Sunday, January 07, 2007

Have Humans Stopped Evolving?

Yesterday's Quirks & Quarks radio show had a segment on human evolution. Here's the description from their website:
January 6, 2007: Are Humans Still Evolving?

Evolution has made us what we are today, and we're increasingly learning what made modern humans different from our ancestors. But many scientists think that we have now removed nature's control over our genetic legacy. Our technology allows us to control our environment and survival to the degree that we may have stopped human evolution altogether. Is our growth and development as a species at a standstill? If not, what will we become in the future? Find out this week on Quirks & Quarks.
Listen to the podcast. The segment on human evolution starts about one third of the way through the show.

The idea that humans have stopped evolving is ridiculous. It reflects a deep and fundamental misunderstanding of evolutionary theory.

Fortunately, the blurb on the website doesn't reflect what was broadcast. The host, Bob McDonald actually does a very good job of sorting through the rhetoric and the show is an excellent summary of current scientific thinking. It's by far the best thing about the rate of human evolution that I've ever heard on public radio.

One of the people interviewed on the show is Steve Jones from University College, London. Jones claims that almost everyone is reproducing these days so natural selection isn't affecting humans any more. He contrasts the situation today with that in Shakespeare's time when 2 out of 3 babies didn't survive to adulthood.

This is one of the weaker parts of the show. The claim that natural selection isn't working on humans is false. It is refuted by Jones himself later on in the broadcast, and by Noell Boaz from Ross University in Dominica.

Let's deal with the increase in longevity that we've seen in some societies over the past 500 years. We'll dismiss the obvious bias in equating what happens in Caucasian societies with evolution of the entire species. What about the fact that people in London live longer today that they did in 1600? Does this have anything to do with evolution?

Jones thinks so. He says,
Now a lot of those deaths in the old days were due to genetic differences but if everybody stays alive, everybody gets through, no more natural selection.
I don't think so. It isn't obvious to me that people were surviving in 1600 because they had better genes. People died for all kinds of reasons that had nothing to do with genes. A famous example from the nineteenth century was the London cholera outbreak. In that case, you died if you were close to the contaminated Broad Street Pump and not because you had bad genes.

If you died of infection or malnutrition in 1600 it was probably due to bad luck and not bad genes. As living conditions improved, everyone benefited equally, not just those who might have been genetically susceptible. Thus, natural selection wasn't all that important back then and most of the improvements in health in developed countries have affected evolution directly. (The quibblers are waiting to pounce, so let me address two objections to that statement. First, there are other, more modern, medical advances that do affect selection—wait for them. Second, there are some examples of genetic effects on whether you survive disease. Some people might have been more resistant to the Black Plague, for example. Such examples are exceptions to the rule. The common assumption that most deaths in the past had something to do with natural selection is what I'm addressing here.)

So, let's be skeptical about the specific argument that Jones is making, namely that increased longevity, per se, is proof that the effect of natural selection is diminished in modern societies. A lot of negative selection—selection against less fit individuals—is still taking place in utero just as it always has. Lethal mutations result in spontaneous abortion or failure to produce viable sperm and eggs. This form of natural selection hasn't changed significantly. Also, even though severely handicapped children born today may survive longer, they probably won't reproduce.

On the other hand, there are medical advances that do affect natural selection. The most obvious one is the invention of eyeglasses. As Jones points out in the show, people with a genetic disposition for bad eyesight can now survive whereas back in the hunter-gatherer days it might have been much more difficult. Thus, natural selection in favor of good eyesight has been relaxed because of eyeglasses.

What does that mean for human evolution? To its credit, the Quirks & Quarks show doesn't jump to the false conclusion so common among the general public. Evolution hasn't stopped, it has increased! The removal of negative selection causes previously detrimental alleles to survive in the population; therefore, their frequency increases. Thus, evolution is happening today but was blocked by negative selection in the past.

The same argument applies to all medical advances that allow for previously handicapped individuals to survive in modern society. Human evolution is being accelerated. This is a point worth emphasizing because the opposite conclusion is so common. Most people think that removing strong negative selection means that evolution has stopped when, in fact, the exact opposite is true! The misconception arises because the general public thinks of evolution as a progressive improvement in the gene pool. Modern medicine is allowing "defective" individuals to survive. This can't be evolution according to that false understanding of evolution. (There are other things wrong with that false argument; namely, the concept that people with myopia or diabetes are somehow lesser citizens. This isn't the place to get into that discussion.)

Strong negative selection acts as a brake on evolution. It slows evolution down. Remove the brake, and evolution speeds up.

There's more to evolution than natural selection. Bob McDonald interviews Katherine Pollard from the University of California, Davis. She points out that much of evolution is due to random genetic drift. Drift has nothing to do with natural selection, so whether or not selection has decreased will play only a minor role in whether humans are evolving. You can't stop drift and you can't stop mutations. You can't stop human evolution. As McDonald puts it, "we still will evolve ... it's not the kind of evolution we imagine."

Evolution is not just the result of survival of the fittest. Furthermore, it is not progressive in spite of the fact that this misconception is widespread. As McDonald says in closing, "... this is an illusion about the way that evolution works. Evolution has never guaranteed improvement or progress, just change."

Change is good. It's good that humans are evolving. Things can only get better, right?

25 comments:

  1. On the other hand, there are medical advances that do affect natural selection. The most obvious one is the invention of eyeglasses. As Jones points out in the show, people with a genetic disposition for bad eyesight can now survive whereas back in the hunter-gatherer days it might have been much more difficult. Thus, natural selection in favor of good eyesight has been relaxed because of eyeglasses.

    Not quite; we may be able to deal with foggy vision a bit better than before, although I'm not quite sure about that.

    But we do need much better eye-muscle coordination than before. It's not about throwing a spear at a moving target every day or so; it's about maneuvering a one-ton bullet through 6 lanes of traffic for hours, while seriously sleep-deprived. And that affects survival as directly as hunting did.

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  2. You're incorrigible, Larry. The very idea that selection is still applying to humans... ;-)

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  3. Larry Moran: "The idea that humans have stopped evolving is ridiculous. It reflects a deep and fundamental misunderstanding of evolutionary theory."

    This is one area I am always having to address on the blogs. Evolution happens every time someone selects a mate.

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  4. This aspect of evolution can and has been tested by taking humans in one of their most sexually active stages and artificially crowding them into an enclosed structure. I think it's called a "High School".

    In this exaggerated environment, even the slightest misstep can result in the loss of a potential mate, a poorly chosen word, provoking a bullying response from a competitor, even a minor facial blemish. In this hyper-charged environment, social graces and conformity to cultural norms can often ensure successful mating.

    Of course, some members of the species look to other than the superficial aspects of a potential mate and look for more intangible qualities, such as loyalty, sensitivity, intelligence. But this is also evolution, of course.

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  5. Larry

    There hasn't been a new genus in 2 million years and a new true species in historical times. All that can be documented is extinction without a single replacement or any new species to occupy any novel new niches. Intraspecific varieties and subspecies are all that the Darwinian model has ever been able to generate. None of these are incipient species. Creative evolution is finished and has been for a very long time. All we see today is rampant extinction. Pierre Grasse realized it as did Otto Schindewolf, Robert Broom and John A. Davison.

    Sorry about that.

    Now please don't delete this comment as so many blogczars, like Spravid Dinger and Esley Welsberry are prone to do. I don't want to have to start calling you Marry Loran don't you know.

    "A past evolution is undeniable, a present evolution undemonstrable."
    John A. Davison

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  6. I recommend you visit American Chronicle for January 10 where Kazmer Ujvarosy introduced my essay "The Darwinian Delusion" as an antidote to Dawkins' "The God Delusion."

    http://www.americanchronicle.com/articles/viewArticle.asp?articleID=18813

    "A past evolution is undeniable, a present evolution undemonstrable."
    John A. Davison

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  7. So THAT'S where Noel Boaz is these days .... I had no idea.

    Great post.

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  8. But we do need much better eye-muscle coordination than before. It's not about throwing a spear at a moving target every day or so; it's about maneuvering a one-ton bullet through 6 lanes of traffic for hours, while seriously sleep-deprived. And that affects survival as directly as hunting did.

    I'm not sure if I agree that it is a matter of eye coordination. Maybe, maybe not. But I do like the idea of thinking of selection in relation to driving.

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  9. As a matter of fact Homo sapiens is apparently the youngest mammal species to appear on earth and in my view the last mammal to ever appear. We are no more than 100,000 years old. I am also confident that Naanderthal was our immediate ancestor simply because there was no other candidate available when we first appeared. It is also possible that Homo sapiens was produced on more than one occasion. Apparently we represent the terminus of a "prescribed" evolution. All that remains is extinction which is all that can presently be verified.

    "A past evolution is undeniable, a present evolution undemonstrable."
    John A. Davison

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  10. As a matter of fact Homo sapiens is apparently the youngest mammal species to appear on earth and in my view the last mammal to ever appear

    John:

    The earliest modern human fossils predate the earliest Neanderthal fossils by a few thousand years and are found many thousands of miles away. If we extend the record for both groups in a reasonable way using the stone tool record (which leaves more evidence) then this reamins true but the modern humans or their immediate ancestors are hundreds of thousands of years earlier than the earliest neanderthals.

    And humans came on the scene only once.

    If dogs are a different species than wolves, they are an example of a more recently evolved species.

    Your assertion that humans are the most (let's say "one of the most" recent species is probably not very far from the truth, though, because during the latter part of the Pleistocene, most of the action in Mammal World has been extinction not speciation but it is during this time that humans arose.

    Regarding Prescribed Evolution ... I think it is only fair that Professor Moran field that one ... this is his blog site after all....


    I appreciate your interest in human evolution!

    GTL

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  11. All dogs are wolves or if you prefer all wolves are dogs. The hybrids beteen dogs, coyotes and wolves are all fertile.

    As for humans, I am defining humans as modern man (Homo sapiens.) You are definitely wrong of you think that Homo sapiens is older thamn Neanderthal. I repeat that Homo sapiens is the youngest mammal ever to appear on earth and he has not evolved a micron since his initial appearance. If anything he has accumulated a number of deleterious genes that will, if it continues, lead to his early extinction, if he doesn't commit suicide first by destroying his environment. That, he seems bound and determined to achieve.

    "A past evolution is undeniable, a present evolution undemonstrable."
    John A. Davison

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  12. Just because wolves and dogs can make fertile wolfdogs doesn't mean they are the same species. You wrongly believe that total reproductive isolation is required for two species to be, well, species. You may have a point that the definition of species isn't very clear cut and hotly debated in biology, but wolves and dogs are different species. By way of analogy (and ripping off of Dawkins) human beings are the product of an unbroken line of ancestors all the way back to, arbitrarily, an ancestral eukaryote cell. That is, I could mate and yield fertile offspring with my immediate ancestor (were they still living); that ancestor could do the same with its immediate ancestor, etc. until our eukaryote cell. Yet, at the end of the day, I am not of the same species as the ancestral eukaryote cell. Another example would be ring species

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  13. ...with a link to Wikipedia about ring species! http://en.wikipedia.org/wiki/Ring_species

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  14. Wikipedia is nothing but a willing dupe for Darwinian mysticism. Darwinism in all its disguises never had anything whatsoever to do with creative evolution, absolutely nothing. Got that? Write that down.

    "A past evolution is undeniable, a present evolution undemonstrable."
    John A. Davison

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  15. I don't get it.

    What I do understand is that most people here don't either, so I suggest you peddle your radical views elsewhere than us dupes. Maybe even that's a lost cause.

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  16. Dunbar, whoever that is.

    You got that right.

    I love it so!

    "A past evolution is undeniable, a present evolution undemonstrable."
    John A. Davison

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  17. you make your argument based on a technicality. I know the definition of evolution for scientists means change can happen in both directions. This is where I think the genaral public's misconception should be given more credence because it not a bad thing for them to think evolution is progressive. The word is EVOLUTION , not REVOLUTION, so the 'official' meaning of the term should IMO be changed to reflect this.Or at least have an addendum term everyone can remember that means precisely forward evolution. Afterall, what amount evolution would take place if progress didn't happen sequentially? None. We'd still be bacteria if we took two steps back for every one forward. Thats not to say these organisms are any less important, they provide the base we stand on. People with disabilities are not lesser beings, but they do have less
    fit bodies, and despite what you say, thats still important. Genetic drift is important mainly for small populations, but there are 7 billion of us , more biomass than any other land animal outside of insects.We're now constantly mingling and fixation of alleles is becoming less likely( at least in the short term).People base some of their assumption thaty evolution has stopped based on what is going to happen in the near future, where deleterious/recessive alleles are no longer selected against. but reach a kind of nominal distribution. Blond people are not going to become extinct just a lot less of them.
    As you stated natural selection is becoming less important as people have changed the environment making it much easier for people with minor disabilities to get along. Culture has evolved to a level were we think that the mental is at least as important as the physical. If they have them, people with mental conditons can often be treated more effectively than physical conditions. Or they can hide these traits to pass on thier genes.
    Another biggy I'll just open on is that of unnatural selection.We're coming up to a time when genes can be screened or altered and so everyone's genetic profile can be made almost uniform.Evolution will have really stopped then. People have awareness about this.I remember a 60's Twilight Zone ep that dealt with this very concept. More importantly WWII was all about that.
    The Scientists have too big an ego and dont want to change for even something thats logical when that is supossed to be the mantra.

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  18. lesaracen, did you hear a loud "whooosh!" noise after you read my posting?

    That was the sound of a point going over your head.

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  19. I would argue that natural selection has stopped in modern humans because anyone can reproduce. The vast majority of people can and do reproduce and fitness has absolutely zero to do with it. In fact qualities that many would consider to represent "fitness" like intelligence or the ability to gather resources and status have nothing to do with reproductive fitness. As an example, your local biology professor who makes an income far above average may have 2 or 3 kids, while a welfare mom in the slums might have 7. But the point is, no matter how tall you are, how fat you are, how poor or rich you are, there is a human somewhere, sometime who will reproduce with you. So there doesn't seem to be much selection going on.

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  20. Sorry, but being able to manipulate the environment drastically changes the rate at which we evolve. It's mathematics....the more drastic or the more variance in the environment, the faster you evolve. We've brought evolution down o a screeching halt...this is simple mathematics, if you believe in evolution, then you cannot dispute this without sounding superstitious.

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  21. I agree that we may be evolving, but I do not agree that it's in an upward direction. My reasoning behind this is that we have almost overcome all natural predators. We have evolved enough to learn and create ideas, and that knowledge will always grow, allowing us to do things like create better medicine that allows us to live longer than previous generations. This is not the human race evolving; it's only medicine that prolongs our lives. At this point, the only way to evolve upward would be selective breeding or the emergence of a new predator on Earth.

    Midd

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  22. My feeling is, and I state it as such, not as assertion of fact, that no matter what control we think we exert over such things as environment or evolution we remain at the mercy of the universe. All our concepts of human superception are selfindulgent fantasy.Sure, we can do more than our distant ancestors, but less as well. For every advance, something is left behind. The mistake is in assuming early man to be a helpless victim of his environment. Feared as a savage and furious predator, even the mighty mammoth fell to these relentless packs of vicious pointed stick wielding beasts.
    My point is that we are and likely will always remain part of, and as such subject to, nature. All our illusions are just that. Illusion. We're not alone in using tools to master tasks, nor does our expertise absolve us from nature. Quite simply, the higher you climb the further you can fall.
    Planet of the Apes anyone? :)

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  23. We are great apes, the third chimpanzee- Homidae!

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  24. As of right now I think that evolution has slowed to a significant crawl. At this rate I mean that people will still look like people even 50 million years from now (Not counting everyone becoming brown skinned, men becoming more effeminate or women being the same size as men, or everyone getting bigger. All these will continually progress or regress depending on cultural evolution as the primary force).
    Even genetic drift doesn't really matter. It works neatly in a lab (I did the probability experiment for my minor in genetics) but it doesn't work nearly as well in actuality. It's not nearly as strong a force evolutionists make it out to be. This is because of genetic fail safes that are responsible for much of the very spontaneous abortions you mention. Some combinations of genes just don't work. That's how one prediction put forward by drift theory, death spirals in a small enough population, occurs. Another thing is that we now have a permanent social memory, so we'll be immediately cognizant of any major changes and put a stop to them.

    But human evolution will happen nonetheless , quite soon. But it will be due a new force; artificial selection

    Another point is that I wish evolutionists would make up their mind about what evolution is. I learned in uni that evolution is the tendency towards greater complexity, speciation and nichification. But then I also learned it encompasses any change, at all, in gene representation. These two definitions are NOT mutually inclusive. Maintenance of a present state or regression from a present state that doesn't lead to forward evolution (new species) and may in fact likely lead to or cause extinction should be termed steady state equilibrium and devolution.

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