Japan’s population will bounce back - sort of

From Wikipedia

Japan's TFR (Total Fertility Rate) is around 1.34. This is the average number of children a Japanese family will have in contemporary Japan. The TFR which maintains a steady population level is 2.1 (some fraction of children do not reproduce through death, ill-luck or disinclination).

People conclude that the Japanese as a country-community are doomed. Since European TFRs are similar, averaging around 1.6, this repugnant conclusion seems quite generalisable.

But people who write sensational stories in the media about this pay only lip service to evolutionary theory, they don't operationalise it. This bland, average TFR hides subpopulations, some of which don't reproduce at all, but others of which are quite prolific in family size.

Since there is parental genetic influence on the size of family [1] we can treat this fecundity-variance as setting up a process of genetic truncation selection. The structure and incentives of Japanese society (a proxy for almost all advanced countries) poses enormous Darwinian selection pressure against those individuals with genotypes which encourage them to fail to reproduce adequately.

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A simple Fermi estimate (a back of the envelope calculation) allows us to predict the result of this massive selection pressure on the Japanese population, in generation time steps.

Simplifying the numbers in [2] below, divide Japanese families into four categories with the following endogenous TFRs:

 - category zero is 25% of the population with TFR zero

 - category one is 33% of the population with TFR one

 - category two is 33% of the population with TFR two

 - category three is 9% of the population with TFR three.

So this is the population structure at generation 0. 

Assume for ease of calculation that the population of Japan is 123 million. We divide this into three generational age cohorts: 0-25, 25-50,50-75 and assume each cohort is equally numerous at 41 million people.

Over one generation the upper cohort dies (losing 41 million people) and the middle cohort reproduces to replace them (or not).

To make things more intuitive we will replace the percentages with 100 notional families representing those individuals who reproduce, namely the 41 million strong middle cohort. Call them 40 million to make the sums easier. So each 'family' represents 400,000 people. 

What happens to the population as the generations roll over?

Generation 1: 2025 => 2050

We started with 123 million. The elderly cohort dies leaving 82 million. And now the logic of extreme selection kicks in: 

 - category 0, 25 families, are culled from the gene pool and vanish 

 - the 33 families of category 1 are replaced by 16

 - the category two families simply replace themselves, remaining 33

 - the category three families increase their number by 50% to fourteen.

Total number of families is 16 + 33 + 14 = 63. The newborn population is 63 * 400,000 = 25 million. The new population is 82 million + 25 million =  107 million. This is consistent as it happens with the chart at the head of this post.

(Note: the resulting TFR here is 25/20.5 = 1.2 so our back of the envelope calculation is a slight under-estimate).

Quite a drop from 125 million.

What happens next? Those alleles which support a propensity to have children have increased in frequency, but we know the heritability of this trait is not high. So as generation 1 transitions to generation 2 in 2075, we will still see some families having zero offspring (or never forming a family unit at all) while the percentage of those families favouring more offspring will increase.

The modelling would be complex and noisy, but the direction of travel is clear. Darwinian selection is doing its work and a new population being selected for, composed of those families interested in having children despite all the many modern distractions. 

Inexorably, the population of individuals who genetically underpin category three will rise exponentially and will eventually dominate in the population, which will itself substantially rise in numbers if it can manage to sustain itself.

There is an interesting implication, which escapes no-one who thinks about this in an informed way, that any other genetically-informed traits which co-vary with fertility-promoting alleles will also be selected for. I admire many aspects of Japanese culture but my ignorance of the details of Japanese society is pretty much total. Still, someone much more informed than me should take a look.

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[1] Heritability of family size (from Bard)

Here are some examples of heritability estimates for family size in different countries:

Denmark: 15-20%

United States: 20-30%

Australia: 25-30%

Netherlands: 30-40%

Japan: 20%

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[2] From Bard - family sizes in Japan: 

Here are some specific percentages you might find helpful, based on data from 2020:

Percentage of women aged 45-49 with no children: 22.7%

Percentage of women aged 45-49 with one child: 32.5%

Percentage of women aged 45-49 with two children: 34.2%

Percentage of women aged 45-49 with three or more children: 10.6%

When well-intentioned people write bad things

It's not that Matt Ridley hasn't got form. There's a veneer of political correctness which seems to stick to public-intellectual science-writers; they persist in writing cosy, comforting pieces they must know to be misleading, even untrue.

Today, Ridley has an op-ed piece in The Times. "Gene editing isn’t a slippery slope to eugenics", trying to rehabilitate the notion of eugenics.  This is opportune given the dysgenic features of advanced Western countries (relaxed selection leading to mutational load, & the idiocracy stuff), combined with the ameliorating possibilities of genetic engineering.

Ridley starts with the correct statement that eugenics is bad when coercive. State-controlled reproduction is oppressive whether it's China's one-child policy, India's compulsory sterilization or - that old favourite - the disreputable practices of Nazi Germany.

So few problems with his first point:

"First, the essence of eugenics was compulsion: it was the state deciding who should be allowed to breed, or to survive, for the supposed good of the race. As long as we prevent coercion, we will not have eugenics. Our politics would have to change far more drastically than our science."

His second point is more dubious - reassuring cant, some might call it. Artificial insemination with the eggs or sperm of strangers is not what most couples want - they made their own eugenic selection when they chose their partner.

"The second reason we need not fear a return of eugenics is that we now know from 40 years of experience that without coercion there is little or no demand for genetic enhancement. People generally don’t want paragon babies; they want healthy ones that are like them. At the time test-tube babies were first conceived in the 1970s, many people feared in-vitro fertilisation would lead to people buying sperm and eggs off celebrities, geniuses, models and athletes. In fact, the demand for such things is negligible; people wanted to use the new technology to cure infertility — to have their own babies, not other people’s. It is a persistent misconception shared among clever people to assume that everybody wants clever children."

But what if their own child-to-be could be tweaked a little? Or there could be a little bit of selection amongst all their possible children? This is already pretty popular for genetic disease screening; and rightly so.

And then we descend to the plain wrong.

"The more recent discovery that traits such as intelligence are caused by the complicated interaction of multiple genes of small effect means that it is anyway going to be virtually impossible to decide what genetic recipe to recommend to somebody who wants a clever child, or a good-looking one, or an athletic one. By contrast, the genetic changes that cause terrible afflictions such as Huntingdon’s disease or cystic fibrosis are singular and obvious. Selecting embryos that lack such traits, or editing the genes of people so that they are born without carrying such traits, will always be much easier than selecting genetic combinations that might, in the right circumstances and with the right upbringing, lead to slightly higher IQ. Cure will always be easier than enhancement."

We know that embryo selection on as few as ten fertilised eggs could span an IQ gap of ~11 IQ points. That would boost Caucasian populations to the level of the Ashkenazim in one generation. And not a CRISPR in sight.

There is little reason to believe that genetic engineering of many hundreds of SNPs wouldn't be possible within two generations, resulting in significant trait alterations on any reasonably-heritable trait - which is most of them.

We're talking height, health, athletic ability, musicality, personality .. and of course IQ here.

So, Matt, it's not going to be so hard and, trust me, they'll all be jumping at it once it's safe and cheap.

And you must know this. So what's with the 'reassuring' lies?

Diary: foot problem + Game of Thrones + AlphaGo + genetics

I vaguely recall jamming my foot against the side of the bed while hoovering last week. By Easter Sunday the entire right foot was red, the skin taut and swollen over the toe joint and I was limping around in socks. The last few days have seen a slow improvement but I think it may be the weekend before I can claim to be back to normal. Some observations.

1. I haven't taken any pain medication, believing that pain is a signal which I do well to heed and analgesics probably mess up self-healing. I recognise I may be in a minority on this.


2. The body's response to damage seems to affect many aspects of its functioning, not just the topical region. I feel a bit tired and - strangely - a bit more relaxed, like I'm let off worrying about stuff. Interesting.


3. Doctor Google was reassuring. The alternative suggestion of gout was excluded - no causal pathway from over-indulgence in Easter eggs.

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A Game of Thrones (book vol 1) is highly addictive, once you've printed off the family trees of the various noble houses. It reminds me how natural the ties of family, personal loyalty and honour are, and how alien the cool, depersonalised, transactional styles of modern urban capitalism. No wonder American politicians and business people engaged with negotiators from traditional societies talk past each other in mutual incomprehension.

What would the noble protagonists of GoT make of "The Martian", which we saw on DVD Saturday evening?

The hero is some kind of insolent, wise-cracking, artisan-monkey who refuses to die quietly on Mars as he should. His liege-lord commander shows weakness by beating herself up over leaving him (she did her duty: so problem?).

The world actually cares about this minion, and the powers-that-be indulge their idiotic sentimentality. Could never happen.

Thank the Gods it's only far-fetched speculative fiction.

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I thought this was a good article about AlphaGo - assessing its significance now the dust has settled a bit.

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This from Professor Greely, Director at the Center for Law and the Biosciences, Stanford University, as set out in his book, 'The End of Sex and the Future of Human Reproduction'.

“In 20 to 40 years, when a couple wants a baby, he’ll provide sperm and she’ll provide a punch of skin,” Prof Greenly told The Times.

"He said the female skin sample will be used to create stem cells, which can in turn be used to create eggs.

"These eggs can then be fertilised with the sperm cells, resulting in a selection of embryos.

"Prof Greenly predicts these embryos will be studied for any signs of malady.

“The prospective parents will be told, ‘These five have really serious diseases, you don’t want them’.

"Of the other 95, they will be given the pluses and minuses,” he said.

"He said that after weighing up the prospective advantages and disadvantages of the healthier embryos, the parents will choose one to be implanted into the woman, which will become their child.

“Parents will get the embryos grouped by categories,” Prof Greenly said.

“One category will be very severe, untreatable, nasty diseases. This will affect one to two per cent of embryos.

“Another category will be other diseases.

“The third is cosmetics: hair, eyes, shape, whether the hair goes white early. We don’t know much about this yet, but we will.

“A fourth category is behavioural. I think here information will be limited. We won’t be able to say, ‘This child is in the top one per cent of intelligence’. We probably will be able to say, ‘This child has a 60 per cent chance of being in the top half’.”

He's being judiciously careful here. In 20 years time we'll be able to read off from the genome both IQ and personality type more accurately than current psychometric testing can.

Choose the best of your virtual children

I wrote critically of Nick Bostrom in my review of his "Superintelligence" book. But when he's not writing in a philosophical straightjacket, his intelligence and creativity produce rather better results, as here with Carl Shulman.

Suppose you have nine brothers/sisters. Your nine siblings will, of course vary in height, weight ... and intelligence. We know how to think about the relationship between the IQ of parents and their offspring (Steve Hsu explains here).

• We take the average of the parents' IQ, and that is the mean IQ of their children.


• The children do not of course have identical IQs, they're not clones; instead they populate the usual Gaussian distribution with standard deviation in the 7-11 IQ point range (rather than the usual population IQ SD of 15). The authors were conservative and used 7.5 in their simulation below.

So Carl and Nick have this table in their paper, from which you can see that the maximum IQ gap within ten children (dimmest to smartest) might be as much as 23 IQ points. Yes, I find that surprising too.

The table is based on a large scale simulation (10 million couples) and what I take it to be saying is this: if you use ten embryos and decide to implant the smartest, then you'll get an average 11.5 IQ point gain over just selecting a random embryo with no pre-screening for intelligence at all.

Is that important? It's the difference between a clerical and a professional job.

If you come from a large family, consider your siblings and consider whether any of this makes any sense.

We already do embryo selection for single-mutation diseases. A fertilised egg (in vitro) is allowed to divide until you have, say, an eight-cell clump - at this stage there is no functional differentiation. One cell is then extracted and its genome sequenced looking for the faulty gene. If the genome is fine, the seven remaining cells are implanted and the embryo grows to term with no ill effects; otherwise, discard and repeat. (It is more complex than this).

For IQ-based embryo selection to catch on we need a predictive model which can take a sequenced genome and predict with tight accuracy the resulting IQ (assuming decent nutrition, no abuse etc). We can't do this now as the relevant genes haven't yet been identified. But that should change within five to ten years. And we need to get the cost right down: doing 10 whole-genome sequences could be pricey.

Apart from the hassle of IVF and any legalistic hurdles, the way would then be open. What might be the consequences? Carl and Nick have a table - click on it to make it bigger.

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Just a note about IES on the right-hand side.

"The effectiveness of embryo selection would be vastly increased if multiple generations of selection could be compressed into less than a human maturation period. This could be enabled by advances in an important complementary technology: the derivation of viable sperm and eggs from human embryonic stem cells. Such stem cell derived gametes would enable iterated embryo selection (henceforth, IES):

1. Genotype and select a number of embryos that are higher in desired genetic characteristics;

2. Extract stem cells from those embryos and convert them to sperm and ova, maturing within 6 months or less;

3. Cross the new sperm and ova to produce embryos;

4. Repeat until large genetic changes have been accumulated."
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"Using IES could deliver much more extreme results, and the fixed costs of using IES to produce enhanced embryos could be spread across large numbers of enhanced children. On the other hand, IES would compromise the typical genetic relationship between parents and children. To avoid negative effects of inbreeding, IES would require either a large starting supply of donors, or the expenditure of substantial selective power to reduce harmful recessive alleles. These factors would tend to push towards IES offspring being less genetically related to their parents (though more related to one another), and could reduce the appeal of IES."

All this and we haven't even mentioned genetic engineering, or CRISPR-Cas9.

I blogged that Toby Young had a piece about this back in September last year.