The murky future of the human gene pool

A conversation I had with a friend made me realize something interesting. Modern medical technology is responsible for the constant degradation of the human gene pool. How? Simple, we allow bad genes to propagate.

Take me for example. I have glasses. Quite a small diopter, but glasses nonetheless. In ancient times, my eyesight genes would have had a negative "evolutionary" pressure from the environment. I would have had for example a somewhat degraded chance to successfully hunt my food, lower probability of noticing a stalking tiger, and hence a higher chance of dying before getting to reproduce. Namely, my bad eyesight gene would have had a somewhat smaller probability of successfully propagating itself, and hence would tend to disappear relative to the better eyesight genes.

Today, this is not the case of course, given that I can readily obtain glasses, my bad eyesight gene has just as much a chance in propagating itself as the better eyesight gene. Since the bad gene stands an equal chance in reproducing itself, it wont die away. Of course, there are many other examples like that. The most extreme would be of course a hypothetical gene which causes infertility that can be circumvented by other means (e.g., with IVF - In Vitro Fertilization). Such a gene would have died off after a single generation, but can now easily propagate until the end of eternity.

This implies that bad genes can now accumulate without necessarily dying off. Of course, if they don't have any evolutionary preference, i.e., they are "neutral" (e.g., if it just as easy for glass wearing geeks to get married), it would take a long time for such a gene to become important (if it doesn't accidentally die off otherwise), since it would require a random walk in the gene pool for it to become dominant.

Is this bad for humanity? Clearly, if a gene can now propagate itself by an artificial mean, it would be able to do so in the future, it only implies though that we will have to rely on more and more means. That is, it would be progressively more expensive, and complicated to keep the human race "reproducing".

Of course, I am not the first to think about this point. Many years ago, I read a book by Arthur C. Clarke called Imperial Earth. The background story is about a guy who lives on Titan (a moon of Saturn, which happens to be the only planetary moon in the solar system to posses an atmosphere, but that's just an anecdote I couldn't help myself from mentioning), and takes a trip to Earth to clone himself. Why? Because he is totally sterile, and so was his father and grandfather...

Makes you wonder what humanity will look like in say 500 years. Doesn't it?


Comments (11)

  • anon


    Your comment is interesting, but maybe it's not so simple. The "bad eyesight" example doesn't quite work. Humans (homo sapiens, not counting our ancestors) had gone through a few 100,000 years of evolution by the 17th century, when glasses were invented, yet bad eyesight was still common among humans. If it was such a bad gene, it would have disappeared a long time ago.

    But nevertheless, the question of how our "modern" lifestyle will affect the evolution of our species is fascinating. We should just be careful not to jump to easy conclusions!

    Take another example: humans are smart, no question about it. But not THAT smart! Yet we value intelligence a lot, and one might wonder why we have not evolved to be even SMARTER! Even a 10% higher average IQ could make a huge difference. But on the other hand, we evolved as hunter gatherers, and even though our intelligence apparently gave us a huge advantage, the physical constraints to be even smarter (larger, heavier brain?) must have outweighed the advantage of being smarter. Our intelligence was "just right" for the lifestyle we have had for tens of thousands of years. But is it still the case, especially since we changed our way of life about 10,000 years ago with agriculture, followed by the industrial revolution? Intelligence is more and more important in today's world. Are we growing smarter? If you think climate proxies are a difficult subjet, imagine how difficult it is to figure out the average IQ of humans 20,000 years ago!

    Jul 16, 2006
  • anon

    Good point Francois
    Higher IQs are found to be related to a thicker prefrontal cortex (if I'm not mistaken). And either way, a larger, heavier brain would require more energy to grow. (As can be seen in studies done regarding placental and milk-drinking mammals.) This would mean that "the physical constraints to be even smarter (larger, heavier brain?) must have outweighed the advantage of being smarter," even today... Gestation periods would have to increase and 9 months is long as it is!

    Nov 20, 2010
  • anon

    This is an interesting topic which I have found difficult to research. Assuming that 50% or so of humans today need eyesight correction, was this the average 500-1000+ years ago. We need to consider the aging population, such that 1000 years ago the average lifespan was about 30 years, and you were a wise elder if you lived to be 50+.
    Early astronomers and scientists must have been the few persons with near perfect eyesight. I don't have the worst eyes, but I sure as heck can't see stars at night. Were half the people who assembled Stonehenge wondering what the heck they were doing, since they had no clue about movement of the heavens? I require about -2.75 diopter correction and wouldn't be able to tell friend from foe from 50 feet. Does that mean I would be considered a blind person 1000+ years ago? Would they have allowed me to go on a hunting party?
    Getting back to your question about evolution, I think your point is valid. Sickly and defective people are allowed to propagate. Will future generations require more and more medications, vaccinations, antibiotics etc.. I would think so.


    Dec 12, 2006
  • anon
    Johnboy (not verified)

    Good genes, bad genes. Don't you think we're in danger of going too far in trying to blame and control everything through genetics? It's certainly no brave new world ahead of us in the next half millenia.


    Apr 14, 2008
  • anon

    I have thought about this before. I believe that the technology that we use to prolong the lives of people that would naturally have died off, is the reason for many of the problems we are seeing now. I also believe that this may be the downfall of the human race. Cancer rates are much greater in people now and for no discernible reason. I for one would have died as an infant if not for modern medicine. I think that this maybe a slippery slope, which could eventually become irreversible. This maybe the devolution of the human race.

    Jan 27, 2009
  • anon

    I should say that new technology will completely replace natural evolution. Genes will be able to be manipulated for the better, cybernetics will be a huge part of our future and "singularity" is probable in the not too distant future. 500 years from now? We will have transcended natural evolution.

    Mar 01, 2009
  • anon
    Bob (for better... (not verified)

    When modern education was first introduced into Alaska, studies were made of the eyesight of students and parents. While parents and grandparents had almost no eyesight problems, about 60% of students suffered vision defects.

    This is almost a death blow to the idea of inheritance.

    Most people today do not consider vision problems to be inherited. While genetic defects in the eye do occur, WebMD indicates: "Many people have believed for a long time that too much close work, such as reading or sitting too close to the television, causes nearsightedness. One study suggested that people who have jobs that involve large amounts of reading do indeed have higher degrees of nearsightedness."

    I believe that general tension and environmental factors can cause eye problems. And, so, proactive steps can be taken to improve eyesight. I have recovered over 20 years of deteriorating eyesight and am still improving.

    May 15, 2009
  • anon
    neil cashman (not verified)

    This is something I think about all the time. How we have messed with natural selection. And, the interesting thing is, how controversial this idea is.

    Imagine if we did use the idea that the strongest will survive...Can you think of all the contorversies? Forget about glasses, what about major birth defects like paralysis, deformity, mental retardation.

    Who and how would someone decide the selection...

    And forget about the abortion topic!


    Sep 26, 2009
  • anon

    One day we may have genetic manipulation so that the current proliferation of 'bad genes' might really be of no negative consequence. In fact, the sheer variety of humans that exist as an effect of modern medicine probably increases the chances that a genius might appear who would lead us to the means of such manipulation.

    Sep 27, 2009
  • anon

    I have a question for all of you. Actually a couple questions, with information.

    1.) The term "Survival of the Fittest" may be an obsolete term; but, for how long? You must take in account that something may disrupt society in some way; such as Katrina, it became survival at that point, just with a different outlook and definition. It was either go out there and get back on your feet, or sit there and die.

    2.) As for the bad gene discussed about. We do have bad genes today, some created because of medical science. There have been reports that the "Swine Flue" vaccine causes Alzheimer; not only that, recently released by these medical scientists that created the vaccine released it as a possible "reaction" caused by the vaccine.

    Not trying to discredit everyone, just sharing some information. Like most people I do believe a right to your own opinions and theories. You may believe or disbelieve the information presented; but do not just pass it off without at least giving it some though.

    Oct 18, 2009
  • anon

    I'm not sure preventing people with small defects to get married is a good idea.
    it would be better if one could alter one's DNA before propagation or use an altered form of their DNA to propagate.

    Oct 05, 2011