How do scientific advancements in medicine and other fields that are intended to help the weak, ill, disabled, those with unfavorable traits, etc… effect natural selection? If natural selection allows for favorable heritable traits become more common in successive generations, but scientific advancements allow the weak with unfavorable traits to live longer and pass on their genes, how do the two effect each other?
Interesting question. Natural selection is really about the ability to adapt to whatever the world throws at you.
If a technology allows people to live longer, that won’t do anything to the gene pool since it affects people past their reproductive years.
A technology that prolongs the life of those affected with diseases associated with childhood deaths could increase that allele in the gene pool - assuming the patients reproduce and the allele is passed along.
You might get some people arguing with your use of “unfavorable traits” but I won’t get into that.
A larger factor affecting our gene pool might just be beer. If you haven’t seen the movie, “Idiocracy,” I highly (pun) recommend it!
The other thing to remeber is “weak, disabled, etc” only have meaning in the context of the selective environment the animal is currently in. Myopia might or might not have been a meaningful disadvantage from an evolutionary point of view in the environment of hunter-gatherers w/ limited technology, but it is clearly irrelevant to survival and reproduction now. Ameliorating it with technology only “helps the weak” if it is expected someday we will have to go back to such an environment. If the duration of our species’ survival is in a technological mileu, such things should have no selective meaning. If we nuke or otherwise blow ourselves back to the stone age, then such traits might again be a liability and be selected against. But we have to be careful of this notion of “weakness” that eugenicists in past generations promoted, since it’s evolutionarily meaningless unless the specific selective environment is specified.
FWIW, I’m one who thinks we largely create our own selective environment now, with the exception of infectious organisms which we still battle directly, not just through the mediation of technology. This doesn’t mean we aren’t evolving still, but the pressures that created what we are now are hundreds of years in the past, and technological change is so rapid that I’m not sure we can even guess at what might be happening to us genetically since the time scales of genetic and cultural/technological change are so different. We are certainly becoming even less genetically diverse, as people move and mate more freely than ever, which might create some hybrid vigor but might also be reducing the genetic diversity available to respond to a sudden, new selective force, such as an emerging disease.
Interesting stuff, but all rank speculation given how hard it is to see things from an evolutionary timescale.
As long as there are selective pressures on a species natural selection continues. The human race is still subject to natural selection, the selective pressure have just changed. Exactly how is debatable. I’ve often thought that lower intelligence( or at least lower education) is being selected for since those with the least education have the most kids in our society and visa versa, but that assumes that educational level is linked to some genetic trait that can be passed on.
You could certainly argue that any anything that causes deaths ( or decreased fertility/ lower fecundity) in people of reproductive years could be a selective pressure if it is linked to a genetic trait. Homicide, HIV and Motor vehicle accidents are some of the most frequent causes of death in men under 25. If you can identify a gene that makes someone more likely to be violent, drive aggressively, or engage in IV drug abuse or risky sexual behavior, that gene will probably be selected against over the course of time assuming those selective pressures don’t change. You have to keep in mind that evolutionary changes take thousands of years though and selective pressures may change before any evolution has a chance to occur (We may run out of gas long before nature has a chance to select out the gene that causes aggressive driving).
The bottom line is natural selection never stops. The selctivepressures just change
mckenzievmd - 17 May 2008 03:22 PM
We are certainly becoming even less genetically diverse, as people move and mate more freely than ever, which might create some hybrid vigor but might also be reducing the genetic diversity available to respond to a sudden, new selective force, such as an emerging disease.
Interesting stuff, but all rank speculation given how hard it is to see things from an evolutionary timescale.
While we usually agree on most things I don’t believe this is completely accurate. Natural selection may cause a greater diversity of species, but it actually results in less genetic diversity within a species. By killing off those individuals who are “less fit” the gene pool actually has less variety.
I’m not sure I see a disagreement here. I wasn’t implying that a selective force, like a disease, would increase genetic diversity. I don’t think it would, unless the population was diveided into separate gene pools subjected to different selection pressures, founder effects and so on. This, then might lead to greater diversity within a species, or eventually a speciation event. All I meant was that the increased mobility and interbreeding of previously isolated human populations was reducing the diversity of the species. This has potential implications since species which pass through a bottleneck and have low diversity may not be able to cope as well with intense new selection pressures, such as a disease, because the low diversity reduces the chances of a subset of the population that might be more resistant to it than the population as a whole.
Sorry, I misunderstood what you were trying to say, but even with increased mobility the genetic diversity would still be there just not in the same way. Instead of distinct genes being clustered in Asian, African, American groups, those genes would now be dispersed throughout the globe. While we might all start to look more alike because of interbreeding, the gene pool might actually not change much at all, unless world wide selective pressures became more similar everywhere than they were in the past.
Hmmm. I guess we need an evolutionary geneticist to help us here. As I understand it, if you mix a small, previously isolated group with unique combinations of genes with a larger, more homogenous population, several things happen. Obviously, the frequency of specific genes decreases since the pool is automatically larger. But more importantly, with successive generations, gene combinations which were at high frequency in the small population but now low frequency in the mixed group begin to get dispersed, so those unique combinations are less likely to be available. Whether or not specific alleles persist or disappear depends on the factors that influence the reproductive success of individuals with those alleles. The alleles from the small population may persist at a low frequency or even gradually increase in frequency in the larger, mixed population depending on their fitness. Still, I think as a small group gets absorbed into a much larger one, the number of unique gene combinations or sets decreases. The number of different gene combinations could be one measure of genetic diversity.
In any case, humans have, as I understand it, pretty low diversity compared to many mammalian species anyway. A popular theory suggests our migration out of African constituted a “bottlneck” event, and in fact there is far more diversity among African populations than the entire rest of the species. And there seems to be some controversy, which I’m not qualified to have an opinion on, about whether human genetic diversity can be meaningfully described as discontinuous among isolated groups, consistent with cultural, linguistic, or traditional racial markers of distinct populations, or evenly distributed geographically as clades. An interesting topic, for sure. I know that amog dogs, which are highly diverse as a consequence of intensive artificial selection pressure, free mixing of various breeds, as is often seen in locales where everyone allows their intact dogs to roam freely, results in a couple of generations in dramatically decreased phenotypicall diversity. You take a bunch of individuals from different breeds and in a couple generation you have the prototypical third world feral dog, looking much like a slightly larger version of the coyote. Now, arguably these animals are starting from a different place and subject to far more selection pressure than modern humans, but I think the principle that admixing distinct populations reduces phenotypic diversity by distributing alleles more evenly is sound.
I like this thread, these are things that I though of before… but there are better words in this thread!
It also makes me think of how technology is making the human brain work differently. There was a study done at The Children’s Hospital and Regional Medical Center in Seattle back in 2004 about the causes of ADD and ADHA ("a made up dieses” to most). The study should that children under the age of 3 who watched TV on a regular bases altered the forming of the synapses differently than a child that grow up with out TV during the same age.
They noted that children who didn’t watch TV would stand staring out the window or at an object for many hours at a time. While this was happening the brains where forming synapses that measured distance, movement, concentration and all the other great things about the human brain. The children that where exposed to TV, where of course forming synapses as well, but in those children’s brains where being trained to change ever 30 sec (the average length of a commercial) to 9 minutes (the arrearage length of a show’s viewing time before commercial break).
I am not saying that this is evolution in the works, because it’s not. However, for me it does explain why ADD cases jumped by 300 % during the early 1980’s, and really wasn’t a issue before that, but I do believe that this is an example of how humans are inadvertently causing changes to our own body and mind.
I do wonder though if allot of the mental dieses that are getting more ramped in western society (or seem to be) is because of the technology and comforts that we as human are creating? It it natures way of saying “Well, you Canadian don’t need to be so hairy during winter because of the kick ass jackets you created.... so here have some schizophrenia to balance it out!”
So, I guess the question I am getting at is… With technology getting better, it is now easier for use to change our environment. If evolution is manly controlled by our environment and surroundings, would the technology we create have the side effect of evolution giving some people different abilities to “cope” with the technology? Thus having us humans seeing the evolutionary change, and labelling it as a “mental illness” and us trying to “cure” the evolutionary experiment???
I like this thread, these are things that I though of before… but there are better words in this thread!
It also makes me think of how technology is making the human brain work differently. There was a study done at The Children’s Hospital and Regional Medical Center in Seattle back in 2004 about the causes of ADD and ADHA ("a made up dieses” to most). The study should that children under the age of 3 who watched TV on a regular bases altered the forming of the synapses differently than a child that grow up with out TV during the same age.
They noted that children who didn’t watch TV would stand staring out the window or at an object for many hours at a time. While this was happening the brains where forming synapses that measured distance, movement, concentration and all the other great things about the human brain. The children that where exposed to TV, where of course forming synapses as well, but in those children’s brains where being trained to change ever 30 sec (the average length of a commercial) to 9 minutes (the arrearage length of a show’s viewing time before commercial break).
I am not saying that this is evolution in the works, because it’s not. However, for me it does explain why ADD cases jumped by 300 % during the early 1980’s, and really wasn’t a issue before that, but I do believe that this is an example of how humans are inadvertently causing changes to our own body and mind.
I do wonder though if allot of the mental dieses that are getting more ramped in western society (or seem to be) is because of the technology and comforts that we as human are creating? It it natures way of saying “Well, you Canadian don’t need to be so hairy during winter because of the kick ass jackets you created.... so here have some schizophrenia to balance it out!”
So, I guess the question I am getting at is… With technology getting better, it is now easier for use to change our environment. If evolution is manly controlled by our environment and surroundings, would the technology we create have the side effect of evolution giving some people different abilities to “cope” with the technology? Thus having us humans seeing the evolutionary change, and labelling it as a “mental illness” and us trying to “cure” the evolutionary experiment???
Does any of this make sense? probably not.
I assume you were just anthropomorphizing and you realize that “nature” doesn’t decide anything. Nature doesn’t have a mind or an intelligence. It doesn’t give us one hardship to make up for the loss of a different one.
I think you need to realize how natural selection and evolution work. In order for a trait to become more common ( selected for) it has to increase an individuals ability to reproduce either by increasing that individuals survival ability or making that individual more likely to attract a mate, produce young, or bring those young to reproductive age. Technology may make certain traits more advantageuos to an individual who wants to be succesful in society, but if it doesn’t allow that person to produce more offspring then the trait is not likely to be selected for, and therefor will not cause the species to evolve. ( Good math skills might make you a computer genius, but if it doesn’t help you impregnate lots of women, that particular set of genes will not become more common in society)
Using your example, if technology is somehow increasing the rate of ADD ( and this is clearly conjecture on your part) and ADD made an individual less effective at procuring a mate and reproducing, then individuals who were resistant to the negative effects of technology would be more likely to pass on their genes. Even if that were true though, this technology would have to be present and presenting the same stresses on our decendants for 1000’s of years before it would have a noticable effect on our species.
I like this thread, these are things that I though of before… but there are better words in this thread!
I do wonder though if allot of the mental dieses that are getting more ramped in western society (or seem to be) is because of the technology and comforts that we as human are creating?.
Amos, you’re correct in that the mental illnesses that have become more rampant in western society is a product of our technology, and this is mostly because the newspapers operate on the ‘if it bleeds it leads’ philosophy. In 1900, if a man went crazy in the next state and murdered 5 of his neighbors, it was not something that impacted you directly, unless they were your relatives, or unless there was a manhunt underway, so you would not have heard about it. What has also changed is the societally imposed shame surrounding mental illness has been for the most part lifted. People talk openly about their bouts with mental illness--depression, OCD, you name it. It is no longer seen as a personally moral failing and has come out of the closet. In my own family, I did not know one of my uncles was schizophrenic and had been for about 40 years, until his life was disrupted, he stopped taking his medications and suffered an acute break with reality. It was a huge family secret/shame. Anyone looking a the media would assume that we are more violent than we have ever been in the history of our species, when the opposite is actually true. The media drives the perception. I don’t know enough about ADD and ADHD to address your comments, but as with everything else, I would suspect that a lot of the perceptions about how common these conditions are has a lot to do with media slant.
I’ve often thought that lower intelligence( or at least lower education) is being selected for since those with the least education have the most kids in our society and visa versa, but that assumes that educational level is linked to some genetic trait that can be passed on.
I always thought this to be true. But then I read in Matt Ridley’s Red Queen that it is the rich people who have the most kids. I guess the question is if the richest are the smartest...hmm, are they?
How do scientific advancements in medicine and other fields that are intended to help the weak, ill, disabled, those with unfavorable traits, etc… effect natural selection? If natural selection allows for favorable heritable traits become more common in successive generations, but scientific advancements allow the weak with unfavorable traits to live longer and pass on their genes, how do the two effect each other?
The simple example I’ve thought about is eyeglasses—a lot of people (that I ‘bump’ into) wear eyeglasses. Such people would have had it tough in the past.
The simple example I’ve thought about is eyeglasses—a lot of people (that I ‘bump’ into) wear eyeglasses. Such people would have had it tough in the past.
Yes, but some scientists put forth the theory that ( in some cases)our need for glasses may be caused by our lifestyle rather than a trait that has been allowed to survive.
I’ve often thought that lower intelligence( or at least lower education) is being selected for since those with the least education have the most kids in our society and visa versa, but that assumes that educational level is linked to some genetic trait that can be passed on.
I always thought this to be true. But then I read in Matt Ridley’s Red Queen that it is the rich people who have the most kids. I guess the question is if the richest are the smartest...hmm, are they?
I haven’t read that book, but in most developed countries education is inversely related to the number of children you have. People with college degrees tend to have fewer children than high school drop outs on average.
The simple example I’ve thought about is eyeglasses—a lot of people (that I ‘bump’ into) wear eyeglasses. Such people would have had it tough in the past.
Yes, but some scientists put forth the theory that ( in some cases)our need for glasses may be caused by our lifestyle rather than a trait that has been allowed to survive.
That’s actually a bit of an urban myth for example that too much time reading in the dark, or looking at computer screens can lead to poor vision. Poor distance vision and astigmatisms are simply a factor of the shape of your cornea and that is something you are born with. The need for reading glasses is caused by a loss in the elasticity of the lens over time, and this is strictly a function of age. I am not aware of any lifestyle factors that have been proven to accelerate this process.
