trait is not expressed in everyone who carries it (such as in the case of a trait controlled by a recessive gene).Remember, all this is only really relevant where there is a genetic basis for the dysfunction. As has been noted above, there are a number of other causes for erectile dysfunction, infertility, etc. and telling cause from effect in so complicated a phenomenon is way beyond my meagre talents. Mutate and Survive

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"The Bible is like a person, and if you torture it long enough, you can get it to say almost anything you'd like it to say." -- Rev. Dr. Francis H. Wade

Hmmm... Is that a simple explanation? I'm not so sure it is. What would the mechanism be? What cues would "tell" the body that it is living in an overpopulated environment?The world may be more overpopulated than ever, but it is hard to see how individuals living in cities are any more crowded than those who have lived in urban environments for centuries.I'm not saying that your explanation is wrong; I've heard it many times before and it is a tempting conclusion. I just find it hard to picture how it would actually work on the ground.Mutate and Survive

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"The Bible is like a person, and if you torture it long enough, you can get it to say almost anything you'd like it to say." -- Rev. Dr. Francis H. Wade

fallacycop responds to me:

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stand by what I said. Evolution is alive and well, thank you. The fact that we have changed the enviroment to such an extent that old evolutionary pressures do not have the same impact that they used to have does not mean that evolution stops. New evolutionary trands will replace the old ones. I stand by what I said. Evolution is alive and well, thank you. The fact that we have changed the enviroment to such an extent that old evolutionary pressures do not have the same impact that they used to have does not mean that evolution stops. New evolutionary trands will replace the old ones.

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Evolution is not merely mutation. This is something we keep bashing our heads against the wall in trying to get creationists to remember. It is not helpful when we forget it ourselves.Evolution requires a selection differential. Selection is the driver of evolution, not mutation. If our technology allows us to make it so that those selection differentials vanish, how is there evolution?Now, I personally don't believe that we have managed to do this for all selective pressures. But we have managed to do this for a huge number of them. The reason why the average lifespan of centuries past was so low was because chances were very good that you were going to die before you made it to 5.Average lifespan in developed countries is now pushing 80 years. That means the overwhelming majority of people are going to make it to reproductive maturity and given the explosion of our population, a huge number of those individuals are actually going to reproduce.Where is the selective differential if everybody makes it to maturity and reproduces? Evolution depends upon the fact that some morphologies don't reproduce. If everybody does, then the driver of evolution vanishes and we are left with mutation.

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Rrhain

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Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.

and if most humans reproduce then the larger population with have very great genetic diversity. A change in gene frequencies of populations over time is what evolution is.It will continue even if we do reduce selective pressures. By the way, I am in agreement with you that we have not reduced all pressures and I think we have increased some. For one, our denser populations are probably putting pressure on to help select "tamer" humans.

Peg writes:

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except that its seen in men as young as their early 20's
1 australian site says that almost 10% of sufferers are in their 20's

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Others have responded to this, but the answers are in the abstract. I want to give you something more hands-on and direct.This was a homework question from my intro-bio class in college:Suppose we have a single-gene recessive trait that has an expression of 1 in 1,000 in the current population. That is, the trait is controlled by a single gene of which there are two variants, p and q. One allele, p, is dominant while the other, q, is recessive and the only way to express the recessive trait is to be homozygous recessive: qq. Anybody who is pp will not show the trait nor will anybody who is pq since the p allele dominates.Assuming we could control reproduction such that nobody who expresses the recessive trait reproduces (that is, all qq individuals do not reproduce with anybody), how many generations would it take for the frequency to go from the current level of 1 in 1,000 to 1 in 1,000,000?The point is that even when we are actively trying to reduce a trait's appearance in a gene pool, it is extremely difficult to make it go away. And since we do not have the perfect reproductive control that the question above demands, it is clear that real-word scenarios will be even more difficult.The trait persists because it isn't a barrier to continuation of the species and having it go completely away is hard.

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Rrhain

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Thank you for your submission to Science. Your paper was reviewed by a jury of seventh graders so that they could look for balance and to allow them to make up their own minds. We are sorry to say that they found your paper "bogus," specifically describing the section on the laboratory work "boring." We regret that we will be unable to publish your work at this time.