I. There are a few books I’ve read recently that make the case that when it comes to nature versus nurture, nature is pretty much winning. Take this paragraph from Geoffrey Miller’s The Mating Mind (a book I very much recommend): Our bodies are rich sources of evidence about sexual selection pressures because they are visible, measurable, easily comparable with those of other species, and relatively undistorted by human culture. In recent years much nonsense has been written by post-modern theorists such as Michel Foucault about the "social construction of the body," as if human bodies were the incarnation of cultural norms rather than ancestral sexual preferences.
Who do you consider to be in the "genes are all that matter" crowd?
When environments are very similar, genes will account for almost all differences. When genes are very similar, environment will determine almost all differences. There is no fixed ratio.
I continue to think that Simon Blackburn's review of Pinker's The Blank State (https://swb24.user.srcf.net/reviews/Pinker.htm) is the best take on the whole 'nature versus nurture' framework - I think he pretty persuasively shows that the whole 'debate' is confused. Very much worth a read.
Caplan's book is a good example, because he has completely broken down the nature/nurture distinction: on his analysis, rather than genes being opposed to culture, *both* genes *and* culture line up on the same side opposed to parenting. This is a really interesting way to frame the issue, because it gets right to what's *really* being debated: can we intervene upon this causal relationship?
When people say something is 'natural' or 'biological', there's often the suggestion that it's immutable, driven by iron laws; when people say something is 'cultural' or 'socially constructed', there's often an insinuation that this is something we have a duty to change. The 'nature versus nurture' stuff is being used as a proxy for 'immutable versus alterable'. But as Caplan's analysis shows, and as Scott Alexander argues much more explicitly (https://slatestarcodex.com/2014/09/10/society-is-fixed-biology-is-mutable/), these are just two very different distinctions: very often we *can* quite easily intervene on biological variables, and very often cultural variables are too difficult to affect. (FWIW, I read Foucault as having a basically similar position to Alexander here, despite his bogeyman reputation among the type of people who use 'social construction' in scare quotes.)
I think that a stricter philosophical account of what goes wrong here might be: the assumption in 'nature versus nurture' or 'genes versus culture' debates is that you have two sets of causal relationships, biological and environmental, and you want to know which has a stronger causal effect on some variable of interest X (which might be income, education, openness to experience, weight, etc etc etc). But this is only a well-defined question if each type of causal relationship is unmediated by the other - if the casual graph looks something like:
B -> X <- E
But this is rarely the case. As your point about heretability shows, biological factors (the genes that encode 'five fingers') are typically mediated by environmental factors (the presence or absence of prenatal complications), and environmental factors (cultural ideals of attractiveness) are typically mediated by biological factors (a biologically-driven desire to be attractive to potential mates).* The casual graph instead looks something like this:
B1 -> E2 -> X <- B2 <- E1
Within this model, the question of 'which is the stronger causal influence, biology or environment?' no longer really makes sense, because both types of causal factor are mediated by the other. If you claim that biology is more important because B2 has a larger effect on X than E2, you have a problem in that B2 only has the value it does because of E1, and intervening on E1 would have a large effect on X through the intermediary of B2.
In this context, we can see that the *actual* interesting question is, 'which causal relationships can we intervene on?' What can we easily change? If we can easily change B2 directly, without worrying about E1, then it's reasonable to think of this as a biological problem; if we can only change B2 via changing E1, then it's more environmental. The question of the 'nature versus nurture' debate can thus be seen to be: is the best way to change the value of X to initiate radical cultural shifts in language and norms, or is it to protect the steady progress of science within a sturdy framework of social values? Phrased like this, it is obvious that these are not the only possible answers; it's deeply instructive that they're the answers that are implicitly at stake.
Indeed, the answer to this question is almost always context-dependent, depending on the value of X we're interested in. We probably can't intervene on biology, but might be able to intervene on the environment, when it comes to obesity; when it comes to attention, it's the opposite (Adderall works, yelling 'sit up straight and pay attention!' at children doesn't); when it comes to really complex variables like income and education, there will be some possible biological interventions, some possible environmental interventions, some implausible biological interventions, and some implausible environmental interventions. None of this is well-captured by 'weighing' genes against culture.
* Bernard Williams' 'Making Sense of Humanity' (the paper, not the book) is a more precise and general argument for why, in the context of human behaviour, we should expect biological factors to almost always be mediated by cultural factors. And the argument for the conclusion 'we should always expect cultural factors (or environmental factors more broadly) to be mediated by biology' is just the fact that we are biological creatures.
All Chinese have hailed IQ as the supreme indicator of human worth for almost 2,000 years and the results are in: to get an interview for a job with the national civil service, candidates need an IQ of at least 140.
Since the government only hires 27,000 officials each year, they further reduce the number of interviewees by requiring real evidence of a morally exemplary youth.
It may be sheer coincidence, but there are more prisoners, hungry children, drug addicts, poor people, suicides, executions, illiterate, homeless people in America than in China. And their kids graduate high school three years ahead of ours in STEM and can expect to live longer, happier lives.
My brother in law has dyslexia, and it is probably a genetic thing. One of his daughters, for example, has dyslexia as well. On the other hand, he is pretty smart, and despite his dyslexia, he managed to become an MD mastering a subject that requires a lot of reading.
The thing is that the human brain is extremely plastic. When one method becomes impossible, the brain can often figure out an alternative. For example, there was a patient who had a stroke and lost his ability to speak. He could, however, read written text aloud. He managed to converse by imagining what he was going to say typewritten across the forehead of the person he was speaking with and reading that aloud. This is obviously not the easiest way to converse, but he took advantage of the parts of his brain that were still working properly and their connections.
Some people may have a genetic problem doing one thing or another, but can take advantage of training and alternate methods to accomplish things. People have different learning styles and think using different types of metaphors - visual, linguistic, mechanistic, haptic - but they can be equally functional and equally expert. I'm sure that blind friend of mine back in college thought about derivatives in a way unlike mine, but she passed the same calculus course.
Who do you consider to be in the "genes are all that matter" crowd?
When environments are very similar, genes will account for almost all differences. When genes are very similar, environment will determine almost all differences. There is no fixed ratio.
Jesse Prinz's Beyond Human Nature is the best nurturist book I know, though it has serious flaws.
Naturism is heavily underrated writ large, but some nurturist critiques (especially of evo psych) are compelling.
I continue to think that Simon Blackburn's review of Pinker's The Blank State (https://swb24.user.srcf.net/reviews/Pinker.htm) is the best take on the whole 'nature versus nurture' framework - I think he pretty persuasively shows that the whole 'debate' is confused. Very much worth a read.
Caplan's book is a good example, because he has completely broken down the nature/nurture distinction: on his analysis, rather than genes being opposed to culture, *both* genes *and* culture line up on the same side opposed to parenting. This is a really interesting way to frame the issue, because it gets right to what's *really* being debated: can we intervene upon this causal relationship?
When people say something is 'natural' or 'biological', there's often the suggestion that it's immutable, driven by iron laws; when people say something is 'cultural' or 'socially constructed', there's often an insinuation that this is something we have a duty to change. The 'nature versus nurture' stuff is being used as a proxy for 'immutable versus alterable'. But as Caplan's analysis shows, and as Scott Alexander argues much more explicitly (https://slatestarcodex.com/2014/09/10/society-is-fixed-biology-is-mutable/), these are just two very different distinctions: very often we *can* quite easily intervene on biological variables, and very often cultural variables are too difficult to affect. (FWIW, I read Foucault as having a basically similar position to Alexander here, despite his bogeyman reputation among the type of people who use 'social construction' in scare quotes.)
I think that a stricter philosophical account of what goes wrong here might be: the assumption in 'nature versus nurture' or 'genes versus culture' debates is that you have two sets of causal relationships, biological and environmental, and you want to know which has a stronger causal effect on some variable of interest X (which might be income, education, openness to experience, weight, etc etc etc). But this is only a well-defined question if each type of causal relationship is unmediated by the other - if the casual graph looks something like:
B -> X <- E
But this is rarely the case. As your point about heretability shows, biological factors (the genes that encode 'five fingers') are typically mediated by environmental factors (the presence or absence of prenatal complications), and environmental factors (cultural ideals of attractiveness) are typically mediated by biological factors (a biologically-driven desire to be attractive to potential mates).* The casual graph instead looks something like this:
B1 -> E2 -> X <- B2 <- E1
Within this model, the question of 'which is the stronger causal influence, biology or environment?' no longer really makes sense, because both types of causal factor are mediated by the other. If you claim that biology is more important because B2 has a larger effect on X than E2, you have a problem in that B2 only has the value it does because of E1, and intervening on E1 would have a large effect on X through the intermediary of B2.
In this context, we can see that the *actual* interesting question is, 'which causal relationships can we intervene on?' What can we easily change? If we can easily change B2 directly, without worrying about E1, then it's reasonable to think of this as a biological problem; if we can only change B2 via changing E1, then it's more environmental. The question of the 'nature versus nurture' debate can thus be seen to be: is the best way to change the value of X to initiate radical cultural shifts in language and norms, or is it to protect the steady progress of science within a sturdy framework of social values? Phrased like this, it is obvious that these are not the only possible answers; it's deeply instructive that they're the answers that are implicitly at stake.
Indeed, the answer to this question is almost always context-dependent, depending on the value of X we're interested in. We probably can't intervene on biology, but might be able to intervene on the environment, when it comes to obesity; when it comes to attention, it's the opposite (Adderall works, yelling 'sit up straight and pay attention!' at children doesn't); when it comes to really complex variables like income and education, there will be some possible biological interventions, some possible environmental interventions, some implausible biological interventions, and some implausible environmental interventions. None of this is well-captured by 'weighing' genes against culture.
* Bernard Williams' 'Making Sense of Humanity' (the paper, not the book) is a more precise and general argument for why, in the context of human behaviour, we should expect biological factors to almost always be mediated by cultural factors. And the argument for the conclusion 'we should always expect cultural factors (or environmental factors more broadly) to be mediated by biology' is just the fact that we are biological creatures.
All Chinese have hailed IQ as the supreme indicator of human worth for almost 2,000 years and the results are in: to get an interview for a job with the national civil service, candidates need an IQ of at least 140.
Since the government only hires 27,000 officials each year, they further reduce the number of interviewees by requiring real evidence of a morally exemplary youth.
It may be sheer coincidence, but there are more prisoners, hungry children, drug addicts, poor people, suicides, executions, illiterate, homeless people in America than in China. And their kids graduate high school three years ahead of ours in STEM and can expect to live longer, happier lives.
My brother in law has dyslexia, and it is probably a genetic thing. One of his daughters, for example, has dyslexia as well. On the other hand, he is pretty smart, and despite his dyslexia, he managed to become an MD mastering a subject that requires a lot of reading.
The thing is that the human brain is extremely plastic. When one method becomes impossible, the brain can often figure out an alternative. For example, there was a patient who had a stroke and lost his ability to speak. He could, however, read written text aloud. He managed to converse by imagining what he was going to say typewritten across the forehead of the person he was speaking with and reading that aloud. This is obviously not the easiest way to converse, but he took advantage of the parts of his brain that were still working properly and their connections.
Some people may have a genetic problem doing one thing or another, but can take advantage of training and alternate methods to accomplish things. People have different learning styles and think using different types of metaphors - visual, linguistic, mechanistic, haptic - but they can be equally functional and equally expert. I'm sure that blind friend of mine back in college thought about derivatives in a way unlike mine, but she passed the same calculus course.
Danish twin study is 1870-1900*, not 1990.
If comparing heritability estimates, the time period must overlap with Ruth et al.
I'd expect the heritability of longevity to increase in the 20th century due to fewer deaths caused by contagious diseases, accidents, etc.