Nature, Nurture, and the Height of Racism

Or why biological differences between difference "races" are not necessarily anything to do with "race"

This post is not really about human height or race or nature versus nurture (though it concerns all these subjects) it is about the way in which we are so easily led astray when we think about such matters.

People from (say) the UK who go to (say) Japan (I haven’t as it happens) tend to note that the average Japanese person is shorter than the average person back home. This is certainly a recurring theme in the (sometimes borderline racist) film Lost in Translation[1] – though the visitors in that case were, of course, American.

What is the explanation for this difference? It is tempting to jump to the conclusion (as the Daily Telegraph’s questionable Short people have 'shortage' of genes - from where I stole the picture of the three women above - appears to) that it is all down to genes.

I suppose the reasoning goes something like this:

1) British people are taller (on average) than Japanese people (probably true).

2) Height is highly heritable (certainly true).

3) British people have different genes to Japanese people (sort of true).

ergo

The difference in the average height of British people and Japanese people is explained by their differing genetic make-ups (QI-style klaxon should go off).

Counter-intuitively (at least if your intuitions are the same as mine were before I knew anything about genetics) this reasoning is entirely fallacious[2]. NB: This is not to say the conclusion itself is necessarily wrong. I do not actually know how much, if any, of the average difference in height between British people and Japanese people is explained by genes and I am not sure anybody really does for certain. Moreover, I do not think this is a particularly interesting topic. The reason why the reasoning presented above is wrong is, however, rather interesting.

Let us take each of the premises in turn:

1) British people are taller (on average) than Japanese people

According to Society at a Glance 2009: OECD Social Indicators - OECD 2009, the average height of Japanese men was 1.72m (when measured in 2005) and that of UK men 1.77m (when measured in 2006). So there is an average difference, but only one of about 5cm.

2) Height is highly heritable

A few years ago there was a comedy film (which I confess I’ve never actually seen) starring Arnold Schwarzenegger and Danny DeVito masquerading as (presumably) dizygotic (non-identical) twins:

It is well established that tall parents tend to have tall children and small parents tend to have small children. Of course, we can all think of exceptions to this “rule” and if AS and DD really were twins they would constitute such an exception. In real life, we know that AS and DD are not really twins and I rather expect that AS had taller parents and DD had shorter ones. But I think we can safely assume that, even if they had been brought up in the same household and given the same diet and activities throughout life, AS would have still turned out much taller than DD. To put this into scientific terms: the variation[3] in human height across populations really is largely explained by genetics – approximately 80% of the variation according to Scientific American.

3) British people have different genes to Japanese people

What probably strikes most British people first about Japanese people is their epicanthic eye folds – though this trait is by no means exclusively found among Japanese and other East Asian people. The trait is also sometimes encountered in “white” people in places like Poland and Finland and in “black” people and in parts of Africa in places such as Namibia. The trait is nevertheless, even if not a necessary or sufficient condition of “Eastasianess”, clearly genetic. Japanese people (unlike Brits) also tend to be lactose intolerant. This is another clearly genetic trait - albeit a less visible one and one that is also found (somewhat surprisingly) in my very Teutonic looking German nephew and, as it happens, in most of the world’s population[4]. Height in humans is, to the extent it is determined by genes, determined by lots of different genes working together in complicated ways and it is entirely possible that “tallness genes” are less common among Japanese people[5]. But the fact that Japanese people have characteristic features or eschew the consumption of lactose-rich comestibles gives us no particular reason to jump to any conclusions on the presence or absence of other genes in that population[6].

But surely, the man on the Clapham Omnibus insists, consistent differences – with respect to highly heritable characteristics (like height) – between distinct populations must be largely due to nature rather than nurture?

As the song goes, “it ain’t necessarily so” …… and here’s an explanation of why:

Imagine that the aforementioned Arnold Schwarzenegger and Danny DeVito had both really been blessed with twin brothers - monozygotic (identical) twins. Let us call them Colin Schwarzenegger and Basil DeVito. Let us further imagine that the two sets of twins were cruelly separated at birth and each paired off with one of the other set of twins: Arnold and Basil banished at birth to the otherwise uninhabited “Short Island” (an Island where there were very meagre supplies of food); and the (more fortunate) Colin and Danny to “Long Island (where food was plentiful).

On Short Island, A and B both reach adulthood but their growth is stunted:

The luckier C and D on Long Island achieve their full potential (at least from a growth point of view):

(I don’t know how they came by their suits.)

So here we have a case where there is a significant average difference between the (admittedly small) populations of the two islands and where the difference relates to a highly heritable characteristic (to wit height). The variation in height (the difference between A and B on SI and the difference between C and D on LI) is (assuming they shared their rations on SI fairly) entirely due to genetics. Nonetheless, the difference between the two populations, in this thought-experiment, is entirely explained by the differences in the two environments.

This example is, of course, rather contrived. In real life, it is far more difficult to establish whether differences within and between populations have largely (or entirely) genetic or environmental bases. But what this example conclusively demonstrates is that argument presented at the start of this post is a non sequitur. Just because there are significant differences (with respect to highly heritable traits) between nations or races (or any other groups of individuals we care to demarcate) does not entitle us to conclude that those difference are explained by nature rather than nurture.

In other words, the mere fact that differences in height within the UK and within Japan are largely explained by genetics does not - in and of itself - entitle us to conclude that the difference between the UK and Japan explained by genetics. Armed only with that information, we cannot decide whether the difference between the two populations is largely (or entirely) explained by (say) diet rather than by genes. Neither conclusion is ruled out or established by the fact that height is highly heritable.

So next time you hear someone observing that “Jews are clever with money” or “Black people make good runners and have a good sense of rhythm” or “Asian people are highly intelligent” or “Hungarians are good at chess” or whatever, please bear in mind that, even if such claims are statistically true and even if being good at handling money, running, playing the drums, and playing chess are highly heritable, it doesn’t necessarily follow that Jewish, Black, Asian, or Hungarian genes have anything much to do with the observations made.

It should, perhaps, also be added that (let’s play safe here and take the most innocuous example) even if there are genes for being good at chess and these really are more common amongst Hungarians and this “fact” really does explain Hungary’s historical prowess in this field, the implications for social policy are very limited. After all, we know that men are better at running than women and that this fact is explained by biology (men are, after all, taller than women); but if you had a requirement for a fast runner and Paula Radcliffe and I applied for the job, I rather think it would be a mistake to be guided in your choice of candidate by your knowledge of general biology and gender.

In short, neither reason nor science do (or could) lend any support to racism (or sexism).

1. A film – like the even more questionable Breakfast at Tiffany’s - I confess I rather enjoyed, despite my discomfort at the casual (though unconscious and unintentional) racism.
2. Of course if the trait were 100% heritable (like blood grouping) such an inference would be valid.
3. I wrote here about the difference between explaining things like height by genetics and explaining the variation in things like height by genetics.
4. A story for another day.
5. The implication of the article I pinched my picture from.
6. I explore the theme of race and genetic essentialism here.

Why Michael Gove's department is confused about genes and education; and why you probably are too.

In the Guardian on Saturday October 12 it was reported that Michael Gove's special adviser Dominic Cummings had "provoked outrage" by claiming that "up to seventy percent of a child's performance is related to his or her genes".

Now it seems that Mr Cummings has been mis-quoted here. I happen know this because he told me himself in a tweet. His twitter name is @odysseanproject – which I suppose will amuse fans of Diary of a Nobody. Mr Pooter’s favourite joke about his friends Gowing and Cummings was that Gowing was always coming and Cummings was always going.

But I digress.

What the Guardian ought to have said and (it seems) Dominic Cummings did say is that "up to seventy percent of the variation in children's performances is related to their genes".

So why is that different from saying "up to seventy percent of a child's performance is related to his or her genes"? To see why, we need only consider the following simple thought experiment:

Imagine you adopted two randomly chosen children born one the same day (Mary and Jane perhaps) and gave them exactly the same upbringing, environment, life experiences, and education. (Of course that would be impossible in practice, but this is only a thought experiment.) Now imagine that we tested them both (several times perhaps to make sure one of them was not having an off day) at eighteen years old and Mary got straight Bs and Jane got straight Cs.

The variation in the results of the two individuals must, I hope you see, be entirely due to their respective genetic makeups.

Now let us repeat the thought experiment but provide much better education. This time (we could imagine) Mary gets straight As and Jane gets straight Bs. The variation in the results of the two individuals must still be one hundred percent due to their respective genetic makeups. The improvement in results is, however, entirely due to the change in environment - specifically the improvement in education.

This observation illustrates why Dominic Cummings's statement (as mis-reported) is drivel. The seventy percent figure relates to the explanation for the variation in a population not to the performance of an individual.

Asking about the relative contributions of genetics and environment to a particular child’s performance is a bit like asking what whether the height or the length of a rectangle contributes most to its area. Such a question makes no sense.

Asking about the relative contributions of genetics and environment to variation, on the other hand, makes perfect sense.

Some things in a human population may be vary a lot – like personal income. Other things in a human population may vary much less – like height – you do not find people who are two million meters tall for example.

The degree of variation in a population can actually be quantified. (This is quite complicated, and there are different ways of doing it, but let us just stick with the basic idea.) Once we have quantified the amount of variation, we can talk about what factors contribute most to that variation.

If, in the case of school children and academic performance, we took away one of the contributions to variation (which we could do in theory) by breeding a cohort of school kids who were all genetic clones (which would take away the variation due to genetics) or by giving a cohort of school kids exactly the same education (which would take away the variation due to quality of education); in either case, the amount of variation in the population would be reduced. It would obviously be reduced more if you took away whatever was making the biggest contribution.

If we pretend for the moment, and for the sake of simplicity, that education and genes are the only factors (of course there are many others such as social class, but let us keep things simple) what may seem slightly paradoxical is that if we gave all children exactly the same education, though this would reduce the variation in the population, it would increase the relative contribution of genetic factors - it must do so because all variation in a population receiving exactly the same education must be down to the genes.

Of course, as I expect almost everyone agrees (regardless of their politics) the variation in academic achievement (and many other attributes) of the population depends on a complex mixture of factors. Teasing out the relative contributions of the various factors is far more tricky than you might think. Even if we take something like height - which is far easier to measure objectively than academic ability and is undisputedly highly heritable (tall parents tend to have tall kids and vice versa) - it is still far from clear to what extent the variation in human height around the world is down to genes or environment.

I have no idea what the correct figure is for the genetic contribution to the variation in academic achievement in the population at large, but (though I am very much on the political left) it wouldn't surprise me at all to learn that the true figure is even higher than seventy percent.

But, given the fact that nobody knows the facts for sure, people at either end of the political spectrum are wont to provide ideologically-driven rather than data-driven answers to the empirical question: How much is nature and how much is nurture? Hence the irate tone of much of the discussion on this topic in the media this week.

The left's commitment to egalitarian principles lead them to conclude that it must be mostly due to nurture. Only if we believe that, they suppose, can we imagine a future where social inequities are put right through progressive social intervention.

The right's commitment to in-egalitarian principles lead them to conclude that it must be mostly due to nature. Only if we believe that, they suppose, can we justify the claim that doing anything to improve the lot of the hoi polloi is a waste of time.

So why do I claim that both sides get the whole thing rather back to front?

Let us conduct another couple of thought experiments:

First let us first suppose that we have the most extreme case possible of the frequently encountered left-wing belief about the way the world is. Everyone in our imaginary society is a genetic clone with an exactly equal genetic endowment of academic potential and any differences in ultimate achievement will be entirely due to how we nurture the individuals concerned. How would we then structure our education system? We should have to choose individuals completely arbitrarily from the pool and train some of them up to be clever enough to be surgeons or rocket scientists or whatever; and - at the other end - some of them to be just clever enough to tie their own shoe-laces so that they could perform jobs requiring very little intelligence - like the job of Education Secretary I suppose.

But isn't this more or less what right-wing education policy has always been (and what the likes of Michael Gove and Dominic Cummings seem to want to go fully back to): a system where people are picked arbitrarily from the pool on the basis of social class (rather than innate ability) and given the training they require to fulfil their allotted stations in life?

Now, instead of a society of genetic clones, let us imagine a society where everyone is born with different potentials. No matter how well I had been nurtured, I could never have become a Premiere League football player; and the likes of Michael Gove could, no matter how well he had been nurtured, never have understood averages or become a professor of thermodynamics.

...a bit like the world Dominic Cummings and other right-wingers (probably largely correctly) believe we do inhabit.

In this world, it no longer makes sense to choose people arbitrarily from the pool and nurture (only) them. The only policy that makes sense is to nurture everybody so that each person achieves the best he or she is capable of and those who come out on top represent those who started out with the best genes rather than those who were fortunate enough to be given an education.

...rather like the sort of education system left-wingers tend to argue for in fact.

Okay, I've over-simplified here and rather caricatured the various political positions, but I hope I have also successfully made a serious point: the thinking about nature and nurture, on both left and right, is often terribly confused.





A version of this post was included in the @pod_delusion podcast of 2013-10-17.