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Medical Forum / General / General / July 2006Can current environment effect "natural selection"?
Hello, "Natural selection is somewhat defined as a natural process resulting in the evolution of organisms best adapted to the environment or processes by which some individual organisms survive and reproduce at greater or lesser rates, within a particular ecosystem. The process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated. Natural selection works on the whole individual, but only the heritable component of a trait will be passed on to the offspring, with the result that favorable, heritable traits become more common in the next generation. Given enough time, this passive process can result in adaptations and speciation.Natural selection acts on the phenotype. The phenotype is the overall result of an individual's genetic make-up (genotype), the environment, and the interactions between genes and between genes and the environment. Often, natural selection acts on specific traits of an individual, and the terms phenotype and genotype are sometimes used narrowly to indicate these specific traits. The key element in understanding natural selection is the concept of fitness or predominance of "survival of fittest". It is also useful to make a mechanistic distinction between ecological selection and sexual selection. Ecological selection covers any mechanism of selection as a result of the environment (including relatives (e.g. kin selection) and conspecifics (e.g. competition, infanticide)), while sexual selection refers specifically to competition between conspecifics for mates. Sexual selection includes mechanisms such as mate choice and male-male competition although the two forms can act in combination in some species, when females choose the winners of the male-male competition. Mate choice, or intersexual selection, typically involves female choice, as it is usually the females who are most choosy, but in some sex-role reversed species it is the males that choose. http://en.wikipedia.org/wiki/Natural_selection " ""The effect of natural selection can be one of three types: Directional selection: in directional selection the shift in allele frequencies occurs in a consistent direction. The classic example of this is the peppered moth. The moths come in a dark and light variety. Before the industrial revolution the light variety predominated...... Stabilizing selection: in this case, selection against extremes stabilizes a population with an intermediate phenotype. Destabilizing selection: contrastingly, selection can disfavor an intermediate phenotype, stabilizing a population with two extreme phenotypes. http://mywebpages.comcast.net/biologycentury/pages/microevol3.html "" ......................... In this respect I have few questions/thoughts:- 1. Can current/modern environment and lifestyle effect natural process of "natural selection"? 1. Whether "natural selection" process recognize current environment esp. prevailing in big cities similarily as natural environment and can act naturally? 2. Do we still have genetic material free from predisposed/inherited diseases and disorders? 3. Whether "getting more predisposed/inherited diseases or disorders" is an indicator of deviation from "natural selection" and of "survival of fittest"? Best wishes. > In this respect I have few questions/thoughts:- > > 1. Can current/modern environment and lifestyle effect natural process > of "natural selection"? Modern technology most certantly has changed the forces of natural selection. For example, modern medicine has eliminated many of the diseases which used to kill off millions. You can look at the human genome and you'll find mutations that help protect us against diseases such as malaria, cholera, etc. Today, at least in developed nation, selection for these resistance genes no longer exists. The same could be said about mutations which are otherwise bad - PKU gene for example. In fact, some people argue that humans are no longer evolving as our technology has overcome all selection. Except, perhaps, the selection against the most deleterious mutations. Personally speaking, I would argue that the above concept is flawed at a fundamental level - although human technology has most certantly altered selection, it still exists. People often forget that selection doesn't just mean killing off those who aren't well evolved, but also can drive the successful breeding of those who are well evolved. And in modern society we do see differences in the birth rates among people of certain social demographics... > 1. Whether "natural selection" process recognize current environment > esp. prevailing in big cities similarily as natural environment and can > act naturally? Natural selection just means selection driven by the environment. A city is nothing more then another environment, and certantly can impact on selection. For example, people who are more resistant to the effects of pollution, or the diseases which are common in crowded locations, would do well in a city compared to people without these traits. > 2. Do we still have genetic material free from predisposed/inherited > diseases and disorders? All kinds. Over half of your DNA is what scientists call "junk" DNA. Although this DNA is not without a role, it does not code for genes. As such, it is generally considered not to be involved in evolution. Likewise, there are genes which are essentially "shielded" from being involved in diseases. This can occur for a variety of reasons - be it redundancy (i.e. other genes can do the job of the gene in question), or the gene being absolutely required for life (i.e. mutations in it = death). > 3. Whether "getting more predisposed/inherited diseases or disorders" > is an indicator of deviation from "natural selection" and of "survival > of fittest"? Highly unlikely. Firstly, the rates of human evolution are relatively slow, so modern technology simply hasn't been around long enough to have a huge impact in the variation found within the human genome. Secondly, many of the genetic and partially genetic diseases we suffer from today have existed for a long time - descriptions of people with heart disease and diabetes go back as far as ancient Egypt. Lastly, in many cases the gene(s) which impart susceptibility to some diseases actually evolved to protect us from pathogens. For example, the genes which lead to sycle-cell-cell anemia and cystic fibrosis evolved to protect us against malaria and cholera respectively. Likewise, there is some weak evidence that some of the genes which predispose us to diabetes may have evolved to increase our bodies ability to detect some viral pathogens. As such, these genes would be quite old; in some cases old enough that we find similar mutations in our close relatives, such as chimps. Bryan Kumar, I cam across this on-line presentation which talks directly about natural selection in humans. It'll probably answer most of your questions. I think it is free. http://www.sciencemag.org/multimedia/video/seminars/ Bryan > > In this respect I have few questions/thoughts:- > > [quoted text clipped - 20 lines] > society we do see differences in the birth rates among people of certain > social demographics... Is it so that many diseases, currently developed at epidemeic level as diabetes2, hypertention, cancer etc. may not be there in future due to new treatments? Can't we be naturally evolved to resistance to diseases persisted since long as malaria? How can it be for sure that we made it? Furthur, can't non-exposure or lesser exposure to persisting diseases since long(may also come later) reverse our evolved resistances and tolerances to these diseases on natural selection? > > 1. Whether "natural selection" process recognize current environment > > esp. prevailing in big cities similarily as natural environment and can [quoted text clipped - 5 lines] > of pollution, or the diseases which are common in crowded locations, > would do well in a city compared to people without these traits. Yes, who can be in better natural/real health, more resistent/tollerant or lesser one? Btw, whether a more resistant/tollerant person move to healthful natural environment, can it effect him adversely? > > 2. Do we still have genetic material free from predisposed/inherited > > diseases and disorders? [quoted text clipped - 6 lines] > redundancy (i.e. other genes can do the job of the gene in question), or > the gene being absolutely required for life (i.e. mutations in it = death). How these can be expressed if we reverse current environment to natural environment? Can we still aquire purest form of genetic material(somewhat like do interpreted as adam and eve)? > > 3. Whether "getting more predisposed/inherited diseases or disorders" > > is an indicator of deviation from "natural selection" and of "survival [quoted text clipped - 16 lines] > > Bryan Disease might have existed since long back(may be type1diabetes only) in somewhat dormant stages, but how is is now showing epidemic type spread? Modern lifestyle is ofter blaimen for this type of spread. If rates of human evolution are relatively slow how can we expect that current environment or current interventions(which are relatively new) can effect our genetic material, causes resistences etc.? Two thoughts are appeared by this discussions:- 1. Can short period of modernization effect our genetic material and natural selection? 2. Are we encouraging reversal of evolved resistences/tollerances due to unnatural interventions of treatments? Making a person healthy by interventions may pass signals to natural selection that problem don't exist so select those without resistent to these problems. Right? > > > In this respect I have few questions/thoughts:- > > > [quoted text clipped - 101 lines] > interventions may pass signals to natural selection that problem don't > exist so select those without resistent to these problems. Right? Let us take case of diabetes. If we are suffering and taking insulin, how natural selection can adjust diabetes in next generations? If modern introductions are continuing at increasing rates but side by side modern interventions are also increasing, how "natural selection" will adjust those moden introductions? >>>In this respect I have few questions/thoughts:- >>> [quoted text clipped - 24 lines] > diabetes2, hypertention, cancer etc. may not be there in future due to > new treatments? Hopefully. Some of these diseases, like cancer, are an inevitable result of our biology. So people will always get them, but we'll hopefully be able to cure or treat the disease. In the case of diabetes, one day we may be able to vaccinate against it. Others, like hypertension, need not exist today. Exercise and proper diet could wipe that out today... > Can't we be naturally evolved to resistance to diseases persisted since > long as malaria? How can it be for sure that we made it? Some people have evolved resistance to malaria. Sycle-cell anemia represents one such advance. If you have one copy of the sycle-cell gene you're as close to immune to malaria as you can get. However, if you get two copies of that gene you get sycle-cell disease. There are many other mutations which have induced resistance to malaria; some are totally harmless to humans if they get it in 2 copies. As for how we know if a gene provides resistance, it's simple. You look for people who are resistant to a disease (say people who make it through a large outbreak without getting disease) and then use conventional genetic mapping techniques to identify genes which are associated with surviving the disease. Given enough time, and enough people getting sick, you can identify the resistance gene(s). > Furthur, can't non-exposure or lesser exposure to persisting diseases > since long(may also come later) reverse our evolved resistances and > tolerances to these diseases on natural selection? Yes. If you are not exposed to a pathogen we've evolved resistance to can lead, over many generations, to a loss of that gene. The reason being that there is no longer disease selecting for the gene, so there is nothing to keep in in the population. If the gene also has deleterious effects, the gene may even be "forced" out of the population by natural selection. >>>2. Do we still have genetic material free from predisposed/inherited >>>diseases and disorders? [quoted text clipped - 9 lines] > How these can be expressed if we reverse current environment to natural > environment? They're not expressed, ever. Junk DNA just sites around, and doesn't encode for any genes. > Can we still aquire purest form of genetic material(somewhat like do > interpreted as adam and eve)? Not really. At times genes or chunks of DNA will get duplicated during cell division. This can make copies of a gene which can then evolve into something else. But we do not receive "new" DNA from outside our bodies - all we get is what mom & dad give to us. Bacteria are an example of the opposite. Many bacteria can import new DNA from other bacteria, thus giving themselves "new" genes which come from other species. > Disease might have existed since long back(may be type1diabetes only) > in somewhat dormant stages, but how is is now showing epidemic type > spread? Modern lifestyle is ofter blaimen for this type of spread. A lot of the diseases we suffer from now (diabetes being a good example) have existed for a long time. They simply were very rare until recently as people did not live long enough for them to form, and didn't have the lifestyle to increase the risk to the levels we have now. So our longer lives are one of the reasons these diseases are more common, and the other half of the equation is they way we live now (notably diet). But the underlying genetics have been around for thousands, if not hundreds of thousands or millions, of years. > If rates of human evolution are relatively slow how can we expect that > current environment or current interventions(which are relatively new) > can effect our genetic material, causes resistences etc.? In our lifetimes, not much. It takes hundreds or more generations to see significant genetic change, so modern technology isn't likely to have genetic consequences for a long time yet. The obvious exception being genetic engineering. That allows for instantaneous change... > Two thoughts are appeared by this discussions:- > > 1. Can short period of modernization effect our genetic material and > natural selection? No for genetic material, yes for natural selection. Exception to the 'no' being genetic engineering. > 2. Are we encouraging reversal of evolved resistences/tollerances due > to unnatural interventions of treatments? Highly unlikely. Also, there is no such thing as "reverse evolution". Evolution only goes forward, and if our current technology is driving evolution "backwards" - meaning that we're loosing previous adaption, then we're loosing those adaptations as it is an advantage to us. > Making a person healthy by > interventions may pass signals to natural selection that problem don't > exist so select those without resistent to these problems. Right? Yes. Bryan > >>>In this respect I have few questions/thoughts:- > >>> [quoted text clipped - 31 lines] > hypertension, need not exist today. Exercise and proper diet could wipe > that out today... Yes, can it be thought that diabetes2 is a predisposition or greed to overeating and living sed. lifestyle? Till we actually lose normal production of insulin, or till we become alike type1 or till we start losing weight, we may control BG levels by diet and excercise. But it may not be in our normal control. Why then we don't give such medicines which resist us to overeat or encourage us to do physical activities? > > Can't we be naturally evolved to resistance to diseases persisted since > > long as malaria? How can it be for sure that we made it? [quoted text clipped - 5 lines] > many other mutations which have induced resistance to malaria; some are > totally harmless to humans if they get it in 2 copies. Is it at the cost of getting bigger disease? I think it is not normally evolved resistance or due natural selection? Btw malaria or few other regular infections can also be due to some biochemic imbalances/accumulations and may be meant to balance those..as NaCl? Can we get these balances and feel better after restore health. Getting resistances on natural selection due to exposure of these, may be other favour to our offsprings. > As for how we know if a gene provides resistance, it's simple. You look > for people who are resistant to a disease (say people who make it > through a large outbreak without getting disease) and then use > conventional genetic mapping techniques to identify genes which are > associated with surviving the disease. Given enough time, and enough > people getting sick, you can identify the resistance gene(s). How we will get such resistances if we shall be immediately and regularily treated midway of getting natural selection prepared for it? > > Furthur, can't non-exposure or lesser exposure to persisting diseases > > since long(may also come later) reverse our evolved resistances and [quoted text clipped - 6 lines] > deleterious effects, the gene may even be "forced" out of the population > by natural selection. Why many generations? Can't it happen in next genaration by "natural selection" route? > >>>2. Do we still have genetic material free from predisposed/inherited > >>>diseases and disorders? [quoted text clipped - 12 lines] > They're not expressed, ever. Junk DNA just sites around, and doesn't > encode for any genes. Other genes? > > Can we still aquire purest form of genetic material(somewhat like do > > interpreted as adam and eve)? [quoted text clipped - 3 lines] > into something else. But we do not receive "new" DNA from outside our > bodies - all we get is what mom & dad give to us. Means all of our genetic material already become polluted to current and past environmental effects? How reversal of past and present environmental effects mutated in our genes can take place on reversal of environment? > Bacteria are an example of the opposite. Many bacteria can import new > DNA from other bacteria, thus giving themselves "new" genes which come > from other species. Can it reverse evolved resistances gained by them? Whether resistances of bacterais can be reversible considering their shrt life? Why we don't try it? > > Disease might have existed since long back(may be type1diabetes only) > > in somewhat dormant stages, but how is is now showing epidemic type [quoted text clipped - 8 lines] > the underlying genetics have been around for thousands, if not hundreds > of thousands or millions, of years. We may need greed of food so been evolved previously. It can be a normal evolution. But current environment can be responsible to use such evolved property excessively? When we go to some remote natural area even for short period, sometime such greed or excessive cravings or effect of overeating don't truble to diabetes. How? > > If rates of human evolution are relatively slow how can we expect that > > current environment or current interventions(which are relatively new) [quoted text clipped - 3 lines] > see significant genetic change, so modern technology isn't likely to > have genetic consequences for a long time yet. Can't it be possible via "natural selection" route? > The obvious exception being genetic engineering. That allows for > instantaneous change... [quoted text clipped - 6 lines] > No for genetic material, yes for natural selection. Exception to the > 'no' being genetic engineering. Ok, can modern introductions make our offspring resistance to their adverse effects via "natural selection" route? Will natural selection recognize and process such adversities in view of that these introductions are not very old? > > 2. Are we encouraging reversal of evolved resistences/tollerances due > > to unnatural interventions of treatments? [quoted text clipped - 3 lines] > evolution "backwards" - meaning that we're loosing previous adaption, > then we're loosing those adaptations as it is an advantage to us. Natural selection process behave according to exposed environment to people. If there is no impression of diseases due to modern introductions because instantly and regularily treated by modern interventions, how natural selection can process modern introductions? > > Making a person healthy by > > interventions may pass signals to natural selection that problem don't > > exist so select those without resistent to these problems. Right? > > Yes. Does it not make our offsprings to lose such possible resistances to survive naturally under modern environment? Thanks and regards. >Hopefully. Some of these diseases, like cancer, are an inevitable >result of our biology. So people will always get them, but we'll >hopefully be able to cure or treat the disease. In the case of >diabetes, one day we may be able to vaccinate against it. Others, like >hypertension, need not exist today. Exercise and proper diet could wipe >that out today... Some of it. Not necessarily all of it. -- David Wright :: alphabeta at prodigy.net These are my opinions only, but they're almost always correct. "If you can't say something nice, then sit next to me." -- Alice Roosevelt Longworth Via natural selection route or via inheritance, one side can be the getting the resistances, tolerances or immunities and improvements in these AND other other side be getting or worsening of predisositions, inherited diseases, weakened immunities etc. How modern introductions with or without moden interventions can effect above? > Via natural selection route or via inheritance, one side can be the > getting the resistances, tolerances or immunities and improvements in [quoted text clipped - 3 lines] > How modern introductions with or without moden interventions can effect > above? I personally would argue that medical intervention in cases of infectious disease are taking selective pressure off of our immune systems. Plenty of people ought to have died from bacterial infections who got antibiotics, plenty of people who would have died from viruses have been treated with measures that allow them to overcome. Each of these people who breed weaken the gene pool in terms of improving the gene pool when it comes to the question of immunity. Keep in mind though that I probably would have died a few times over already as a result of bacterial infections, so I tend to side with intervention. Nature will still send out plagues and pestilence which despite the best intentions cannot be prepared for. > > Via natural selection route or via inheritance, one side can be the > > getting the resistances, tolerances or immunities and improvements in [quoted text clipped - 18 lines] > intervention. Nature will still send out plagues and pestilence which > despite the best intentions cannot be prepared for. Yes, that is for us, what about its impact on our next generations? Should we not try some other means, if possible, which neither effect our immunity nor natural selections's natural process. Probably we could have got "resistent childern" to all or most current diseases. How can it be possible that, our system get required exposure to modern introductions alongwith we are also saved? >>>Via natural selection route or via inheritance, one side can be the >>>getting the resistances, tolerances or immunities and improvements in [quoted text clipped - 26 lines] > How can it be possible that, our system get required exposure to modern > introductions alongwith we are also saved? The point of natural selection is that some people have to die.. or better said, some people arent able to reproduce. The only way to keep the selective pressure on would be to decide whether or not a person would have died without medical intervention, then sterilize them if they would have died. In this way you get to live a good life sans reproduction, and our immune system continues to adapt appropriately. I have a strong feeling that no one would ever support such methods, and I for one would never willingly allow someone to sterilize me. > >>>Via natural selection route or via inheritance, one side can be the > >>>getting the resistances, tolerances or immunities and improvements in [quoted text clipped - 38 lines] > I have a strong feeling that no one would ever support such methods, and > I for one would never willingly allow someone to sterilize me. Can't we be precautionary and selective about modern strong interventions till we plan to reproduce or reproduce early or follow some mild natural therapies etc. Probably, we don't know, where we are in "natural selection" and if our childern will be fittest or not? We have to be survived, fittest or not, children fittest or not, is bit impractical currently. Anywat to move furthur; Sirvival of fittest may be dependent on motility and heath of sperms..who can run fastest and reach eariest ,may be fittest. Vitality, survival and motility of sperms may be effected by prevailent environment of male/female reproductive tracts. So; 1. Whether motility can be related to fittest sperm? 2. Which can run fast X or Y ? 3. Can environment of male/female reproductive tract impact on getting fittest sperm? 4. Can currentmodern environment effect reproductive tract's environment resulting into different "natural selection? 5. Who is resonsible or more responsible for variations in natural selections--male or female? "The experiment pitted a strain of yeast that reproduces sexually against a modified, asexual version of the same strain. Each grew and reproduced at the same rate, said Matthew Goddard of the University of Auckland. Then Goddard and his colleagues raised the stakes, providing less food to the little critters. Under these conditions, those engaging in the ultimate act still managed a growth rate of 94 percent whereas the asexual strain only reached 80 percent. Sexual organisms seem fit to survive. The research is detailed in the March 31 issue of Nature http://www.livescience.com/humanbiology/050330_sex_good.html " How outer environment and in reproductive tracts, emotions etc. can effect "natural selection"? Can more numbers of sperms be related to get more available material for better NS in view of we got more variations in environments? Can there be some morphological and chemical changes in reproductive tract/organs to carry on "natural selection" process as per need of time? Finally, Do we have different type of sperms with different genetic make ups in one human on spermagenesis? Can't natural selection and predispositions be dependent on environment--outer or in reproductive tracts OR predispositionson post fertilization during pregnancy or on prevailing atmosphere at birth and finally on post birth exposures? >> Via natural selection route or via inheritance, one side can be the >> getting the resistances, tolerances or immunities and improvements in [quoted text clipped - 6 lines] >I personally would argue that medical intervention in cases of >infectious disease are taking selective pressure off of our immune systems. Maybe, but it's really too random to say what effect that's having. >Plenty of people ought to have died from bacterial infections who got >antibiotics, plenty of people who would have died from viruses have been >treated with measures that allow them to overcome. Which says there'd be fewer people alive today, but you don't know the net effect of that. What if people who are terrific at fighting off infection also tended to be really stupid? That wouldn't provide a net advantage, necessarily. >Each of these people who breed weaken the gene pool in terms of >improving the gene pool when it comes to the question of immunity. That's too vague. You can't be sure. >Keep in mind though that I probably would have died a few times over >already as a result of bacterial infections, so I tend to side with >intervention. Nature will still send out plagues and pestilence which >despite the best intentions cannot be prepared for. And whether or not we had ancestors who were good at fighting off, say, bacterial infections. -- David Wright :: alphabeta at prodigy.net These are my opinions only, but they're almost always correct. "If you can't say something nice, then sit next to me." -- Alice Roosevelt Longworth >>>Via natural selection route or via inheritance, one side can be the >>>getting the resistances, tolerances or immunities and improvements in [quoted text clipped - 8 lines] > > Maybe, but it's really too random to say what effect that's having. Not really, it is having the effect of promoting the reproduction of people who would naturally succumb to infectious diseases prior to sexual maturity. Thereby keeping genetics which would otherwise be eliminated in the gene pool. >>Plenty of people ought to have died from bacterial infections who got >>antibiotics, plenty of people who would have died from viruses have been [quoted text clipped - 4 lines] > infection also tended to be really stupid? That wouldn't provide a > net advantage, necessarily. Actually, in a system where natural selection is king, intelligence has as much to do with fitness as a good immune system, often less. Don't make the elitist assumption that intelligence is the key to survival, single celled bacteria evetually kill old smart mammals on a regular basis. >>Each of these people who breed weaken the gene pool in terms of >>improving the gene pool when it comes to the question of immunity. > > That's too vague. You can't be sure. The only reason you cant be 100% sure is that we don't get to know what it's like where the opposite is true. Oddly enough, in places where modern medicine is not as prevalent, people with immunity to AIDS are starting to show up. Is this a coincidence, or did a lot of people have to die for an evolved immune system to show itself? The abhorrence of death is a value judgement. In the perspective of evolution, death is not a bad thing. >>Keep in mind though that I probably would have died a few times over >>already as a result of bacterial infections, so I tend to side with [quoted text clipped - 3 lines] > And whether or not we had ancestors who were good at fighting off, > say, bacterial infections. My point exactly. To illustrate further. Lets say that tommorow, a new bacterial pathogen evolves, to which no one has complete immunity, and there are no effective antibiotics. Lets say in the population, there are people who can survive the infection, but become blind as a result. Eventually, we would have the situation of every member of the population being immune, as all the totally susceptible people would have died off. Sadly we'd also have a lot of blind people. What we are doing by avoiding natural selection is building up a large population with inadequate genetic fitness. Whether we can eternally support this choice or not remains to be seen. If not, there probably will be a time when it all comes crashing down, a natural population correction if you will. Which sounds suspiciously like the language used to describe global flu pandemics. |
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