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Earth Science

Humans Evolving Faster Than Ever 253

Kwyj1b0 writes "In a massive study on genetic variation among humans, researchers found that most changes have occurred in the last 200 generations, too fast for natural selection to catch up. Recent papers show that rare genetic variations have a more drastic effect than previously believed. Another result shows that 'we carry a much larger load of deleterious variants' (as well as positive variants) than our ancestors 200 generations ago."
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Humans Evolving Faster Than Ever

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  • by Ubi_NL ( 313657 ) <.joris. .at. .ideeel.nl.> on Saturday December 01, 2012 @04:12AM (#42153003) Journal

    Acquisition of mutations is not evolution. Evolution is the combination of variations AND selection of those traits that increase fitness. The fact that we only acquire more genetic mutations means that selectionhas gone down and evolution with it. The simple explanation is that healt care enabled us to cheat on selection.

    • Re: (Score:3, Interesting)

      by Ubi_NL ( 313657 )

      I should add that selection based on culture (love, pre-arranged weddings etc) rather than fitness also does not help evolution.

      • by Fallingcow ( 213461 ) on Saturday December 01, 2012 @04:46AM (#42153113) Homepage

        What does "help" mean, in an evolutionary context?

        Seems to me that culture is just another factor to which an organism may, over generations, adapt.

        • Re: (Score:2, Interesting)

          by Ubi_NL ( 313657 )

          So is fabrication of fire arms, but both are not evolution in theway we have defined the term evolution.

          • by Hognoxious ( 631665 ) on Saturday December 01, 2012 @06:16AM (#42153407) Homepage Journal

            Evolution can occur on things that aren't coded in DNA. Software, for example.

            Dawkins, memes. Does that ring a bell?

          • by Kjella ( 173770 ) on Saturday December 01, 2012 @09:12AM (#42153949) Homepage

            So is fabrication of fire arms, but both are not evolution in theway we have defined the term evolution.

            Well you're right in that if we saw people with machine guns slaughter guys with muskets, we wouldn't call that evolution. Neither is going from 6-7 children/woman to 2-3 children/woman as many countries have done in a generation or two. It's only evolution if there's a reasonably clear link between your genetic makeup and your ability/probability to reproduce. I don't see much chance that a random mutation would help me survive a bullet, though there's a good chance that personality traits that are genetic could help me avoid a situation (or worse, put me in a situation) where I get shot. That's real evolutionary pressure right there, though I think the number of people shot and killed is too small to have any real significance.

            But in terms of culture then genetics is a huge part of attractiveness, including appearance, personality and intelligence. That can have both direct effects to hooking up and indirect effects like social circle, social status and economic status. And perhaps even far more so today, how many kids you want to have. Sure society is a huge influence here but ultimately it comes down to personal choice that may be a lot more built in than people realize. Changing culture also makes different genes important, in a society with pre-arranged marriages your courtship genes might not matter much but in a society of free selection they do. That is a new selection pressure right there.

            • by epine ( 68316 ) on Saturday December 01, 2012 @11:31AM (#42154467)

              It's only evolution if there's a reasonably clear link between your genetic makeup and your ability/probability to reproduce.

              Two errors here. First, you mean fitness, not evolution. Second, only the charismatic megafauna of our genetic endowment has a "reasonably clear" one paragraph synopsis. Try to figure out whether a small affinity change of some obscure serotonin receptor involved in bone growth regulation is deleterious or not. I dare you.

              The rest of your post seems to be spinning around the observation that the genetic fitness function is shaped by cultural memes, which are themselves co-evolving. It's almost as if natural selection has no master plan.

              Let's do a thought experiment. Imagine you have a cluster of ten genes where having eight of the A alleles makes you a genius, nine make you more than a little batshit, and the full set of ten make you A Scanner Darkly on a bad trip. On the other side, having five or fewer amounts to destination short bus. Clearly the A alleles of these genes code for smartness, and we all want that.

              But then, if two eights pair up and start a family, you end up with The Royal Tenenbaums.

              What happens within the population to the proportion of A alleles of this gene cluster? For the vast majority of people, an extra dose of the A allele would boost their intellectual powers and presumably their reproductive fitness. There would broadly be an increase. But then you lose enough to Van Gogh attrition that it cancels out the bulk upward drift.

              Likely outcome: a barber pole that spins, but goes nowhere. Yet everyone presumes there's some direction clearly labeled as "up" within the genetic pell mell.

              I listened to a podcast recently where a professor said that his students are routinely shocked to discover that simple voting systems contain cycling majorities.

              If Condorcet's paradox [wikipedia.org] disorients, what's really going on in evolution is Kowloon Walled City [wikipedia.org] (which had a population density of 1,255,000 inhabitants per square kilometer before it was torn down, roughly what you'd get if everyone in Texas moved to Manhattan, as they framed it at 99% Invisible [99percentinvisible.org]).

              We really ought to step back most of the time and view evolution as a kind of ideal gas law, as something best understood at the sweep of statistical mechanics. Yes, every atom is doing something explicable if you prefer to drill down. So was every inhabitant of Kowloon Walled City, more or less.

      • Clearly it does. It provides a selection factor which when combined with the genetic mutations mentioned in the summary (what, read an article???) gives you the ingredients for evolution.

      • by Jmc23 ( 2353706 )

        What makes you think people can't sense genetic compatability, Mr. Know-it-All.

      • by RabidReindeer ( 2625839 ) on Saturday December 01, 2012 @10:29AM (#42154233)

        I should add that selection based on culture (love, pre-arranged weddings etc) rather than fitness also does not help evolution.

        Your definition of "fitness" is not the Darwinian definition. It sounds, in fact, more like the pseudo-Darwinian conceit that "fitness" means the ability to kill or resist being killed. When Darwin said "survival", he didn't mean "last person on the island", he meant that the species in question had found a niche where its population would be stable.

        Survivability comes in many forms. Some, like tigers are primarily solitary. Some, like herd animals, depend on the group. We have ample evidence these days that in many cases, survivability (in the Darwinian sense), can come even from relatives who never directly contribute DNA to the continuation of the species.

        Love as a primarily positive evolutionary trait can be debated, although certainly being unlovable isn't going to afford many non-violent ways to swim in the gene pool. Pre-arranged weddings, on the other hand, can make the difference between a tribe being exterminated or being able to ally itself with other tribes. Systems of laws and mores can ensure that the unlovable whose sole means of propagation is rape will be taken out of circulation relatively quickly.

        Social structures as evolutionary forces are not unique to the human race. But they are a powerful contributor. If we went strictly on kill or be killed based on physical fitness, we probably wouldn't have produced a Stephen Hawking.

      • And actually there was an enormous selective pressure in this area from at least 1600 until about 1900.

        If you were unfit in an obvious way the parents would not allow their children to marry you.
        This extended all the way down to the lower classes. It even extended to your relatives.

        So even if you just had a cousin in the loony bin, you might be turned down for marriage into many families and denied the chance to procreate with that genetic stock.

        It was sort of like eugenics before their was eugenics.

        The pr

    • by binarstu ( 720435 ) on Saturday December 01, 2012 @04:56AM (#42153133)

      The parent is simply wrong. Acquisition of mutations most certainly is evolution, and evolution does not require natural selection.

      Natural selection is one mechanism of evolution, but not the only one, and evolution does not have to increase fitness. Ever since the "modern evolutionary synthesis," evolution is often defined as the change of allele frequencies in a population over time. Such change might be due to natural selection, or it might be due to other non-selective forces, such as genetic drift. To say that again, natural selection is not required for evolution. Introduction of new alleles due to mutations, random fixation or loss of alleles due to genetic drift, changes in allele frequencies due to population bottleneck events, and so on, all can cause evolution without natural selection.

      Wikipedia has more information about natural selection and non-selective factors contributing to evolutionary change [wikipedia.org].

      • The parent is simply wrong. Acquisition of mutations most certainly is evolution, and evolution does not require natural selection.

        It does not require natural selection, but it does require selection. Right now, there is no real selection. Basically any and all genes can be passed along. There's someone for everyone out there, and most of them seem to want to make babies.

        Evolution doesn't require natural selection, but it does require selection. We're not that choosy in the aggregate; almost anyone who can survive can breed, which sets us apart from many other animals, where only the "best" exampled get to breed. That means that we hav

      • by anon mouse-cow-aard ( 443646 ) on Saturday December 01, 2012 @11:53AM (#42154573) Journal
        I call B.S. on that definition. The probability of random mutations accumulating in a population to the point of creating a significant change in allele frequencies without a selective force of some kind approaches 0. Sure, random mutations occur, but they can just as easily occur in the opposite direction barring some sort of "slope" to genetic drift... If there is such a slope, then it is a selective force, though perhaps not classic natural selection. Evolution does indeed require a selective force, which traditionally has been natural selection. If you are going to say there are other selective forces, that's fine, but pure generation of mutations (genetic drift) without selection will not bring about a statistically important number of significant changes in frequency, and thus is not evolution. It is just mutational/evolutionary noise.
    • by Arancaytar ( 966377 ) <arancaytar.ilyaran@gmail.com> on Saturday December 01, 2012 @05:01AM (#42153153) Homepage


      Humans are still reproducing, surviving and dying. Traits are still selected. They're just different traits than the ones that would have been selected if humanity were still living in caves. The fitness function has been loosened, and the net is cast wider now - instead of mutations having to benefit (or not adversely affect) the immediate survival of the individual, there is more room for variety.

      A species with a secured infrastructure can afford to gamble on outliers, who would not have survived prior to modern technology. Those gambles can pay off big-time. [wikipedia.org] The absence of an outdated pre-civilization fitness function killing everyone with motor paralysis is what allows our species to benefit from a genius with motor paralysis.

      • by Mindcontrolled ( 1388007 ) on Saturday December 01, 2012 @05:23AM (#42153235)
        And this, good Sir, should end all the "idiocracy" bullshit. It won't, but it should. I wouldn't necessarily say that the fitness function has been loosened, though - only if you look at the physical aspects of it. Social aspects, sexual selection etc. are probably getting more important, the more the physical aspects are getting lost.
      • by rtb61 ( 674572 )

        Almost but not quite right. Think of evolution over time cutting from the bottom rather than adding to the top. As long as they can achieve breeding age and it is repeated in the next generation, no matter how badly equipped they are, they will continue to affect the evolutionary pool.

        With humanity there is of course something far more important, as a social species, social evolution counts far more than individual evolution. How as a species we co-operatively survive and reproduce to our mutual advantag

    • Evolution at the neutral rate is still evolution.

      On the other hand, it looks like we may have seriously lowballed our estimates of the neutral rate of evolution.
    • The simple explanation is that healt care enabled us to cheat on selection.

      What health care was there 200 generations ago?

      • Knowledge of plants that reduced fevers and fought infections, which kinds of food to ingest etc.

        Just because our ancestors didn't know *why* something worked didn't mean they didn't experiment and observe.

      • by TheLink ( 130905 )
        There was some healthcare. Wine, honey, oil, herbs, poultices, etc. But I'd say War and Agriculture was also around 200 generations ago. Agriculture allowed larger numbers of people, storage and supply of food and thus larger scale War. And War applied a fair bit of selection pressure to those numbers of people.

        Maybe one more reason why humans can run for so long is because of War. Your genes are more likely to stick around if you can run till the sun sets then hide or run so more so the victors have even m
      • by Qbertino ( 265505 ) <moiraNO@SPAMmodparlor.com> on Saturday December 01, 2012 @08:15AM (#42153751)

        What health care was there 200 generations ago?

        Pretty good healthcare in some parts of the world. Arabia and parts of the Byzantine Era, for instance, were a high culture more than a thousand years ago with complete health care coverage and other public services. Including stuff you'd have considered high-tech right up to magical in other parts of the world. Water clocks, aquaeducts, mechanical devices, sophisticated smithery and metal working, a school system, superiour math, accounting and efficiency measurement techniques, etc. As for the public healthcare, there are written acounts of people being thrown out of hospitals because they were still enjoying the pampering even though they were well again.

        Which, on a sidenote, goes to show how things go down the drain once religious fanatics take over.

    • That's what I was going to say. I've read similar stories on BigThink about how humans are "evolving" but it's hard to evolve until some form of stress is placed on humankind which enables a mutation to benefit the holder of said mutation.
      • by Jmc23 ( 2353706 )
        and you think modern jobs don't create stress?
      • by jafiwam ( 310805 )
        Ever seen Idiocracy? Out-breeding other "types" of humans will work well enough too. No stress needed, just time, and different breeding rates in whatever sub groups one chooses to define.
    • by NReitzel ( 77941 ) on Saturday December 01, 2012 @09:01AM (#42153921) Homepage

      No, it's not evolution in the way that believers in a slow random process like to picture it.

      This process is called adaptive radiation. Humans have moved into a very large feeding niche, and as a result our population and our genetic diversity has expanded hugely. Hygiene, agriculture, medical intervention, technology, and social institutions have hugely expanded the availability of places that people can survive. In an entirely natural and very old process, we have expanded our population into those places. There are more of us than there are locusts.

      The second half of the cycle is the selection part. In the previous century, wars and local famine have played a part in this not so nice aspect of the evolutionary mill. In centuries before that, famine and plague were part of the selection process. In current times, some of the selection pressures applied to isolated parts of humanity include famine, flooding, ability to avoid being a gang member, and facile birth control. Note carefully that the term "isolated" used to refer only to geographic isolation. These days, more important is political isolation. Consider the Democratic People's Republic of Korea, for instance.

      As much as some of us would like to think so, we as a species are not specially selected by supernatural powers to be immune from the evolutionary process. It goes on every day and shapes us. The cycle of adaptive radiation includes expanding into a new niche (now, the whole world), and then failure of large chunks of that population when something goes wrong. A recent instance would be the European plagues that took out 60% of the population. The descendants of that evolutionary moment are a little more resistant to Yersinia pestis, in a super-bug meets slightly better people scenario.

    • by Jmc23 ( 2353706 )
      Maybe our definition of evolution is incorrect?
  • ...that it's because in the last 200 years humans have had to live with exposure to chemicals that no life, not even our single-celled ancestors, had to evolve in the presence of... so now we don't have the tools in our genetic toolkit to deal with the effects of those substances that are completely alien to this particular Earth-bound strain of life?

    Just a thought.

    • by pjt33 ( 739471 )

      200 generations, not 200 years. The difference is a factor of 20 or so.

  • Any odds that, instead of or in addition to the rate of mutation going faster, the survival rate has also increased over the same period?

  • It's "Survival of the Fit-enough"... no longer "survival of the fittest".

    With medical technology - babies that would have died lived on. They had families of their own. Thus, passing along 'defects'/'evolutions' which would have died out as those babies would not have made it to a reproduction age.

    Doomed by our technology which was designed to save us.

    • by wvmarle ( 1070040 ) on Saturday December 01, 2012 @04:40AM (#42153091)

      All those babies surviving is something of the last five, maybe ten generations at most. And that's in the Western world. TFA is talking about 200 generations.

    • Re: (Score:2, Insightful)

      by Anonymous Coward

      Actually, this is how evolution works, so "Survival of the Fittest" is still applicable. If the current environment allows those individuals to reproduce and pass on those traits, they are the most fit. We will be a bunch of fat-ass couch potatoes eating chips watching CSI-dancing with the honey boo boo. Just as if the weather turns bad and only gingers can survive, then they are the most fit. Evolution does not care how the fittest are created, whether by man made environments or by natural influences.

      • Re: (Score:2, Insightful)

        by Johann Lau ( 1040920 )

        We will be a bunch of fat-ass couch potatoes eating chips watching CSI-dancing with the honey boo boo.

        We are (d?)evolving into roughly two classes: the manipulated and the manipulators. Which isn't to say that everybody isn't a bit of both, but still: you are missing the "elite(s)" in that picture. I would argue they get dumber in their own ways, too, but they sure as fuck aren't sitting at home staring blankly at the TV. So that's a bit simplicistic, yeah?

        Perhaps you do not so much believe in evolution as

    • by flonker ( 526111 ) on Saturday December 01, 2012 @04:59AM (#42153149)

      The frightening aspect of this is that population may expand its genetic diversity to fill the 'fit enough" gene pool. Then it will overflow the "fit enough" gene pool by creating mutations that can't survive even with health care, bringing survival back down, albeit with increased genetic variety such that many can't survive without constant medical treatment.

      That is to say, we will evolve to require medical treatment.

      • by Chrontius ( 654879 ) on Saturday December 01, 2012 @05:36AM (#42153283)
        That's okay. In about a generation, everyone will be cyborgs anyway [wired.com]. Seriously, Intel plans on shipping 14 nanometer chips in 2013; 5 nanometer processes are under development already, and at that point we can start seriously thinking about using the 5nm process to make machines to make utility fog [wikipedia.org].

        Your natural body is just a device for building a brain and a pair of gonads, at that point, and selective pressures only work on it in this scenario are those that render cyborg-you sterile, destroy your brain before it can be transplanted into a cyberbody, or make you better able to talk a partner into raising a family with you.
      • by Hentes ( 2461350 )

        Not necessarily. You can keep people alive while at the same time ban them from breeding.

      • by Jmc23 ( 2353706 )
        umm, what makes you think most westerners aren't there already?
    • by imidan ( 559239 ) on Saturday December 01, 2012 @05:28AM (#42153251)

      Nonsense. Survival of the fittest is still occurring, it's just that the fitness criteria have changed. As you say, "babies that would have died lived on" -- but mostly that happens for those parents who have either the money or the health insurance (and the medical facilities) to deal with what would previously have been an "unfit" baby. Natural selection continues through societal means: the costs of birthing and raising viable children are inversely proportional to the health of the baby; children with difficulties are more expensive to raise.

      There is still selection pressure, but in developed countries it's coming more from societal sources than from environmental sources. And the societal pressure isn't so worried about things like good eyesight or height, or those sort of physiological characteristics; it's about access to health care (whether that comes from parents with money or states with social safety nets).

      And I would argue that even though humans are in charge of the programs and policies that affect these new fitness criteria, they are still fitness criteria because they are being applied to populations, rather than to individuals (except in very special and statistically insignificant cases). So, survival of the fittest is still alive and well, and being implemented inadvertently by human policy.

  • Times of plenty (Score:5, Insightful)

    by chrisjbuck ( 950790 ) on Saturday December 01, 2012 @05:14AM (#42153203)
    I think population dynamics show that in times of plenty (little natural selection, abundant food) populations explode, what the human population has been doing the last 100+ years. It's the spring that doesn't come or massive outbreak of disease or new dominant predator that culls the population, when that selection occurs the random genetic variations may give rise to competitive advantages. It is only after the population goes through the selection event that any mutations that proved advantageous will spread right through the population, then the population has evolved. Before the selection event the population is just randomly diverging.
    • Technically the "randomly diverging" is also evolution, but the parent is for the most part spot-on and I'm too tired to write this sort of thing at 4:44 AM. Instead, please enjoy the benefits of my karma; had I mod points, you'd have gotten an "insightful" from me.

      Actually, I am a biologist.

      Mods, please do me a favor and add some "insightful"?
  • True! (Score:5, Insightful)

    by rew ( 6140 ) <r.e.wolff@BitWizard.nl> on Saturday December 01, 2012 @05:19AM (#42153221) Homepage

    Absolutely true!

    Evolution works that way: In good times, a big population is generated that has great genetic variety. When bad times come along, the bad genetic variations will be removed from the population.

    Suppose for instance that suddenly tomorrow all oaktrees had pollen that is deadly to most humans. The genetic variations builtup over the last 200 years might have provided a (possibly small) percentage of the population that is resistant to the deadly pollen. The result would be that a small group survives and starts working on a new gene-pool.

    Yes, genetically we have been living in "good times" the last generations. More and more "slight defects" in the genetic pool are able to survive into mature ages.

    A friend is totally colorblind. A genetic disadvantage, you'd say? Nope, his "grayvision" is a LOT better than that of most of us. Apparently he can spot camouflaged army-material from way further away than us normal people. When suddenly THAT becomes a winning trait (i.e. those that don't have it die), his descendants will form a larger part of the population.

    This expansion of the gene pool also allows for combinations. Suppose the guy with the super-vision marries the gal with the super hearing?

    • Re: (Score:2, Troll)

      by Curupira ( 1899458 )

      Absolutely true!

      Suppose for instance that suddenly tomorrow all oaktrees had pollen that is deadly to most humans.

      Hi, Mr. Shyamalan! I didn't know you had an Slashdot account!

    • Re:True! (Score:4, Funny)

      by mrmeval ( 662166 ) <mrmeval@@@gmail...com> on Saturday December 01, 2012 @09:49AM (#42154103) Journal

      As to the color blindness a young kid who I knew to be smart wanted a job in electronics. I like to rant and was giving him a ride somewhere and I lost it. I did a 35 minute rant on why anyone why would prevent a color blind person from working in electronics needed to be beaten to death. That only a moron would use only the color codes of resistors, capacitors or wires with ...ahem blind faith some other moron didn't load the wrong paint in machine or the wrong value or even the wrong damn part. Add in a lot of expletives. I also mentioned I'd fire anyone who repeatedly trusted something as unreliable as color, that's what test equipment is for.

      This was just me doing a rant, I do express myself with some drama and vitriol but I never thought it would have the impact it has. The kid broke with the family business, got a degree and is making more than I am. He can spot miswiring easier than people with ordinary color vision. I'm now going to test if he can spot Army ACU's on a paisley couch among other things. ;)

  • by climb_no_fear ( 572210 ) on Saturday December 01, 2012 @05:39AM (#42153293)
    depend on your environment sometimes. For example, heterozygous mutations in the gene that lead to cystic fibrosis probably increase resistance to cholera (by lowering electrolyte loss in the gut). Eliminate cholera in the modern world and the advantage apparently disappears. Similar for sickle cell anemia and malaria (depending of course, where you live or travel, this may still be highly relevant for you). And "fit enough" has always been good enough throughout evolution.

    This is probably why primates need vitamin C, since we all lived in an environment with plenty of it and there was no selection against loss of the gene which occurred in one of our ancestors.

    It is sometimes difficult to see the advantage of a particular mutation (resistance to dioxins because cytochromes don't metabolize them) or other mutations which are only beneficial in combination with others. Mutations in FoxP2 http://en.wikipedia.org/wiki/FOXP2 [wikipedia.org] plus others probably led to human speech. There are rare individuals with mutations in a gene which regulates LDL (the "bad" cholesterol) http://en.wikipedia.org/wiki/Familial_hypercholesterolemia#PCSK9 [wikipedia.org] that have very low LDL levels and are apparently perfectly healthy. They lack a gene most of us have and can eat a "modern" diet with a dramatically reduced cardiovascular risk. This is one of the ways in which speciation occurs.
  • 200 generations....well, that's not a very specific amount of time, so I can't really comment on that specifically, but I wonder if it the whole "more rare genetic variations" has something to do with having bigger and more diverse populations inter-mixing. If there's a general trend in the last couple hundred to couple thousand years, it's that you've got people clumping together in bigger groups, developing complex trade and migration, all of it adding up to a much broader gene pool than the days of the h

  • by Baldrson ( 78598 ) * on Saturday December 01, 2012 @06:10AM (#42153389) Homepage Journal
    It is the theocratic dogma that heterogeneity (localized diversity) yields symbiosis, as in "diversity is our strength". To even question whether this might be wrong is tantamount to being a pariah in all aspects of life from personal to professional -- so powerful is the state-sponsored religion incorporating this dogma.

    As usual, theocratic dogmas, rigorously enforced, frequently have unintended consequences. In the case of the dogma of heterogeneity there is the unintended consequence which evolutionary dynamics calls "horizontal transmission". Horizontal transmission is a mode of evolutionary success is based on, what in the vernacular we might call, "hit and run": The evolutionary fate of a stationary system (organism or ecosystem) is decoupled that of another, temporarily co-located, but mobile, replicator.

    The result is always the same: The mobile replicator's evolutionary optimum is to totally disregard the viability of its temporary "partner" since it does not share in the fate of the "partner". This relationship is sometimes called "parasitism". That, in an age of jumbo-jet air transport, we might see such evolutionary dynamics play out is as inevitable as it is "sinful" to even think about.

    The religious dogma demands that heterogeneity be thought of as evolving only "symbiosis", not "parasitism". This would be the case if there were no escape route for the immigrant replicators -- as they would be forced into "vertical transmission" which, in the vernacular means "sleeping in the bed you made for yourself (and others)". Even if we were somehow able to shut off further migration after allowing immigration, the costs of evolving symbiosis are profound: The vast majority of the immobile heterogenous ecologies resulting from the initial period of immigration would include at least a few replicators that might be thought of as "defectors" in an evolutionary prisoner's dilemma. Therefore the vast majority of ecologies would experience at least pathology if not death outright.

  • If this discussion is any indicator, it's devolution that's accelerating.
  • 200 generations, at 30 years per generation is 6000 years.

    Or is the age between generations less than that?

  • by SpinyNorman ( 33776 ) on Saturday December 01, 2012 @08:46AM (#42153859)

    In a massive study on genetic variation among humans, researchers found that most changes have occurred in the last 200 generations, too fast for natural selection to catch up.

    This statement appears to reflect a misunderstanding of how evolution plays out in practice.

    The way evolution is often taught is that the small genetic changes in each generation make a difference to the evolutionary fitness (relative to his/her peers) of the individual right away, but that the changes are so small that it takes very many generations to see divergence of sub-populations of the species and hence noticeable evolutionary change.

    The reality of evolution - "puntuated equilibrium" - is different from this simplistic teaching model. What really happens is that genetic changes accumulate over very many generations but don't have much if any immediate effect on evolutionary fitness since in practice these small, incremental, personal changes are often not what drives evolution. What really drives evolution (per the inference of the fossil record) is when the *environment* (weather, food supply, disease, competitors, etc, etc) changes, often very quickly, causing accumulated genetic change to suddenly become relevant... what had previously been a benign genetic change (disease resistance or susceptibility, etc, etc) no suddenly becomes a huge change in evolutionary fitness in the new environment, and and the fate of different genetic subpopulations becomes very differnt (we see visible divergence).

    This is "punctuated equlibrium" - long spans of no visible evolutionary change (equilibrium) are puntuated by brief spans of rapid visible change as accumulated genetic drift suddenly becomes relevant due to environmental change.

    So... the notion of 200 generations being too quick for "natural selection to keep up" is bogus. Natural selection mosltly doesn't happen every generation - it only happens when those infrequent major environmental changes occur.

    • by EmagGeek ( 574360 ) <gterich&aol,com> on Saturday December 01, 2012 @08:52AM (#42153893) Journal

      I think what the submitter was getting as was that we are carrying a higher load of negative traits because natural selection is failing to eliminate them.

      For example, one reason cancer is becoming more and more prevalent is because people who would normally die from it before they can reproduce, are instead being kept alive through technology to reproduce and transmit their higher susceptibility to cancer to the next generation.

      (please not that I said "one reason," not "the only reason," because I know some environmental hot head is going to flame me for saying this)

    • by Jmc23 ( 2353706 )
      The mind forms the pattern, the words flowing from his lips create the prison, bars of words restrict him. He smiles at the beauty of his own reflection.

"No, no, I don't mind being called the smartest man in the world. I just wish it wasn't this one." -- Adrian Veidt/Ozymandias, WATCHMEN