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LostInParadise's avatar

Are you ready for an evoltionary controversy?

Asked by LostInParadise (28465points) March 1st, 2009

No, not whether or not evolution is true. Go somewhere else for that. I am talking about a recently published book, http://www.amazon.com/000-Year-Explosion-Civilization-Accelerated/dp/0465002218/ref=sr_1_1?ie=UTF8&s=books&qid=1235927706&sr=1-1 , that states that, against the conventional wisdom, evolution of man has not stopped in the last 10,000 years but has actually sped up.

For one thing, there are a lot more of us now than there were then, so there is an increased chance of a favorable mutation. They claim that the switch to agriculture was such a major change that it applied increased evolutionary pressure to adapt.

One curious claim that the authors make is that part of the evolutionary explosion was due to having sex with Neanderthals (there is an ugly image for you) and that only a tiny amount of it would have been sufficient to have favorable Neanderthal genes join ours.

Perhaps the most contentious claim is that European Jews evolved just recently to be more intelligent. I can’t summarize the whole argument but I can give an abridged version. There was certainly pressure for the European Jews to evolve. They were barred from land ownership, but were given free reign for a while in more cerebral areas of banking, insurance and other financial areas due to the Biblical injunction against usury. There are unique Jewish genetic diseases that may be of the type where a single copy of a gene gives an advantage but two copies cause a disease, similar to sickle cell anemia. Finally, European Jews score about 12 points higher on IQ tests, which may not seem like much, but can make a large difference once you get two or three standard deviations from the mean and may explain why European Jews account for 25% of Nobel laureates.

In perusing the book in the bookstore I found some of the scientific explanations a bit hard to follow. I will wait till the book hits the local library.

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33 Answers

mangeons's avatar

No, I’m not ready. Seriously. STOP IT.

marinelife's avatar

I certainly would not accept the latter part of that argument from the data you presented. IQ tests are notoriously skewed with cultural biases.

nikipedia's avatar

I mean, the cool thing about science is that my opinion is irrelevant. I might hate all the conclusions from the book but if the data support them, I’d have to accept them. (Of course, this invites a debate about how good the scientific method really is and how much data you need to form a substantive argument…)

Based on my understanding of population genetics, I do not think 10,000 years is a sufficient period of time for any gene or set of genes to reach an appreciable concentration. And something like intelligence is clearly a multigene phenomenon. So I’m skeptical of that claim. And the other ones. Maybe we should both read the book and meet back here in a couple weeks?

Harp's avatar

Even if that had been the case, it seems like more recent developments would change that dynamic. We’ve only had truly effective medical technologies for a few generations now, and those are on the verge of dramatically increasing in effectiveness. What will be the long-term evolutionary impact of these? They may radically mitigate the disadvantages of unfavorable genetic mutations, allowing them to persist in ways they wouldn’t have centuries ago.

If technologies relieve selective pressures, then would genetically transmitted technical aptitude be the new evolutionary currency, replacing strength and disease immunity? It seems like globalization, also a relatively recent development, would keep this from becoming a strong selective factor. To confer a selective advantage, technical prowess would need to increase the chances of the individual’s genes being transmitted. Leaving aside the painfully evident truth that the nerds aren’t the ones getting the hot dates, globalization works to make technical advances spread rapidly, so the survival benefits accrue even to individuals who don’t have that prowess.

Jack79's avatar

Yes, I believe in this theory too. I have not read the book, so I don’t know if I’d agree with it 100%, but evolution is a dynamic process that does not wait for mutation and happens slowly over every generation. Even though I am not a scientist, it seems quite reasonable that it would have sped up over the last 10,000 years, just as the Jewish example seems to me more than probable. I’d also expect modern humans to have a better brain and sight but less strength than the average 100 years ago, and maybe just two generations from now our grandchildren will have much faster fingers with the ability to break the high score on Playstation 13, but won’t be able to tell a lettuce from a poisonous mushroom, nor will they need to.

Due to genetic engineering (ie throwing their children off a cliff), the ancient Spartans were taller and stronger than the Athenians, and made ferocious fighters. Yet not ONE of the philosophers we know of today came from Sparta. You can see the results of that policy even today, and there are similar differences like that everywhere in the world. It’s not that people evolve into a different species overnight, but there are certainly differences between “African-Americans” and Africans, “Irish-Americans” and Irish and so on, just like there are all sorts of differences between Argentineans and Spaniards, Brazilians and Portuguese and so on. On all sorts of levels.

laureth's avatar

While there are billions of people here, making for a greater chance of random mutation popping up, there are also billions of people here to water that mutation down and drown it in sheer genetic noise.

To best preserve a trait, plant and animal breeders keep a population small and relatively inbred. A similar thing happened to European Jews because of the social stigma of Jewishness and the tendency of Jews to marry other Jews, so they get to keep the best of their traits (like greater intelligence) but also the worst (like Tay Sachs). Even though intelligence is clearly a multi-gene trait (and also related to “nurture”), those circumstances are right to pass it on.

However, if a breeding population doesn’t keep to itself, I don’t understand how such traits wouldn’t effectively disappear in short order (appearing only if two carriers somehow make offspring). I’m not saying it’s impossible, but it seems improbable and I’d want to know more.

As far as there being “enough time” to evolve since then, I think there has been. We see trait adaptation in other animals with shorter lifespans than us, within a few years sometimes. A prominent example is the peppered moth in England, who adapted to increased soot pollution by becoming darker colored themselves. (Presumably the lighter ones were easier to see and eat, allowing darker ones to live longer and breed more.) Surely the Spartan example ^up there^ is a similar kind of pressure. It just needs to happen in a small enough population bottleneck.

marinelife's avatar

@Jack79 All the philosophical Spartans just left town.

Jayne's avatar

@Jack79, we would only develop better eyesight and faster fingers if the ability to prosper in the workplace and play video games enhanced our ability to reproduce. The latter, clearly, does not, and I believe that people on the lower rungs of the economic ladder actually tend to reproduce more slowly than the wealthy. So perhaps within a select upper-class set eyesight will be selected for (if indeed it does carry an advantage in employability beyond statistical error, which I rather doubt), but not in the general population any more than it always has been. A trait needs to have a real effect on whether or not a person reproduces, whether by benefiting their survival or allowing them to attract a mate, in order to evolve over time (and with a growing, more mobile world population, it is probably even more difficult for a trait to establish itself, because unlike in a closed group where an insignificant trait can pop up by chance, in today’s world it would usually be quickly diluted and never get a chance to reinforce itself). As several people have already mentioned, there is very little pressure based on ability to survive because of modern technology- I would further argue that with the increasing connectedness of the modern world, there is or will probably be a decrease in social selection as well, as it becomes easier for anybody to find a mate. (Yes, online dating sites are going to hinder human evolution. I guess it might take a while).

LostInParadise's avatar

@laureth, Genes that provide an advantage do not get drowned out. Once a gene establishes itself in a small portion of a population it will continue to spread.

One thing the book has done is to make me curious about genetics. If anyone knows of an elementary text that goes into the math of gene propagation, I would be most appreciative.

Jayne's avatar

Ah, but I believe it does. Let me explain. A new mutation is almost certain to be recessive, which in order to expressed, and thus to carry any advantage, must be conferred by both parents. This is not likely, in turn, unless both parents have that gene on both chromosomes, and this unfavorable probability worsens exponentially if the trait, as almost all are, is governed by multiple genes. So even if the first small community with a trait are able to reproduce because of it, they will not necessarily pass the trait on; thus, evolution will be slow and unreliable at best. Therefore, a trait must be inbred within a community to create a solid enough genetic foundation to guarantee that it will be passed on and, accordingly, that natural selection and evolution will favor it; essentially, almost everybody in the community must carry all of the necessary genes on one or both of their chromosomes. If the community is ‘diluted’ with outsiders who do not carry the gene, then this foundation will not build up. This lack of consistency in passing along genes also allows those outsiders to inject their own, contradictory genes instead (whether of the old variation or another mutation). A person can only carry a limited number of genes governing a certain trait, and you can imaging that if the ‘outsiders’, having built up the aforementioned foundation, always provide their gene to the offspring, while the ‘community’ only does so sometimes, the outside gene will dominate, thus preventing expression of, or even wiping out, the mutated ‘community’ gene.

laureth's avatar

Yeah. What @Jayne said!

LostInParadise's avatar

My reasoning is that if a gene, even a recessive gene, is in say 1% of a population then assuming that no competing gene provided better fitness then it would continue to be in 1% of the population and if the gene provides better fitness then it will slowly increase its presence.

Jayne's avatar

That is the simple view of evolution. But even without taking into account the complexities I mentioned above, it is clear that there is a contradiction in that idea. A person cannot have competing genes- or if they do, there is a problem. So the fact that evolution occurs at all proves that genes are removed as often as they are added, which means that you cannot rely on that 1% never being decreased. Now, evolution favors useful genes if we look at the big picture, but the whims of fate and the details of heritability (see my post above) mean that on a small scale, where your 1 percent is concerned, it is as likely as not, depending on the dynamics of the population, that the number of people possessing the gene will decrease as opposed to increasing.

nikipedia's avatar

@Jayne: Why do you say a mutation is more likely to be recessive?

Jayne's avatar

@nikipedia; because that’s what they taught me in 9th grade biology. Actually, I barely remember bio; I was simply building off of the idea that a new trait will in many cases require other genes to provide supporting features, and if a gene were to mutate straight to a dominant form it would lack that surrounding architecture and therefore fail. Instead, a gene could more easily mutate to an unexpressed recessive form that can then by some mechanism alter other genes over generations to provide a more hospitable environment. I have no idea if this is true, as I have no experience in this field and am going entirely on logic- I simply find it too distracting to muddy my already-convoluted posts with disclaimers. If I am wrong, them my argument above is weakened, but not refuted.

nikipedia's avatar

@Jayne: I think I agree with your conclusion, but not a lot of your premises. Consider that the evolution of complex traits often follows non-Mendelian inheritance. (I’m kind of using big words right now to substitute in for a lot of facts and arguments I don’t know very well. Isn’t that a neat trick?)

I also wanted to comment more seriously on this:
I believe that people on the lower rungs of the economic ladder actually tend to reproduce more slowly than the wealthy.

This is decidedly untrue these days. The wealthier you are, the fewer children you tend to have: http://www.russellsage.org/chartbook/householdform/figure4.5/view

Jayne's avatar

@nikipedia, I was using the classic Mendelian model because, frankly, I would have to do a lot of research before I could truly take into account all the complexities of heredity. However, the point that I was arguing was that there is no simple, direct line between what is useful and what evolves, and Mendelian genetics serves as an adequate layman’s example for my argument. The only crucial point I drew from it was that genes are not binary values that are automatically passed on from parent to offspring, and in most cases the chance of this happening increases through moderate inbreeding (this being, of course, why extreme cases of inbreeding can be so disastrous); therefore, a small, scattered population possessing a beneficial trait is no guarantee that it will spread. The added complexities of real heredity do not, I believe, contradict this argument; they may even support it. The only point of potential conflict of which I am aware is that there is some evidence that one’s living conditions can affect one’s offspring, as Lamarck believed; however, this does not appear to have any reliable selective effect.

Umm, yeah, regarding the effect of income on reproduction, I meant to write the opposite; as it is written, the statement conflicts with the following conclusion. Thanks for the correction.

wundayatta's avatar

Every generation, they have to recalibrate IQ tests because the average person scores 120 (100 should be average). Now, that could be the result of better training and more knowledge available, but I’m inclined to thing evolution is involved.

Intelligence in women is associated with beauty (don’t make me show you the sources; I did that in another question). It seems to me that the population is getting more beautiful. Granted, that’s one person’s biased point of view. But we’re talking about belief here, and that’s my belief, and I’m sticking to it!

Jayne's avatar

(As usual, I’m not sure how seriously to take your comment, so here goes.)
Cultural evolution may be involved. Genetic evolution is certainly not. The genes controlling intelligence are vastly too complex to evolve quickly, which compounds the fact that evolution is an inconsistent process over as short a time span as one generation. So the effects at work are twofold. The first, that I.Q. tests tend to rely somewhat on knowledge, and a given piece of knowledge becomes more common and intuitive over generations, as people begin to absorb it at younger ages and with more consistency. The second, that our culture is evolving towards greater emphasis on education. I.Q. tests are presumed to test an inborn capacity, but the ability to think logically and rigorously, to force your mind through problems, is something that is learned as much as it is inherited.

wundayatta's avatar

@Jayne: I agree with your critique of the concept of IQ, and I think your explanations of the phenomena of apparently increasing intelligence are quite reasonable. However, I think it’s reasonable to believe evolution is involved, too. The articles I’ve read suggest that evolutionary adaptions can happen very quickly.

You say that: “The genes controlling intelligence are vastly too complex to evolve quickly”. You can’t prove a negative, so I’m not sure how to ask you a reasonable question here. I guess you are making a negative assertion here, so you can’t show evidence for that statement. All you can say is that we have not been able to provide evidence, so far, that fast evolution happens. I don’t know if that statement is true. More to the point, I wonder why you rule out the possibility that evolution can happen over the space of a couple of generations?

I totally agree with you that IQ is not a measurement of an inborn capacity, or, if it is, the capacity is a latent variable. IQ may or may not be one aspect of whatever it is that we might call capacity for complex thinking, or memory, or whatever else we think goes into intelligence.

It is certainly true that the ability to solve problems is something that is taught, and education may be largely responsible for it. But I ask why are we graduating more people from college? Why are job requirements requiring more education? Could it not be that there is some mental capability that is increasing over generations and that is why IQ score keeps creeping up about 20 points per generation?

I don’t know how we can separate learning from ability to learn. I think that there may be a strong relationship between architecture and function. I mean, we know that is true. Women have a different brain architecture than men, and that helps them be better, on average, on some tasks compared to men. It seems to me that it is quite possible that the structure of our brains may be changing to support our learning activities. Don’t forget, there are epigenetic changes, as well as genetic changes. Epigenetic changes can happen much more quickly, and are strongly influenced by the environment. The demand for increasing mental labor could be driving the development of increasing capacity for mental labor.

Jack79's avatar

Jayne, this is exactly where I incline more to this newer theory than traditional Darwinian evolution. I believe that faster fingers actually do increase our chances to reproduce, but also that this is not the only way evolution works.

For example, someone with a better job will have more money, which does not only affect their chances of getting married (let’s face it, access to resources has always counted for something), but also reduces the fatality rate of their offspring, since they can afford better doctors, but also simply more and better food for their children, thus better health. Then again all the kids in the Western world are dying of high colesterol, whereas millions of Asians live on fruit and veg.

Jayne's avatar

@Jack79 I suppose those factors you name do still have an effect, although they are presumably on a slow decline (and thanks, I was rather neglecting survivability of offspring); perhaps they do provide a motive for the evolution of, say, strong forearm muscles for a firm handshake, because this does have a (ridiculously high) correlation with advancement in today’s world. However, I would still maintain that the relationship between faster fingers and a better job is so incredibly tenuous and easily overshadowed by other factors (it might get you a job as a secretary, for instance, but only if you have already discovered and developed that skill, and complemented them with other necessary abilities; and nobody gets a job as a CEO because of their dazzling prowess as a typist), that if faster fingers were to evolve at all they would do so very slowly. We would certainly have noticed no difference yet (a few generations after keyboards came into use, and perhaps a dozen since factory work first presented our fingers with the task of operating delicate machinery with speed); in fact, keyboards and manual manipulation could very well be outdated by the time a significant change in the general population would have emerged.

@Daloon I am still skeptical of the idea that there could be a reliable change each generation in something so complex as intelligence (I certainly have no doubts that simpler traits more directly related to successful procreation can evolve very quickly). It would be slightly less odd if the average were simply being skewed by greater changes in a smaller portion of the population; or perhaps there is a benefit to intelligence that comes from the merging of populations allowed by modern civilization. As it is, I am inclined to attribute everything to the social factors I outlined. But having thought more deeply on the subject, I realize that I need to learn a lot more about the physiology of the brain and its dependence on genetics before I can even come up with an argument to convince myself, so I bow to your sources.

Jack79's avatar

The idea between faster fingers (and sight as opposed to say, smell) was not that it directly relates to traditional darwinian theory. What I meant was that:
1) faster fingers (eg to play videogames with) are something that we end up developing and affect social inclusion (both at early ages but also later in life). It does not directly mean that if you can’t beat someone in PES2009 you don’t get laid, but it does have an effect in how you may fit in, how many friends you have etc (think of a marginalised “nerd”).
2) All of the above eventually affects self-confidence, which does play an actual role in eventual reproduction. The relationship is tenuous, and I am in no way implying that someone who can type has a significantly higher chance of passing on genes than someone who can’t. There are millions of other factors at work. BUT, multiplied by 6 billion and over several generations, this minute difference may actually be noticeable. This is why modern humans are taller than those just a few thousand years ago.

I’d like to give an example here: I have a cousin who is hard of hearing. As recently as 50 years ago, this girl would have no social life, and practically no chance of ever finding a boyfriend, let alone get married. Today, she is a popular girl with several gold medals in sport (competing against healthy athletes, not handicapped ones), a huge network of friends who she communicates with via either the internet or her mobile, and of course a boyfriend. Technology has even allowed her to hear, enough to be able to speak when she has to. This girl does not just lead a normal life, but she’s actually better off (and with better reproductive chances) than most girls with perfect hearing. Her problem is not genetic, but if it were, it would be passed on. If she were blind however, I fear that things would be a lot harder for her, since we live in a world that depends a lot more on sight than sound.

Jayne's avatar

But the effect is not multiplied by 6 billion. The number of people who spontaneously develop the mutation will be greater, but they will still represent the same proportion of the population. So the fact that this trait has such a tenuous connection to an evolutionary advantage still means that it will develop very slowly. Assume that 1% of the population has the trait. Let us say that the trait gives an advantage of one tenth of a percent in reproduction over those without it; I feel that is an overestimate, but I have no data, of course, to base it on. By my calculations, it would be 2303 generations before ten percent of the population possesses the gene (ignoring the possibility of continued spontaneous mutation, which would speed things up a bit). So I don’t doubt that the trait can evolve; but I do doubt that it has evolved yet, because strong pressures have only existed for a dozen generations, if that, and I also have some doubts that the pressures will remain for the amount of time required.

Jack79's avatar

no you see this is where I personally disagree with traditional darwinism: I do not believe in mutation. Mutation does not explain how we are taller than our ancestors, or why we live longer and have bigger brains. Mutation would only explain a 6th finger, and even that would take many more millions of years to get established than, say, the sabertooth tiger’s teeth took to grow.

I think that every generation slowly changes as new genes (with miniscule effects) enter the gene pool while others stay out. Every generation is therefore slightly different than the next one, as opposed the mutation theory which assumes that, once every million years or so, a species “jumps” forward into the next evolutionary stage.

Jayne's avatar

Mutation does not mean that at all. A mutation is a very small change in the genes; it is the mechanism by which those ‘new genes enter the gene pool’. They aren’t introduced by some divine schedule, they are the result of small errors in the reproductive cycle of your cells producing an alteration to a gene which may or may not carry an advantage to survival; they happen very frequently- each one of us probably has mutated DNA in a few of our cells right now, but most of these mutations are entirely insignificant, and die with us (especially if the mutation makes the cell cancerous). The altered gene may cause you to be taller, it may increase the size of your brain, or it may do nothing at all. It is by no means necessarily the addition of a limb; in fact, I believe such things are often the result of conditions in the womb that have no relation to genetic mutation at all. However, where you say that ‘each generation is slightly different than the next one’, this is not the case in the way you appear to mean it. An entire population does not slowly evolve. A few people develop mutations, and these spread by a combination of luck and natural selection. If new genes, with small changes, were simply introduced to the general population, there would be no way for natural or social selection, the basis of all evolutionary theory, classic or otherwise, to work.

LostInParadise's avatar

This is my understanding as well. As to other issues raised here, I confess that this is way outside my area of expertise. The best I can do is to refer you all to the book

nikipedia's avatar

@Jack79:

I think that every generation slowly changes as new genes (with miniscule effects) enter the gene pool while others stay out.

That’s pretty much what scientists mean when they say “mutation,” so you are actually in perfect agreement with traditional evolutionary theory! I think the kind of mutant you’re thinking of only shows up in comic books. Scientists frequently create transgenic or “mutant” animals that have only one gene (or even a single nucleotide!) altered.

Jack79's avatar

then we’re all basically saying the same thing (but this is also what the book in question is saying). I was not quoting comic books though. Darwin himself seemed to have this (mis)perception.

The theory is mine btw, it’s just an estimated guess, not based on any scientific evidence, since I am not a scientist. Nor have I read any books. But I’m glad that all those scientists agree with me…they should hand me their Nobels :P

btw I never meant the whole population mutates simultaneously. Quite the opposite. But the average (height/hair colour/number of teeth) etc of the population is slightly altered with every generation.

nikipedia's avatar

@Jack79: If you’re interested, this book will teach you everything you need to know to be an expert in evolution. (It changed my life and is a big part of why I am a scientist today.)

laureth's avatar

Simple nutrition and greater access to food could account for people being taller as a whole.

Jack79's avatar

thanks Niki, though I’m probably too old for a new career. But young enough to still enjoy an “evoltionary controversy” on fluther (and tease LostinParadise’s typing skills) :)

Bedtime…see you guys tomorrow :)

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