Every year John Brockman collects essay from his friends (I want to be one) and published them on his website and in a little book [The Edge Annual Question - 2009].This year's question was, "What game-changing scientific ideas and developments do you expect to live to see?" Last year's question was, "What Have You Changed Your Mind About? Why?" The book is now out.
There are far too many answers to these questions. I usually look at a few of them but it soon becomes boring.
Sharon Begley feels the same way but she has picked out a few interesting mind changes from the 2008 question. She writes in the Jan. 3, 2009 issue of Newsweek [On Second Thought ...].
The most fascinating backpedaling is by scientists who have long pushed evolutionary psychology. This field holds that we all carry genes that led to reproductive success in the Stone Age, and that as a result men are genetically driven to be promiscuous and women to be coy, that men have a biological disposition to rape and to kill mates who cheat on them, and that every human behavior is "adaptive"—that is, helpful to reproduction. But as Harvard biologist Marc Hauser now concedes, evidence is "sorely missing" that language, morals and many other human behaviors exist because they help us mate and reproduce. And Steven Pinker, one of evo-psych's most prominent popularizers, now admits that many human genes are changing more quickly than anyone imagined. If genes that affect brain function and therefore behavior are also evolving quickly, then we do not have the Stone Age brains that evo-psych supposes, and the field "may have to reconsider the simplifying assumption that biological evolution was pretty much over" 50,000 years ago, Pinker says. How has the view that reproduction is all, and that humans are just cavemen with better haircuts, hung on so long? "Even in science," says neuroscientist Roger Bingham of the University of California, San Diego, "a seductive story will sometimes … outpace the data." And withstand it, too.There are many reasons for changing your mind about the validity of evolutionary psychology but the idea that "human genes are changing more quickly than anyone imagined" isn't one of them.
As you might have guessed, John Hawks is really happy to encourage that kind of thinking. Hawks is a proponent of the idea that genes can be fixed in the entire human population by natural selection in only a few thousand years [Recent evolution in Newsweek].
Cue misinterpretations from The Usual Suspects in 3...2...1...
ReplyDelete... men are genetically driven to be promiscuous and women to be coy, that men have a biological disposition to rape and to kill mates who cheat on them...
ReplyDeleteWhy, thats epigenetics, not 'evolutionary psychology'!
*ducks and runs*
ERV writes,
ReplyDelete*ducks and runs*
You can run but you can't hide!
But thanks, anyway, for pointing out the connection between evolutionary psychology and epigenetics.
Hehe. You guys wish...
ReplyDeleteIt's been just a couple of bad epiegentic studies like this, but I guess it's good to alert against it, anyways, like I did.
For the most, the 99.9% evo-psych is the sickness of gene-luvers, most of them angry at epigenetics and deniers of anything environmental, much like you guys.
I don't know why Larry disses evo psych if he likes James Watson and Dick Dawkins so much...yeah I remeber Dick saying we're "genetically programmed to be gullible as children"....if that isn't classic evo-psych bullshit, what is?
Evo-psych luvers are ALL dawkins fans...it's no coincidence, you know.
ReplyDeleteOK, I'm going to diss Larry now.
ReplyDeleteLarry is the kind of guy that will deny evo-psych in humans while eating up the exact way of thinking in any other kind of organism. He doesn't clearly acknowledge the fact that evo-psych is just "behavioral ecology" applied to humans. And when have you heard Larry diss behavioral ecology? he'd never do that.
Similarly, Larry will deliver post after post on the importance of genetic drift, but at the end of the day he'll be happy to accept that only natural selection explains adaptations, the evolution of eyes,ears, beaks, etc...just like Alen Orr. His concern is anecdotal at best. When have you heard Larry explain the role of exaptation in the origin of complex adaptations? When has he fairly presented the views of structuralists, who see development as the creative force, selection the mere constraint? All he ever does is dismiss development. All he can think about is genes and their frequency changes by drift or selection. Pretty goddam narrow....
He's just an old biochemist who likes to fight superstition and creationism, but he hasn't got his evolutionary biology straight, not by far. Even though he thinks he does, of course. Actually, he's ideological and ignorant.
On his behalf, many "evolutionary biologists" by training can be very ideological and ignorant, too
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteI think the point of my post (always somewhat in doubt, of course) is that recently selected genes will be variable in humans, not fixed.
ReplyDeleteSince a number of human populations have been isolated during the last 10,000 years or more, there is no chance that a selected gene could have fixed during the "last few" thousand.
John Hawks says,
ReplyDeleteI think the point of my post (always somewhat in doubt, of course) is that recently selected genes will be variable in humans, not fixed.
I understand. You explain it very well at Why human evolution accelerated.
Since a number of human populations have been isolated during the last 10,000 years or more, there is no chance that a selected gene could have fixed during the "last few" thousand.
OK, so maybe "few" thousand gives the wrong impression. Your diagrams in the posting quoted above suggest that fixation can occur in 20,000 years.
I think I understand your main point. Correct me if I'm wrong.
You think that there was a time about 50,000 years ago when humans were not evolving by positive natural selection. That's because humans were close to their adaptive optimum.
Beginning about 40,000 years ago, according to you, the environment began to change as humans began to settle down and form cities. This has lead to a rapid increase in adaptive evolution.
Here's the relevant part from your posting (referenced above).
Still, a very small fraction of the mutations in any given population will be advantageous. And the longer a population has existed, the more likely it will be close to its adaptive optimum -- the point at which positively selected mutations don't happen because there is no possible improvement. This is the most likely explanation for why very large species in nature don't always evolve rapidly.
Instead, it is when a new environment is imposed that natural populations respond. And when the environment changes, larger populations have an intrinsic advantage, as Fisher showed, because they have a faster potential response by new mutations.
From that standpoint, the ecological changes documented in human history and the archaeological record create an exceptional situation. Humans faced new selective pressures during the last 40,000 years, related to disease, agricultural diets, sedentism, city life, greater lifespan, and many other ecological changes. This created a need for selection.
Larger population sizes allowed the rapid response to selection -- more new adaptive mutations. Together, the the two patterns of historical change have placed humans far from an equilibrium. In that case, we expect that the pace of genetic change due to positive selection should recently have been radically higher than at other times in human evolution.
Is this still a fair representation of what you believe?
Evolutionary psychology: for academics who don't understand evolution but manage to make a living talking about it anyway.
ReplyDeleteWhy is Vargas calling Richard Dawkins "Dick"?
ReplyDeleteYou think that there was a time about 50,000 years ago when humans were not evolving by positive natural selection. That's because humans were close to their adaptive optimum.
ReplyDeleteBeginning about 40,000 years ago, according to you, the environment began to change as humans began to settle down and form cities. This has lead to a rapid increase in adaptive evolution.
More or less. Fisher's argument about adaptation is that positive selection should be rare in most natural populations, because they have been living in their current environments for so long that they should be close to optimal. This doesn't mean that new selected mutations couldn't happen in principle, just that they should be rare.
We posit a twofold effect for humans. First, there are a lot more of us than there were 50,000 years ago, so the population should have a much higher incidence of mutations that are intrinsically rare.
For instance, humans 50,000 years ago were almost certainly language-users, and probably had been for a long time. But mutations that improved fitness due to their effect on language may still have been possible, even if rare, and would therefore be more likely in the later, larger population.
Second, the ecology of some human populations changed markedly, with agriculture and cities, sure, but also earlier (pre 10,000-year ago) events like moving to higher latitudes. So there's no reason to expect that human mean fitness should be optimized in these new environments. Humans 50,000 years ago may have had any number of lactase persistence mutations, but selection did not favor them until after 8000 years ago.
The net effect should be diversity-generating in the short run. In the long run, selected genes that do not come to a balance will proceed to fixation.In a human population, that process takes on the order of 500 generations or longer depending on the strength of selection.
In practice, different alleles might be positively selected in different populations for the same function -- that seems to be the case of skin color alleles in Europeans and Asians, or malaria resistance in Africans and Southeast Asians -- and the frequency evolution of any particular allele will eventually depend on the geographic distribution of the others.
Your diagrams in the posting quoted above suggest that fixation can occur in 20,000 years.
Sure. That's just math, assuming a W-F model. But that's within a panmictic population. We used that unit because we were considering individual populations (CEU, YRI, etc.) where it might not be such a bad approximation. But for humans you always have to remember places like Australia, where a small fraction of the human population had little gene flow with Asia for 30,000 years.
John Hawks,
ReplyDeleteMore or less. Fisher's argument about adaptation is that positive selection should be rare in most natural populations, because they have been living in their current environments for so long that they should be close to optimal.
Is this what you believe?
Do you believe that most species have reached the point where they are so well adapted to their environment that almost all new mutations will be either neutral or detrimental?
Could you identify a few of these species for me? How about picking out one example of a flowering plant, one example of a mammal, and one example of bacterial species that have reached this optimal state?
To me the idea that a modern species could be optimally adapted to its present environment seems totally contrary to my view of evolution.
Question for John Hawks: What does the rate of evolution by positive selection look like in a) other primates, b) other mammals, c) other vertebrate orders, d) other phyla? Are humans the only one with a profile of acceleration in the last 40-50K? If you are correct such a pattern should only occur in species highly impacted by humans during this period (like domesticates, parasites, game species). Others might show more recent acceleration with ecological pressure, or in sync with human migrations and population expansion.
ReplyDeleteUnless the pattern of acceleration is some kind of artifact.
Tupaia
Do you believe that most species have reached the point where they are so well adapted to their environment that almost all new mutations will be either neutral or detrimental?
ReplyDeleteI think most species, most of the time, are at a point where fitness-increasing mutations of large effect are unlikely.
As for whether almost all mutations are neutral or detrimental, I would instead say that almost all mutations of large effect are either neutral or detrimental. Since both the fixation probability and fixation rate of advantageous mutations are linear functions of the effect size, this means that further adaptation by positive (and directional) selection must become slower and slower, assuming constant environment and population size.
To me the idea that a modern species could be optimally adapted to its present environment seems totally contrary to my view of evolution.
I see no contradiction between your view and the observation that adaptive mutations should be more likely in species that have undergone recent large changes in size or environment.
Question for John Hawks: What does the rate of evolution by positive selection look like in a) other primates, b) other mammals, c) other vertebrate orders, d) other phyla? Are humans the only one with a profile of acceleration in the last 40-50K?
ReplyDeleteUnfortunately, we have data to evaluate this only in humans and a few domesticates. Maize has a pattern much like ours. We find it very interesting that the selection we've experienced ourselves is comparable to what we have done to corn in the last 10,000 years.
We are able to use phylogenetic comparisons of single genomes to get a picture of the rate of positive selection on different primate lineages. There is no indication on any lineage, including our own, that the rate of positively selected substitutions has been anywhere near the rate of apparent positively selected mutations in humans in the last 40,000 years. Those comparisons are in our 2007 paper.
If you are correct such a pattern should only occur in species highly impacted by humans during this period (like domesticates, parasites, game species). Others might show more recent acceleration with ecological pressure, or in sync with human migrations and population expansion.
We agree. This is a logical test of our hypothesis. Also, a comparison with any ancient human genome, such as the Neolithic Iceman, would show the lack of adaptive variants that are now common. We do have these data for a very small number of genes - lactase is the best example.
Unless the pattern of acceleration is some kind of artifact.
I think if we compared a species with a 1000-fold recent increase in numbers to a species without any increase, and found that they showed the same pattern of positive selection, that would be extremely interesting. In that sense, our hypothesis is the null, and rejecting it would really challenge the synthetic theory.
Well, I know John Hawks thinks he's too good to talk to me...but anyways.
ReplyDeleteJohn, how many "talking genes' do you think Koko the gorilla or Mike the Bonobo sprouted when they learned to talk in sign language?
Would'nt you say that cultural environment had some role in the origin of language? o was this just a matter of awaiting for the right muation to come along?
Interesting, Dr. Hawks.
ReplyDelete"if we compared a species with a 1000-fold recent increase in numbers to a species without any increase, and found that they showed the same pattern of positive selection, that would be extremely interesting"
I hate to get ahead of the data but if such a pattern were found here's a possible explanation: Perhaps there are high rates of fluctuating selection of mutations within periods of magnitude 100 or 10 K but over millions of years the rate of selection is characterized by gradualism or stasis (kind of like how the Dow Jones market can have high intraday volatility but end the week in the same place it started).
Maybe much of that high rate of selection for mutations be the result of intragenomic conflict (meiotic drive etc) rather than selection based on the mutant allele's phenotypic correlates (physiology, behavior, morphology).
It might be the case that mutations undergo high rates of selection due to intragenomic conflict in the short term but over longer periods gradualism or stasis prevails, reflective of selection based on phenotype.
That might be a minor wrinkle on the synthesis. But I'm just speculating.
Tupaia
Well, I know John Hawks thinks he's too good to talk to me...but anyways.
ReplyDeleteDon't know why you'd assume that...
John, how many "talking genes' do you think Koko the gorilla or Mike the Bonobo sprouted when they learned to talk in sign language?
Probably about the same as the number of lactase persistence alleles that they would sprout given regular milkshakes. None.
On the other hand, if we set up a relationship between fitness and signing in bonobos and kept it that way for many generations, many standing variants would change in frequency, and there would be some chance of a new mutation doing so as well.
Would'nt you say that cultural environment had some role in the origin of language? o was this just a matter of awaiting for the right muation to come along?
Selection for genes that increase language-capacity requires a correlation between language-capacity and fitness. The most plausible cause of such a correlation is the cultural environment.
If you are interested, you should read Pinker's work on language evolution, such as Pinker and Bloom 1990.
http://www.bbsonline.org/Preprints/OldArchive/bbs.pinker.html
Pinker? Ouch!
ReplyDelete"Evolutionary theory offers clear criteria for when a trait should be attributed to natural selection: complex design for some function, and the absence of alternative processes capable of explaining such complexity. Human language meets this criterion"
That is a remarkably ideological answer. Complex "design" is never the result of selection alone: to blame it all on selection is just the perpetuation of a very old anti-paleyan rethoric. Actual documentation of the evolution of complex design can hardly be said to "show" natural selecction been responsible for everything. There's a lot of swinging on your woden horse in that kind of statement... the second part is specially telling..."the absence of alternative processes capable of explaining such complexity". Obviosuly, Pinker cannot accept the role of anything else but selection in the origin of complex "design". This is just awful silly. Pure ideology.
Of course, what can we expect form the man that will echo phrases such as "the nature-nurture debate is over"? That may fly among psychologists, but it will juts produce chuckles among biologists even vaguely familar with the complexities of the genotype-phenotype relationship.
as I said, many 'evolutionary scientists" are very idelogical and thus, very ignorant. They've got it all figured out already, huh
About language genes, I think it's necessary for you to make the distinction between environment as a sieve (.i.e only as agent of selection) and environmnt as a phenotype modifier. The correct analogy is that, without lactase persistence genes, I can feed on milkshakes and avoid diarrhea thanks to phenotypic plasticity.
ReplyDeleteNotice waht I'm saying: without this DIRECT influence of environment, the "language mutation" is not simply "not advanatageous".
It would probabaly have no effect on the phenotype. The effect of genes on phenotype is context-dependendent. Pinker does not quite realize this.
the second part is specially telling..."the absence of alternative processes capable of explaining such complexity". Obviosuly, Pinker cannot accept the role of anything else but selection in the origin of complex "design". This is just awful silly. Pure ideology.
ReplyDeletePinker's formulation seems entirely reasonable to me. A snowflake has a complex design. This might conceivably be due to selection on snowflakes, but we in fact have an alternative physical process to explain it.
Possibly such physical explanations will be found for human language -- Michael Tomasello's research tends toward this conclusion for many aspects of human language and culture. In fact, Pinker and Bloom in the cited article (1990) consider the environment in some detail -- this is the point of their discussion of the "Baldwin effect."
The correct analogy is that, without lactase persistence genes, I can feed on milkshakes and avoid diarrhea thanks to phenotypic plasticity.
As can bonobos. But this plasticity does not extend to the caloric extractive potential of digestive systems that continue to generate lactase at juvenile levels. Nor does the plasticity of bonobo brains extend to the grammar-learning potential of most humans.
Observing that culture is not a sufficient explanation is not the same as saying it is not necessary.
"Pinker's formulation seems entirely reasonable to me"
ReplyDeleteI'm sorry to hear that
"A snowflake has a complex design. This might conceivably be due to selection on snowflakes, but we in fact have an alternative physical process to explain it"
Yipes! Your case is worse than I thought.
First of all, no, selection does not in itself explain complexity. You only will have complexity if the mechanism of variation has something about it that increases complexity.
To say that NS just in itself creates complexity you haveto abide by some pretty old progressist notions of how natural selection works that are very ideological and nothing empirical.
I am hoping for your own sake that you would not seriously consider natural selection to be a plausible explanation for the complexity of snowflakes... It never would, in my opinion. There's a reason why selection is not an intrinsic part of, say thermodynamics (even if some have tried to drw baseless and cheesy analogies)
Selection is a relevant to the direction taken by evolution but it is no spontaneous cobbler of adaptive complexity. You actually need quite more than selection to explain complexity. That's simply a myth, mostly perpetuated by those who think we need it to fight creationism. But it's not science, it's ideology.
You cabn tel this yourself when you accept culture is necessary for the evolution of human language. Sure, mutations and selection are necessary too. But they do not on their own explain the evolution of language. That should be enough for you to realize that selection alone does not explain the evolution of this adaptive, complex trait.
Now, what's worse is that you seize on this myth as some kind of default explanation that must be accepted in absence of an alternative. But guess what: why should you even loom so hard for an alternative, if you already dispose of such a nice "scietnific" (actually, ideological) explanation? Selection did it!!
I'll tell you where I've heard exactly that kind of thinking before. From theists. They have seriously argued to me that god is the explanation we must accept, in absence of an alternative. But of course, the problem there is that already you have some kind of explanation. This stops you from searching for an alternative. Thinking this way is the stuff of science-stoppers. If anything selection used this way is worse because its supposed to be "scientific".