We see study after study of genes 'for' behavioral traits considered to be driven by selection: intelligence, athletic ability, criminality, recklessness, drug abuse, aggression, even being a caring grandmother. The list goes on and on and on. Simplistically stated, the idea is that behavioral traits have a genetic basis, usually a simple 'genetic' one, and that during human evolution, those genetically bestowed with the 'best' version of the trait outcompeted those unlucky enough to be less intelligent, less of a risk taker, a more fearful warrior, and so on. That is pure Darwinian determinism: the bearers of the 'optimal' version of a trait systematically had more offspring, and thus the gene(s) for that version were selected for, and therefore increased in frequency.
This is why, for example, the basis of homosexuality is so curious to evolutionary biologists. How could a behavioral trait that means its bearer does not have offspring ever have evolved? How could a gene persist if it codes for something that interferes with reproduction so the gene isn't passed on? The most common explanation for this is that during the long millennia of human evolution, homosexuals mated and reproduced anyway, because homosexuality was culturally proscribed in the small groups in which humans lived. Maybe that's so, but it's certainly no longer true in many cultures where being gay doesn't have to be hidden anymore, so should we now expect the frequency of homosexuality to fall? Another post hoc account is that homosexuals helped care for their relatives' children, enhancing their extended kinship and hence consistent with natural selection--a technically plausible but basically forced speculative explanation by those who want Darwinian determinism to be as universal as gravity.
In any case, the "cause" of homosexuality is certainly an interesting evolutionary puzzle, if it's assumed to be genetic. It may well not be, of course -- perhaps sexual orientation is influenced by environmental exposures in utero or in infancy. But, let's go with the genetic assumption. Let's even assume that looking for genes for IQ, aggression and so many other behaviors is reasonable, because all these traits, as all traits, must be here because of natural selection.
In that case, it's very curious that there are so many traits that defy Darwinian explanation whose genetic basis isn't being explored. Where are the searches for genes for, say, voluntary celibacy, or use of birth control and non-celibates choosing not to have children, or for suicide, or child-beating, or infanticide, or abortion, or young men volunteering to be soldiers? These are all traits that make no evolutionary sense and shouldn't have evolved, if such traits have a genetic basis. We should be just as perplexed by the evolutionary history of these behaviors as we are by homosexuality. Why aren't we looking for genetic explanations?
I think it's a reflection of cultural values. It's rather akin to environmental epidemiologists never looking for the harmful effects of cauliflower, broccoli or Brussel's sprouts -- instead it's the things we like, our indulgences; alcohol, fatty foods, sugar, which reflect our Puritan scorn for pleasure. I think we notice and think about what seem to us to be unacceptable aberrations, and give much less thought to what seems normal. It's ordinary to us that nuns and priests choose not to reproduce, even if that is completely non-Darwinian, or that suicide bombers are generally of reproductive age and are foregoing having children. Abortion may not be personally acceptable to you, but it's a societal norm. Indeed, artificial birth control itself is highly problematic in a Darwinian world -- even worse for Darwinian theory, it sends women into the work force, away from their children.
Apparently we don't generally notice that these 'normal' behaviors are non-Darwinian -- our primary drive, consciously or unconsciously, but inherently, is supposed to be to perpetuate our genes. If behaviors are genetically driven, selected for, then it's not just homosexuality -- which, until recently, was not socially acceptable -- that doesn't make evolutionary sense, it's any behavior whose primary ramification is not to send our genes into the next generation.
So, don't we have the same issue with explaining the evolutionary origin of all these behaviors as we do explaining homosexuality? Perhaps. But let's consider an explanation that's not generally proffered: Perhaps this is all just statistical 'noise' around a weak rather than precisely or strongly deterministic natural selection, that Nature is just sloppier than the strictly Darwinian view would expect. The success of no species requires that every individual reproduce, so long as enough do. Culture is a powerful force -- once we respond to cultural dictates and norms, the simple evolutionary explanation of selection for optimal (in fitness terms) traits is much less convincing. And, perhaps we didn't evolve to reproduce, just to have orgasms.
And, is there a gene for being dogmatic?
Showing posts with label Darwinian determinism. Show all posts
Showing posts with label Darwinian determinism. Show all posts
Friday, January 11, 2019
Tuesday, September 4, 2012
Living the life of Reilly...and lots of it!!
The science of 'aging' research has had its ups and downs, probably more downs than ups in a particular sense. Aging researchers (that is, researchers on aging) have wanted their field to be a real science with some theory, some magic law-like explanations. Theories have ranged from body size and metabolic rates specifying some 'maximum lifespan potential', to chromosome ends or a gene related to them (telomerase), to a specified tradeoff between being healthy when young and paying for it by aging, and more. Behind many if not most such theories is the darwinist idea that lifespan is prescribed by some specific adaptive advantage, with humans being exceptional.
But these haven't really worked (even if aging researchers, that is, researchers who have been aging over recent decades as one theory after another has faded), and one might think this was a dead-end area, so to speak.
One of the magical theories, of long-standing, has been that caloric restriction leads to an organism not burning itself out too quickly, and lasting longer. It was once believed that mammals and some birds were endowed with a certain number of heart-beats, or calories burned, and that this could explain the typical lifespans of different species. Body and/or brain size were thought to be correlated with these metabolic variables. As it turns out, and contrary to widespread mythology, even among professionals, we humans are barely--if at all--exceptional. And some real exceptions were found, such as some very long-lived birds and tortoises.
However the idea lived on because of experiments in laboratory rodents that showed that restriction in calories consumed led to longer lifespans on average. There was then some preliminary suggestion that this held true for primates--rhesus monkeys, one of the practical preferred primate for such work, in particular. Alas, living in privation (look at the faces on these poor animals; shouldn't the Institutional Review Board have prevented this study?) has failed over a long study time now, to show the effect. I saw this in the NYT, though it's everywhere, but have not yet read the primary report.
This means that within reason at least we can live the life of Reilly--eat, drink, and be merry! And still have our allotted time. Well, up to a point....
Fortunately for science, if unfortunately for aging researchers and their simple theories, we really do have reasonable, if general and non-specific, non-selectionistic explanations. There are many ways to go, and we die not because of a single aging clock, but because we statistically run out of the chance of avoiding all causes of death. It only takes one to get you. Now, there certainly does seem to be some general programming of our life-history, since our time to adulthood and so on is certainly associated with our body size, and this is generally true among mammals. Thus, there must be some genetic basis for these characteristics. But it need not be a single basis. If there were advantage to being bigger and that led to living longer (perhaps to be able to raise offspring to their maturity, or for some other reasons) then any mechanisms that led to that would have been supported by selection.
That accounts in a very generic way for our body size and the general longevity associated with it. But that fact does not suggest a simple calibration of lifespan (that is, death). Despite some factors that do statistically increase some risks, what we die of is very variable from person to person, involving all body systems. While there is a rough, body-size correlated calibration of all of this in some way, what ends life is not a death program, but the gradual running-out of the probability of escaping all causes, as we noted above. This is the 'competing causes' phenomenon of our lifespans.
There is no single death gene. The theories and their evolutionary explanations never had any serious scientific backing, despite decades of being proffered to the profession, the public, and the NIH funders. I know this, because I and others have been pointing out the counter arguments roughly presented above for decades. But the reasoning and the data to support it were not convenient for those seeking for simple explanations.
Whatever calibrates our life-histories (including some of the suggested mechanisms as part of the story, as mentioned above), we still don't know. But if we are conveniently prone for self-serving reasons to accept this latest study of rhesus monkeys, we can feel free now to go pop a cold one, and open that bag of chips!
But these haven't really worked (even if aging researchers, that is, researchers who have been aging over recent decades as one theory after another has faded), and one might think this was a dead-end area, so to speak.
One of the magical theories, of long-standing, has been that caloric restriction leads to an organism not burning itself out too quickly, and lasting longer. It was once believed that mammals and some birds were endowed with a certain number of heart-beats, or calories burned, and that this could explain the typical lifespans of different species. Body and/or brain size were thought to be correlated with these metabolic variables. As it turns out, and contrary to widespread mythology, even among professionals, we humans are barely--if at all--exceptional. And some real exceptions were found, such as some very long-lived birds and tortoises.
 |
| NIH Nat'l Inst of Aging; NYT |
For 25 years, the rhesus monkeys were kept semi-starved, lean and hungry. The males’ weights were so low they were the equivalent of a 6-foot-tall man who tipped the scales at just 120 to 133 pounds. The hope was that if the monkeys lived longer, healthier lives by eating a lot less, then maybe people, their evolutionary cousins, would, too. Some scientists, anticipating such benefits, began severely restricting their own diets.
The results of this major, long-awaited study, which began in 1987, are finally in. But it did not bring the vindication calorie restriction enthusiasts had anticipated. It turns out the skinny monkeys did not live any longer than those kept at more normal weights. Some lab test results improved, but only in monkeys put on the diet when they were old. The causes of death — cancer, heart disease — were the same in both the underfed and the normally fed monkeys.Too bad! Or is it?
This means that within reason at least we can live the life of Reilly--eat, drink, and be merry! And still have our allotted time. Well, up to a point....
Fortunately for science, if unfortunately for aging researchers and their simple theories, we really do have reasonable, if general and non-specific, non-selectionistic explanations. There are many ways to go, and we die not because of a single aging clock, but because we statistically run out of the chance of avoiding all causes of death. It only takes one to get you. Now, there certainly does seem to be some general programming of our life-history, since our time to adulthood and so on is certainly associated with our body size, and this is generally true among mammals. Thus, there must be some genetic basis for these characteristics. But it need not be a single basis. If there were advantage to being bigger and that led to living longer (perhaps to be able to raise offspring to their maturity, or for some other reasons) then any mechanisms that led to that would have been supported by selection.
That accounts in a very generic way for our body size and the general longevity associated with it. But that fact does not suggest a simple calibration of lifespan (that is, death). Despite some factors that do statistically increase some risks, what we die of is very variable from person to person, involving all body systems. While there is a rough, body-size correlated calibration of all of this in some way, what ends life is not a death program, but the gradual running-out of the probability of escaping all causes, as we noted above. This is the 'competing causes' phenomenon of our lifespans.
There is no single death gene. The theories and their evolutionary explanations never had any serious scientific backing, despite decades of being proffered to the profession, the public, and the NIH funders. I know this, because I and others have been pointing out the counter arguments roughly presented above for decades. But the reasoning and the data to support it were not convenient for those seeking for simple explanations.
Whatever calibrates our life-histories (including some of the suggested mechanisms as part of the story, as mentioned above), we still don't know. But if we are conveniently prone for self-serving reasons to accept this latest study of rhesus monkeys, we can feel free now to go pop a cold one, and open that bag of chips!
Wednesday, April 27, 2011
Care....and be smart! Is it in your genes?
A new article in the 'early edition' of PNAS suggests that IQ tests are not so simply interpretable as some might believe, or wish. Duckworth et al. ('Role of test mutation in intelligence testing') show that not just the raw DNA in a person, or his/her environmental circumstances such as diet and books in the house, but also motivation affect both the score and the usefulness of the test in predicting life success.
The authors studied 2008 individuals and found substantial increases in IQ test scores by highly motivated participants, greater for those with lower baseline scores. IQ scores predicted many aspects of life outcomes, but basically not after motivation in taking the test was taken into account.
No matter how you may feel about the Nature-Nurture debate in regard to intelligence, this paper is yet another example of the complexities of biological causation. In itself, it's probably a minor study relative to the larger question of how much of what an organism is, is 'inherited' in its genome, and how much is due to many other factors of its life-experience. The authors themselves temper their interpretation.
However, the relevance to societal issues is great, since much in your life depends on how well you fit into the system that assigns resources and rewards, and because discrimination, positive and negative, results. This affects your social 'fitness' and one can debate if it affects your evolutionary fitness. But the question goes far beyond the political.
If organisms can be predicted from their genomes, then environments don't count much. That is relevant to GWAS and personalized medicine, of course, but also to evolution itself. If genomes are predictive we can effectively forestall disease. That would be good (though it's largely not true).
But what about evolution? The idea of evolution in the adaptive Darwinian sense is that genomes are predictive in the context of the environment! That is what adaptation is all about--adaptation to the environment. It is those genomes that, in their environmental context, proliferate the most.
This at its very core means that genomes cannot in themselves be predictive. Or, put another way, adaptive Darwinian evolution can only occur to the extent that genomes are not predictive of the organism's traits. In this sense, genomes evolve as respondents, not determinants. In a static environment genomes might become predictive, or seem predictive, but that would be because of the environment, not in spite of it.
The politics of IQ testing and its many, sometimes evil, heads is not our point here. Again, we just take this story as an illustration of the elusiveness of biological causation, and the subtlety of the Nature-Nurture phenomenon.
The authors studied 2008 individuals and found substantial increases in IQ test scores by highly motivated participants, greater for those with lower baseline scores. IQ scores predicted many aspects of life outcomes, but basically not after motivation in taking the test was taken into account.
No matter how you may feel about the Nature-Nurture debate in regard to intelligence, this paper is yet another example of the complexities of biological causation. In itself, it's probably a minor study relative to the larger question of how much of what an organism is, is 'inherited' in its genome, and how much is due to many other factors of its life-experience. The authors themselves temper their interpretation.
However, the relevance to societal issues is great, since much in your life depends on how well you fit into the system that assigns resources and rewards, and because discrimination, positive and negative, results. This affects your social 'fitness' and one can debate if it affects your evolutionary fitness. But the question goes far beyond the political.
If organisms can be predicted from their genomes, then environments don't count much. That is relevant to GWAS and personalized medicine, of course, but also to evolution itself. If genomes are predictive we can effectively forestall disease. That would be good (though it's largely not true).
But what about evolution? The idea of evolution in the adaptive Darwinian sense is that genomes are predictive in the context of the environment! That is what adaptation is all about--adaptation to the environment. It is those genomes that, in their environmental context, proliferate the most.
This at its very core means that genomes cannot in themselves be predictive. Or, put another way, adaptive Darwinian evolution can only occur to the extent that genomes are not predictive of the organism's traits. In this sense, genomes evolve as respondents, not determinants. In a static environment genomes might become predictive, or seem predictive, but that would be because of the environment, not in spite of it.
The politics of IQ testing and its many, sometimes evil, heads is not our point here. Again, we just take this story as an illustration of the elusiveness of biological causation, and the subtlety of the Nature-Nurture phenomenon.
Monday, November 1, 2010
Genes for how we think and what we think
Several people have sent us the latest genetics of political science story that has been getting attention all over the web (e.g., here and here). The paper referred to in these stories just appeared in The Journal of Politics with the title, "Friendships Moderate an Association between a Dopamine Gene Variant and Political Ideology." People become liberal, the authors claim, if they've got a particular variant of the "novelty seeker gene", DRD4, and had a lot of friends in high school.
This is a follow-up to a 2007 paper by two of the same authors, Fowler and Dawes, reporting two genes that predicted voter turnout in twin studies, although these genes are also moderated by environment, they say; turnout depends on the association between genes and exposures to religious social activity. They conclude that these findings are important to "how we both model and measures political interactions."
And a follow-up to a 2009 paper reporting the gene for partisanship and joining of political groups (the DRD4 gene again). Among other papers.
Now, these are only a few of the authors responsible for the recent large crop of papers reporting genes for voting behavior and political ideology and other behaviors in the realm of political science, but they are particularly visible, and publishing the latest paper just before the November elections -- gee, wonder why -- certainly helps. The headline in the Fox News story about this work is "Researchers find the liberal gene", and they then go on to say that "liberals can't help themselves, it's in their genes".
OK, let's stick with this for a minute. Much as we wanted to, we couldn't ignore what's below the headlines, the meat of the piece:
And, "...political ideology has been a part of us for tens of millions of years"? "These are processes that have been going on for the past million years"? Let's see, Homo sapiens dates from when? 100-200 thousand years ago? Were our Homo erectus ancestors liberals or Tories? Being liberal sometimes and conservatives others is what allowed our species to survive? Who knows what that could even mean. And of course Fox News picks up on the idea that natural selection didn't make us all liberal, now did it? No it didn't, because it didn't make sense.
So, if political ideology is genetic, there must be a gene for conservatism too? In which case, why do we see the kinds of swings in voting patterns in the US that we have seen in the last several decades, and are likely to see this week? It can't be that it's primarily those who are genetically programmed to be liberal who vote in some elections, and those who are conservative who vote in others. People actually do change their minds. Oh, there must be a gene for that, too.
But much more important than these silly quotes, or even than the details of the paper, this paper is an indication of the use and abuse to which genetic data are currently being put. In a day or two we'll write about the data set that this study was actually based on but for now let's think about what it means to even ask whether there are genes for voting behavior. (And, by extension, if how you vote is due to gene by environment interaction, and in this case, the 'environment' is the number of friends a teenager has in high school, couldn't it be that there's a gene for the number of friends we have? Well, it won't be a surprise to hear that the answer is yes if you believe studies done with the same National Longitudinal Study of Adolescent Health -- paid for with your tax dollars -- used in the latest Fowler paper.)
It isn't irrelevant to ask who wants to know, who's asking about genes for behavior. Or why they find these kinds of questions so interesting. Or whether this kind of science should just be smiled at tolerantly even if it's bogus. Or what we should think to do, at this stage and before it's too late, if it happens to be correct.
There are many issues here, and they involve the spectrum of things from personal politics (ours, the investigators, and yours), the nature of legitimate science, of criteria for scientific inference, of vested interests, of politics, of ideology and tribalism and much more.
One thing is clear. Like it or not, this search for genes for traits related to how we behave, or for how well we think and even for what we think, is a wave, perhaps a tidal wave, of a kind of Darwinian determinism sweeping across the political spectrum, led by the United States but (as so often happens) with followers in Europe and Asia (mainly these days, China). It is not idle, ivory tower science. Whether it is yet another passing fancy, or something more serious, time will tell. But for many reasons, this like other aspects of genetic determinism these days is not going to be changed because of the facts: it is a commitment, and taxpayers are going to be paying for it for a long time to come, for better or worse.
This is a follow-up to a 2007 paper by two of the same authors, Fowler and Dawes, reporting two genes that predicted voter turnout in twin studies, although these genes are also moderated by environment, they say; turnout depends on the association between genes and exposures to religious social activity. They conclude that these findings are important to "how we both model and measures political interactions."
And a follow-up to a 2009 paper reporting the gene for partisanship and joining of political groups (the DRD4 gene again). Among other papers.
Now, these are only a few of the authors responsible for the recent large crop of papers reporting genes for voting behavior and political ideology and other behaviors in the realm of political science, but they are particularly visible, and publishing the latest paper just before the November elections -- gee, wonder why -- certainly helps. The headline in the Fox News story about this work is "Researchers find the liberal gene", and they then go on to say that "liberals can't help themselves, it's in their genes".
OK, let's stick with this for a minute. Much as we wanted to, we couldn't ignore what's below the headlines, the meat of the piece:
"Ideology is about 40 percent heritable. It's almost half genes and half environment," Fowler told FoxNews.com. What's more, he said, any trait that can be inherited has potentially been with the human race for a long time, meaning political ideology has been a part of us for tens of millions of years.
"If it's really the case that genetic variation is influencing ideology, this isn't something we've been living with for the last ten years," he told FoxNews.com. "These are processes that have been going on for the past million years."
Fowler suggests that it made more sense to be liberal in certain environments at specific points in human history, and in others a conservative ideology was merited. "And this is what made it possible for our species to survive," he said.
"If it made sense for us all to be liberal, natural selection would have made us all liberal."There's so much wrong here, and if the quotes are accurate, it's Fowler who's wrong, not the journalist. Fowler may 'know' that DRD4 is a dopamine receptor gene, the receptor for a neurotransmitter, and he may think that political ideology is a result of gene by environment interaction, but the Fox story suggests that he believes he's found a gene 'for' liberalism (in spite of the sentence in the paper itself that rightly cautions that "perhaps the most valuable contribution of this study is not to declare that ‘‘a gene was found’’ for anything, but rather, to provide the first evidence for a possible gene-environment interaction for political ideology"). Emics and etics -- what he says is not what he does.
And, "...political ideology has been a part of us for tens of millions of years"? "These are processes that have been going on for the past million years"? Let's see, Homo sapiens dates from when? 100-200 thousand years ago? Were our Homo erectus ancestors liberals or Tories? Being liberal sometimes and conservatives others is what allowed our species to survive? Who knows what that could even mean. And of course Fox News picks up on the idea that natural selection didn't make us all liberal, now did it? No it didn't, because it didn't make sense.
So, if political ideology is genetic, there must be a gene for conservatism too? In which case, why do we see the kinds of swings in voting patterns in the US that we have seen in the last several decades, and are likely to see this week? It can't be that it's primarily those who are genetically programmed to be liberal who vote in some elections, and those who are conservative who vote in others. People actually do change their minds. Oh, there must be a gene for that, too.
But much more important than these silly quotes, or even than the details of the paper, this paper is an indication of the use and abuse to which genetic data are currently being put. In a day or two we'll write about the data set that this study was actually based on but for now let's think about what it means to even ask whether there are genes for voting behavior. (And, by extension, if how you vote is due to gene by environment interaction, and in this case, the 'environment' is the number of friends a teenager has in high school, couldn't it be that there's a gene for the number of friends we have? Well, it won't be a surprise to hear that the answer is yes if you believe studies done with the same National Longitudinal Study of Adolescent Health -- paid for with your tax dollars -- used in the latest Fowler paper.)
It isn't irrelevant to ask who wants to know, who's asking about genes for behavior. Or why they find these kinds of questions so interesting. Or whether this kind of science should just be smiled at tolerantly even if it's bogus. Or what we should think to do, at this stage and before it's too late, if it happens to be correct.
There are many issues here, and they involve the spectrum of things from personal politics (ours, the investigators, and yours), the nature of legitimate science, of criteria for scientific inference, of vested interests, of politics, of ideology and tribalism and much more.
One thing is clear. Like it or not, this search for genes for traits related to how we behave, or for how well we think and even for what we think, is a wave, perhaps a tidal wave, of a kind of Darwinian determinism sweeping across the political spectrum, led by the United States but (as so often happens) with followers in Europe and Asia (mainly these days, China). It is not idle, ivory tower science. Whether it is yet another passing fancy, or something more serious, time will tell. But for many reasons, this like other aspects of genetic determinism these days is not going to be changed because of the facts: it is a commitment, and taxpayers are going to be paying for it for a long time to come, for better or worse.
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