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Is human evolution over?

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  • Registered Users Posts: 391 ✭✭Naz_st


    Would agree though that in human society there are things in it's environment and corresponding human traits that make it both difficult and easy to have offspring?

    I assume that was a question missing a "you" at the beginning? :)

    I think that the answer to that is extremely complex and I don't think it can be clearly linked to a genetic "trait". In Western society circumstance and social convention can make the age at which a relationship is "ready for kids" counter-productive to actually having them. But even in these circumstances there are a whole host of fertility treatments and options available that substantially mitigate the difficulties that arise.


  • Registered Users Posts: 3,809 ✭✭✭CerebralCortex


    Naz_st wrote: »
    I assume that was a question missing a "you" at the beginning? :)

    I think that the answer to that is extremely complex and I don't think it can be clearly linked to a genetic "trait". In Western society circumstance and social convention can make the age at which a relationship is "ready for kids" counter-productive to actually having them. But even in these circumstances there are a whole host of fertility treatments and options available that substantially mitigate the difficulties that arise.

    All of which are a result of human nature and evolution(?)* Important to note that this is the case in Western society.

    *I think Dawkins deals with this idea in The Extended Phenotype. I haven't read it myself but I have read The Selfish Sene which gives a good insight in the process of evolution and natural selection in the last chapter he references The Extended Phenotype.


  • Registered Users Posts: 391 ✭✭Naz_st


    All of which are a result of human nature and evolution(?) Important to note that this is the case in Western society.

    :confused:

    Could you clarify - I'm not getting your point...


  • Registered Users Posts: 3,809 ✭✭✭CerebralCortex


    Naz_st wrote: »
    I assume that was a question missing a "you" at the beginning? :)

    Yes.
    Naz_st wrote: »
    I think that the answer to that is extremely complex and I don't think it can be clearly linked to a genetic "trait". In Western society circumstance and social convention can make the age at which a relationship is "ready for kids" counter-productive to actually having them. But even in these circumstances there are a whole host of fertility treatments and options available that substantially mitigate the difficulties that arise.
    Naz_st wrote: »
    :confused:

    Could you clarify - I'm not getting your point...

    What I mean is, from what I've read(Dawkins and to a lesser extent Dennet) is that the above in bold can be influenced by the gene. Apparently all the individual gene cares about is replication (it doesn't really care it just does replicate). What is good for one genes replication could be disaster for another or a group of genes.


  • Registered Users Posts: 391 ✭✭Naz_st


    What I mean is, from what I've read(Dawkins and to a lesser extent Dennet) is that the above in bold can be influenced by the gene. Apparently all the individual gene cares about is replication (it doesn't really care it just does replicate). What is good for one genes replication could be disaster for another or a group of genes.

    Ok, I think I see where you're coming from now.

    If you are implying that an individual gene is somehow responsible for circumstances related to western societal and religious convention, then I would have to disagree.

    I know Dawkins has argued that behavioural aspects of animals within a society could be linked to genes at some level (he even alludes to this with regard to the independent ubiquity of religion across all societies and throughout history) but the degree to which any human societal or psychological behaviour can be linked to genes is murky at best. And even if certain behaviours can be linked to genes, I think the link between societal convention (as distinct from behavioural aspects of the phenotype) is even more tenuous.

    For example of the difference between the two, I think (AFAIK from one of Dawkins' books, probably the God Delusion) Dawkins suggests that the behavioural trait of being "credulous" has a survival advantage for humans as it enables us to believe unquestioningly what we are told as children by our parents: "don't do X, it's dangerous" will be taken as truth without testing the bounds of how dangerous or why (sort of the genetic opposite of "curiosity killed the cat"!). He goes on to suggest that this "credulity" manifests itself in adults as a lack of defence to the concepts of religion, since any authority figure can substitute the place of parents later on. Now this behaviour (credulity), even if it could be definitively linked to genes, is not the same as the resulting (very diverse) societal conventions that spring from it.

    Also, you should have a look into the concept of "memes", which (as currently theorised) evolve and spread within a society from generation to generation in much the same way as genetic information, but without the necessity of changes in the genotype. Again, I think Dawkins references them in both the Selfish Gene and the God Delusion.

    [Edit: Apparently Dawkins didn't just reference Memes in "The Selfish Gene", he introduced the term! (according to Wikipedia anyway)]


  • Registered Users, Registered Users 2 Posts: 28,789 ✭✭✭✭ScumLord


    Mickeroo wrote: »
    Humans(for the most part) don't adapt to environments,they dig them up,bulldoze them over and build cities on them. We've only adapted to living in comfortable houses. Without a weapon of some sort to protect oursleves most medium to large size animals would make short work of us, and some of the small ones make short work of us as it is. Our abundance and ingenuity is the only advantage we have.
    I don't know about that now, it's true allot in the west have become very lazy but most animals do fear us. If you come across a lion in Africa today its just as afraid of you and will more often than not back down from confrontation with us.

    To say we'd be useless without our weapons is like saying lions would be useless without without their teeth. Weapons have been a part of us even before we where fully human. When you take this into account I'd always bet on the human because we'll always find the right tool for the job. African tribes always killed lions, prehistoric humans brought down mammoths if they where as aggressive as modern elephants that's no small feat.

    We can swim and climb, making us pretty much all terrain. Our heat management is one of the best out there giving us huge advantages over other species.

    In modern times we've really pushed the human body to it's real limits with martial arts and pakour but even without these an ancient human would be a formidable opponent to any animal even on our own (which would rarely happen), your looking at a fairly large animal with two limbs for beating and a knowledge of how to hurt things.


  • Registered Users, Registered Users 2 Posts: 5,888 ✭✭✭AtomicHorror


    Naz_st wrote: »
    But what traits are being "naturally selected" for in our current westernised environment? It seems to me that medical science, technology and population size has significantly hamstrung the process of natural selection...

    Any and all traits leading to death prior to reproduction (be that due to old age or whatever) are being selected against. If death prior to reproduction is happening at all, natural selection is happening.
    Naz_st wrote: »
    Surely environment (and it's stability) is a fundamental catalyst of evolution by natural selection? Otherwise, what is a trait being naturally selected for?

    I mean irrelevant in that it does not have the capacity to halt evolution. Even a perfectly stable environment does prevent the emergence of new traits by mutation. And as long as new traits are emerging, positive or negative selection will occur, regardless of the stability of the environment. Nor does a stable environment eliminate the variation caused by the simple act of reproduction and the resulting recombination of genes. A gene in one combination may be selected for very differently in another combination, irrespective of the stability of the environment.


  • Registered Users Posts: 391 ✭✭Naz_st


    Any and all traits leading to death prior to reproduction (be that due to old age or whatever) are being selected against. If death prior to reproduction is happening at all, natural selection is happening.

    This holds in evolutionary terms only if death prior to reproduction is happening for reasons related to an individuals genes. I mean you can't be genetically pre-disposed to being hit by a bus! :)

    Also, isn't your definition of natural selection is a little too wide for the purposes of evolution as it would seem to include any non-genetic congenital disorders (e.g. spina bifida)?

    But even if you use the absolute terms of natural selection as you have defined it, modern medicine has vastly increased the lifespan (and ergo liklihood of reproduction) for a whole host of specific genetic disorders that would have been naturally selected against in the past (e.g. haemophilia, sickle-cell anaemia, cystic fibrosis).

    Add to that the vastly increased lifespan for the more complex, non-Mendelian genetic disorders that, while not necessary linked to specific genes directly, certain people would seem have a genetic pre-disposition towards (e.g. heart disease, cancer).

    Is this not a strong argument for the current state of medicine and technology homogenising the probability of survival and reproduction to the point of severely stunting the effectiveness of natural selection, and by implication, evolution?
    I mean irrelevant in that it does not have the capacity to halt evolution. Even a perfectly stable environment does prevent the emergence of new traits by mutation. And as long as new traits are emerging, positive or negative selection will occur, regardless of the stability of the environment.

    What about Kettlewell's famous peppered moth experiment - without the instability in the environment (the blackening of the trees around industrialised areas), the "selection" of the black moth would never have occurred.


  • Registered Users, Registered Users 2 Posts: 86,327 ✭✭✭✭Overheal


    ScumLord wrote: »
    But the problem there is when we do go to space we won't be floating around in zero gravity we will find a way of creating gravity.

    Humans are adapting their environment to suit them selfs, more and more the environment is having less of an effect on us. We won't have the need to evolve any changes to survive in space because we'll be cocooned in an environment of our own design.

    The current human body design is one of the best animal bodies that the planet has ever seen IMO. Our abundance is evidence of that.
    Youre assuming we find the way to generate artificial gravity. Or Warp Drive. Or de-pollute the planet, before evolution occurs. As the ozone layer depletes expect human skin to adapt. As pollutants continue filling the air expect our lungs to adapt. We can't spend the rest of our lives in sterile indoor environments - though we can try. Eventually something will give.

    For instance, artificial gravity or not I think you'll find that the human brain develops in leaps and bounds in its capacity for spatial reasoning and the like. How long can it be before mathematics become part of our genetic memory and instinct? How long before we adapt to eating synthetic foods or dietary supplements in lieu of actual food, which is space constraining - we just doing have the cargo space in a deep space ship to stuff 3 square meals a day when we can fit all of the same nutrition into a pill if need be. Electromagnetic Waves? Micro Waves? Radio? Cell Phones? Wi Fi? I can't imagine it has Zero Impact on the human body. The effect may be miniscule and not harmful, but it will still trigger a change in the evolutionary path we take. What says the human body doesnt over thousands of generations learn to listen to, interpret and communicate on these frequencies? Just like insects learned to be thermotropic in order to help them find food sources what says in deep space we dont become naturally sensitive to radio signals to guide us to likely sources of civilization?


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  • Registered Users, Registered Users 2 Posts: 5,888 ✭✭✭AtomicHorror


    Naz_st wrote: »
    This holds in evolutionary terms only if death prior to reproduction is happening for reasons related to an individuals genes. I mean you can't be genetically pre-disposed to being hit by a bus! :)

    Yes you can. Your depth perception is a polygenetic trait, as are your capacities to judge motion, identify patterns (is that a bus?), weigh up risk and even feel fear. When you get hit by a bus, there's a good chance a whole bunch of genes or gene combinations are being selected against.
    Naz_st wrote: »
    Also, isn't your definition of natural selection is a little too wide for the purposes of evolution as it would seem to include any non-genetic congenital disorders (e.g. spina bifida)?

    Spina bifida does seem to have some genetic element, but I take your point. Assuming the reduced likelihood to reproduce or survive contains absolutely no inherited influencing factor then sure, it's not natural selection. But let's face it, there's bound to be some influence on the reproductive rate that comes from something inherited. What if the spina bifida were due to an inheritable aversion to folate intake expressed in the mother? Or what if spina bifida sufferer A has some unrelated genetic traits which make him marginally more likely to reproduce (assuming reproductive function has been preserved) than sufferer B?
    Naz_st wrote: »
    But even if you use the absolute terms of natural selection as you have defined it, modern medicine has vastly increased the lifespan (and ergo liklihood of reproduction) for a whole host of specific genetic disorders that would have been naturally selected against in the past (e.g. haemophilia, sickle-cell anaemia, cystic fibrosis).

    Yes, it has increased the likelihood of reproduction for a great many genes. But it has absolutely not eliminated selection for and against them in various environments. CF sufferers still have an average life span that ranges from 20-40 years, which means that they're undergoing negative selection.
    Naz_st wrote: »
    Add to that the vastly increased lifespan for the more complex, non-Mendelian genetic disorders that, while not necessary linked to specific genes directly, certain people would seem have a genetic pre-disposition towards (e.g. heart disease, cancer).

    Is this not a strong argument for the current state of medicine and technology homogenising the probability of survival and reproduction to the point of severely stunting the effectiveness of natural selection, and by implication, evolution?

    Well that sort of suggests that there is such a thing as "effective natural selection" or "effective evolution". Is that not suggestive of a teleology? If we consider "effective selection" to be the elimination of traits which reduce reproductive success under condition X, then why would we define "effective selection" in the same terms under condition Y? Effective selection or evolution, if such a thing exists, can certainly not be defined in any absolute terms. If our evolution has resulted in us generating a society and environment in which more traits can be reproductively successful than by what criteria can we say that the effectiveness of selection has been reduced? Sure, we can speculate about catastrophic collapses of that society, as much as we could talk about major natural disasters, but those are unknowns. We could no more account for these when under mild selection than we could under strong selection. And indeed it seems intuitive to me that a pool of humans extant in great numbers and expressing a very wide range of genotypes is far better prepared for some hypothetical selective environment than a heavily-pruned population. There are plenty of "detrimental" traits in existence which could suddenly become very beneficial under all manner of circumstances.

    Big digression there. Let's imagine we could homogenise the environment-influenced reproductive rates of all current genotypes. What happens then? For one thing we get genetic drift. The random rise and fall in frequencies of genes based on chance effects in reproduction and not influenced by environment. Genetic drift can result in the loss of genes from the gene pool by chance, which causes evolution. Then there's sexual selection. That gene that doesn't kill you but causes those unsightly ear hairs of yours mean that the boys don't fancy you. Reproductive success is modulated, and we get evolution. And then there's mutagenesis. New mutations arise and become subject to natural selection, sexual selection and genetic drift whilst you try to figure out how to homogenise it relative to other genes.
    What about Kettlewell's famous peppered moth experiment - without the instability in the environment (the blackening of the trees around industrialised areas), the "selection" of the black moth would never have occurred.

    Indeed, what of it? If the environment had not changed there'd have been no need for the selection in the first place. Also, evolution does not always act to change (that will even happen when there's no selection due to drift for example), sometimes it acts to conserve (countering drift).


  • Registered Users Posts: 391 ✭✭Naz_st


    Yes you can. Your depth perception is a polygenetic trait, as are your capacities to judge motion, identify patterns (is that a bus?), weigh up risk and even feel fear. When you get hit by a bus, there's a good chance a whole bunch of genes or gene combinations are being selected against.

    Not if you're looking the other way... :)

    Seriously though, the suggestion that there is an inherent link between the human genotype and being hit by a bus seems an enormously contrived and speculative connection to me.
    Spina bifida does seem to have some genetic element, but I take your point. Assuming the reduced likelihood to reproduce or survive contains absolutely no inherited influencing factor then sure, it's not natural selection. But let's face it, there's bound to be some influence on the reproductive rate that comes from something inherited. What if the spina bifida were due to an inheritable aversion to folate intake expressed in the mother? Or what if spina bifida sufferer A has some unrelated genetic traits which make him marginally more likely to reproduce (assuming reproductive function has been preserved) than sufferer B?

    What if this, what if that. Doesn't sound very scientific to me...
    Yes, it has increased the likelihood of reproduction for a great many genes. But it has absolutely not eliminated selection for and against them in various environments. CF sufferers still have an average life span that ranges from 20-40 years, which means that they're undergoing negative selection.

    The average lifespan of a human for almost the entirety of the history of our species has been a lot less than 40 years. But anyway, my point wasn't that natural selection has been completely stopped, more that it has been significantly impaired in the current modern environment.
    If our evolution has resulted in us generating a society and environment in which more traits can be reproductively successful than by what criteria can we say that the effectiveness of selection has been reduced? Sure, we can speculate about catastrophic collapses of that society, as much as we could talk about major natural disasters, but those are unknowns. We could no more account for these when under mild selection than we could under strong selection. And indeed it seems intuitive to me that a pool of humans extant in great numbers and expressing a very wide range of genotypes is far better prepared for some hypothetical selective environment than a heavily-pruned population. There are plenty of "detrimental" traits in existence which could suddenly become very beneficial under all manner of circumstances.

    Isn't that my point? That the current large population, coupled with diverse genotypes with a stable environment, medically advanced technology and knowledge, and non-evolution oriented social conventions have left us in a evolutionary equilibrium that awaits environmental disruption to initiate the next evolutionary step.
    Big digression there. Let's imagine we could homogenise the environment-influenced reproductive rates of all current genotypes. What happens then? For one thing we get genetic drift. The random rise and fall in frequencies of genes based on chance effects in reproduction and not influenced by environment. Genetic drift can result in the loss of genes from the gene pool by chance, which causes evolution.

    Hmmm... might have to give you that one. :)

    But I would suggest that the degree to which genetic drift (and the subsequent random, unselected for genetic changes) is a major contributory factor in Darwinian evolutionary theory is not obvious? (but I don't know enough about it to do more than pose the question...)
    Then there's sexual selection. That gene that doesn't kill you but causes those unsightly ear hairs of yours mean that the boys don't fancy you. Reproductive success is modulated, and we get evolution.

    As per my original post, ugliness is not a very good argument for negative selection in such a large and geographically unimpeded species. There's someone for everyone... (thankfully!)
    And then there's mutagenesis. New mutations arise and become subject to natural selection, sexual selection and genetic drift whilst you try to figure out how to homogenise it relative to other genes.

    They only become subject to natural selection if they are inheritable variations that improve the chances of survival and reproduction. My main point is that that is a tall order in current modern environment.
    Indeed, what of it? If the environment had not changed there'd have been no need for the selection in the first place. Also, evolution does not always act to change (that will even happen when there's no selection due to drift for example), sometimes it acts to conserve (countering drift).


    "Indeed, what of it?" => "If the environment had not changed there'd have been no need for the selection in the first place."

    Exactly.

    I was just pointing out that instability of environment is an intrinsic and fundamental catalyst to evolution and that, by inference, stability of environment is an intrinsic inhibitor to evolution. I mean the lack of stable environments has played a major role in the evolution or our own species on numerous critical occasions. For ~150 million years over the Jurassic and cretaceous periods, the earth was a stable environment with dinosaurs being the most dominant and abundant land vertebrate. If the environment had remained stable, we wouldn't be here. It is only the instability in the environment caused by the K-T extinction event that allowed our small insectivore ancestors to increase rapidly in size and diversity. That is just one example, the oxygenation of the atmosphere around 2.5 billion years ago is another, probably the most important environmental disruption in the history of the evolution of most of the species of multi-cellular life on the planet.

    Environmental stability as an inhibitor to evolution is probably most evident if you look at the work of genetic algorithms (it's much easier to see evolutionary change when you can speed up the process into a matter of minutes!). When a genetic algorithm is used to find a best fit to a particular problem (environment), there often comes a point at which no further genetic changes are made in subsequent generations as the "fitness" of the solution has reached a plateau and doesn't increase, i.e. the solution cannot adapt any further to its environment. Interestingly (and I use that term in its nerdiest sense!), this does not necessarily mean that the algorithm has found the best solution, just the best solution that arises from the evolutionary path taken. Other solutions may exist down different paths that may be better than this one, but the steps to that solution from the current one are not possible under the guidance of the selection parameters used, much in the same way that the tree hierarchy of natural life exhibits multiple different distinct evolutions for the same components (eyes, wings, etc). But the point is that stable equilibrium does occur.
    A neat example of genetic algorithms at work on recognisable problems are the evolved creatures examples. One of the originals, but still one of the best presented:


    Basically, I just don't see how you can suggest that stability of environment isn't an antagonist to the evolutionary process?


  • Closed Accounts Posts: 5,064 ✭✭✭Gurgle


    I'd guess that evolution in western society will favour a tendency to hit puberty earlier and menopause later.

    Most of the 'survival' evolution is pretty much stopped with modern medicine - short of a major genetic problem we can all expect to live natural lives long enough to breed.


  • Registered Users, Registered Users 2 Posts: 5,888 ✭✭✭AtomicHorror


    Gurgle wrote: »
    Most of the 'survival' evolution is pretty much stopped with modern medicine - short of a major genetic problem we can all expect to live natural lives long enough to breed.

    Nas made a similar point. If we all survive to breed that does not mean we are escaping selection. It's the rate that matters in evolutionary terms. So if we can all live to be the same age, that still doesn't mean we're all equally reproductively successful. Differential rates of reproductive success, whether that involves death or not means selection is happening. As long as we're not all having the same numbers of children, the rates are differential and that will be influenced by inheritable traits.

    Aside from this, too much to respond to and I just don't have the time so I'll address one other point.
    Naz_st wrote: »
    Basically, I just don't see how you can suggest that stability of environment isn't an antagonist to the evolutionary process?

    To skip to the punchline:

    "Because evolution has no goal." For it to be antagonised it has to be going somewhere, but it isn't. Selection is being antagonised by modern medicine to an extent and only with respect to certain traits, evolution can't be antagonised unless you're just not a replicator.


  • Registered Users Posts: 391 ✭✭Naz_st


    To skip to the punchline:

    "Because evolution has no goal." For it to be antagonised it has to be going somewhere, but it isn't.

    Ah, c'mon, the anthropomorphic goal was directly implied by the OPs question! In order to answer it all, one has to assume this implied goal (as we both have been up until now). The time for that point was your first post, it would have made for a short thread though! :)

    Also, plenty of intrinsically goalless systems have individual goals for components of the system (e.g. a stock market has no goal in and of itself, but the stock brokers who make up the stock market certainly do have goals!)
    Selection is being antagonised by modern medicine to an extent and only with respect to certain traits, evolution can't be antagonised unless you're just not a replicator.

    Well then, let's just leave it that we agree that natural selection is being curtailed by the modern environment (perhaps not completely on the degree). Personally, I think that means that evolution (as goal-oriented by the question asked) is definitionally curtailed too, but I'll shut up about it now!


  • Registered Users, Registered Users 2 Posts: 5,888 ✭✭✭AtomicHorror


    Naz_st wrote: »
    Ah, c'mon, the anthropomorphic goal was directly implied by the OPs question! In order to answer it all, one has to assume this implied goal (as we both have been up until now). The time for that point was your first post, it would have made for a short thread though! :)

    If it was implied, I didn't pick up on it initially. My other points were valid anyway.
    Naz_st wrote: »
    Also, plenty of intrinsically goalless systems have individual goals for components of the system (e.g. a stock market has no goal in and of itself, but the stock brokers who make up the stock market certainly do have goals!)

    What elements of evolution have a goal? The products of evolution have goals, but the process itself does not.
    Naz_st wrote: »
    Well then, let's just leave it that we agree that natural selection is being curtailed by the modern environment (perhaps not completely on the degree). Personally, I think that means that evolution (as goal-oriented by the question asked) is definitionally curtailed too, but I'll shut up about it now!

    Perhaps this is more of a semantic thing. You seem to equate evolution with "change". Whereas I view evolution in broader terms with variation being one outcome of that process.


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  • Closed Accounts Posts: 2,736 ✭✭✭tech77


    God, I hate such pompous, arrogant reasoning.
    It boils down to this:

    Mutation + Natural Selection = Evolution

    Neither of these has stopped, or ever will stop, as long as a living carbon molecule exists.

    End of story.


    Yeah, i can't stand the pomposity and hubris that humans have about this.

    Perfection my ar$e- there's infinite room for improvement.


  • Registered Users, Registered Users 2 Posts: 5,949 ✭✭✭A Primal Nut


    All speculation of course...

    Hopefully we will evolve so our eyesight will become resistant to staring at a computer for half a day. Might take a while though.

    I could see the skills used to drive and concentrate while driving probably improving over a long period of time.

    Resistance to AIDS in another big thing.

    I remember watching a documentary which suggested that a gene which makes us better adapted to urban living (as supposed to the groups of 100 we evolved to live around, again according to the documentary) is spreading throughout the population. No idea if thats true or not.

    One big possibility I think there are less and less health reasons for women not to be able to have kids at higher ages, with the way the weak are protected now. Perhaps, the age at which they can have kids will increase, and ultimately people will live longer. Bare in mind that nobody who lived through all the recent medical developments has got a chance to break the oldest person record. I think Genetics could extend it also. In addition, again because the weak are protected, people will be able to have more kids with more different partners. Perhaps monogomy will die out?

    We will get taller but only until we reach an optimum.

    We'll probably get better looking, particular men, because women can choose based on looks a lot more than in the past when their main concern was someone who could provide for them. Maybe obesity will get much less common, or at least the genes that help to cause it.


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