Viagra & Evolution

Hey Peg, interesting question That still leaves plenty of males to fertilize females, so evolutionarily speaking it would not normally be a problem. Only if you combine this with a behavior pattern of mating can it result in decreased birth rates.Of course one very simple explanation is that it is a reaction to overpopulation.Enjoy.

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Thanks subbie Yes, that is what I was thinking of originally. Wonder if there was any affect on fertility as well, or would "erectile dysfunction" be a result of mental response to this same pattern in a homophobic society?Or it could just be a similar mutation to "disable" breeding when population density became high.Also it may not be genetic but developmental, due to high hormone levels at certain stages of development caused by population\breeding stress on parents\mothers. Except that the population as a whole can benefit.Consider a third "sex" such as worker bees, that allows for a large population with fewer breeders competing for mates. Which of course is no rebuttal to the concept. Consider that our social institutions have made survival of many extreme variations less problematic, so that they in effect become neutral in our ecology. Such a variation could be ages old, and a recessive gene (see Rrhain's comments)Enjoy.

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Thanks Granny Magda Rather than genetic, they could be developmental changes due to hormones and stress. People talk about stress levels in teens being high, and this is when sexuality matures.It could be something like the cues that tell non-alpha males and females in packs that they are not the breeders - look at gorillas and male dominance, if you want one close to home. Imagine this is your morning commute, every day. The last from College of Humanities and Sciences — Virginia Commonwealth University

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Anxiety Disorders are a group of serious- yet treatable- disorders that affect behavior, thoughts, feelings and physical sensations. Anxiety disorders can be caused by a combination of biological and/or environmental factors like many other disorders such as heart disease or diabetes.

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What would be interesting would be to see if there is a correlation between incidence and population density.Another interesting thing would be to compare countries to see if there is a correlation across country borders or if there is another variable involved (like the amount of chemicals in our diet compared to Europe)Enjoy.Edited by RAZD, : changed last picture

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Hey Ned,Just exploring an hypothesis here, That is one possibility. Gorillas have a dominant male pattern, so it is possible that this is a shared ancient trait.But it is also possible that it is a new trait caused by developmental cues rather than genetics - stress and hormones affecting development at critical stages, such as reaching sexual maturity.Enjoy.

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Whether the behavior of humans is natural or not, there are several aspects that are relevant:(1) this is learned behavior, and only applies to humans that have learned it or where the learning is incorporated into their society. There are places in the world where this learned behavior is not applicable - they have not learned it (incorporated it into society).(2) selection on the basis of learned behavior is still selection. This still affects the change in hereditary traits from generation to generation, it just includes more variety in the {select for reproduction (if they survive)} group and has the effect of neutralizing otherwise deleterious traits.(3) remove the learned behavior and the benefit will cease, and populations will revert to selection based on survival and reproduction without such behavior.(4) we are approaching the threshold of being able to sort through genetic material of zygotes, and remove\replace known genetic disease sections. This will result in negative selection of those traits.(5) the (over)size of the population is more critical than medical ability to allow people to survive, and as long as people starve to death, or die without medical attention, then selection is operating based on natural "fitness" for those individuals.(6) diseases still cause (natural) selection, both in developed and undeveloped portions of the world, and the spread of disease is facilitated by the global economy and overpopulation, such that a local disease can easily become a global epidemic. Bird flu as an example.Personally, I think natural selection is alive and well in the human race, in spite of our efforts to neutralize it.Enjoy.Edited by RAZD, : clarityEdited by RAZD, : dblword

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But a phenotype is not defined by one gene, no matter how much that one gene may affect the development.The question is whether the whole phenotype must be selected against, or whether there is just one gene or one gene cluster. Taking Down Syndrome as an example: Down Syndrome FAQs

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What is Down syndrome?
Down syndrome is a chromosomal disorder that includes a combination of birth defects. Affected individuals have some degree of mental retardation, characteristic facial features and, often, heart defects and other health problems. The severity of these problems varies greatly among affected individuals.

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How common is Down syndrome?
Down syndrome is one of the most common genetic birth defects, affecting about 1 in 800 babies (1). According to the National Down Syndrome Society, there are approximately 350,000 individuals with Down syndrome in the United States (2).

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What causes Down syndrome?
Down syndrome is caused by extra genetic material from chromosome 21. Chromosomes are the structures in cells that contain the genes.

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Each person normally has 23 pairs of chromosomes, or 46 in all. An individual inherits one chromosome per pair from the mother's egg and one from the father's sperm. When an egg and sperm cell join together, they normally form a fertilized egg with 46 chromosomes.

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Sometimes something goes wrong before fertilization. A developing egg or sperm cell may divide incorrectly, sometimes resulting in an egg or sperm cell with an extra chromosome number 21. When this cell joins with a normal egg or sperm cell, the resulting embryo has 47 chromosomes instead of 46.

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All one needs do is restore the normal chromosome in the offspring to allow "normal" reproduction. It should also prove instructive for our creationist friends to explain how - if all mutations are loss of information - what is lost when this chromosome is duplicatedEnjoy.

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