August 28, 2013
How Parents Will Guarantee They'll Get Grandchildren

Prospective parents will use offspring genetic engineering to give their children strong instinctive desires to have their own kids. They'll do this to guarantee that their kids make grandchildren.

The result? Human population explosion.

I do not see how we can avoid human population explosion.

Share |      Randall Parker, 2013 August 28 10:07 PM 

Vektor said at August 29, 2013 6:34 AM:

I doubt it. The institution of marriage itself is seriously broken and becoming more marginalized each passing year. Countries even try to pay couples to have children and/or penalize them with 'bachelor taxes', and it still does not reversing falling birth rates. Individualism in young people has never been stronger - this does not lend itself towards pair-bonding. The inevitable economic collapse will not promote family formation either.

However, there is an interesting aspect to this theory...

If science can definitely identify a genetic basis for homosexuality vs. heterosexuality, and parents can act on this information based on personal preferences, that opens up a huge can of worms. I can foresee a massive legal/ethical battle to prevent this option from becoming legal. Bottom line: if parents want grandchildren, having a homosexual child really doesn't facilitate that.

jp straley said at August 29, 2013 7:27 AM:

A slow reduction in population is not a bad idea at all for western countries. (For all of them, but I'm from the West.) However, the problem will be policing trans-national companies from importing large numbers of third-worlders for cheap labor. These persons will take root and stay, and then you have a reproductive competition that can only end with one tragic result.

You are correct about homosexuals. In terms of genetic continuity (or family continuity if you want to phrase it that way), it is the death of a child. That's a key reason why families get so worked up about adult homosexuals wanting to seduce their young adults.

Vektor, since I am in a very happy marriage, and know many others, my experience in quite in opposition to your scanario. Maybe you are hanging around with the wrong people!

Ronald Brak said at August 29, 2013 8:23 AM:

I really don't think there is any desire there to genetically engineer. People do have sex drives. Sex, both real and simulated, is a multi billion dollar industy. But people don't actually seem to have a genetic desire to have children. I think this because as far as I am aware no one makes money from simulating the experience of having children. For example, I'm not aware of any people of diminuative stature being paid to come around to people's houses and smear dirty fingerprints on monitors, constantly demand attention, have temper tantrums, and urinate while sleeping in bed. I suppose that pets might come the closest to paying money to simulate having children, but I think pets are popular precisly because they have a number of advantages over children. And if you don't believe that this is the case, try making your five year old child sleep in the back yard and see how long it takes for you to suffer social and legal complications.

destructure said at August 29, 2013 12:45 PM:


You assume that since you have a sex drive but no desire for procreation that others are the same. You imply that having children is merely a consequence of the sex drive only. IVF and adoption prove otherwise. If procreation and intercourse were mutually exclusive and I had to choose between the two, I'd choose procreation and never think twice.

Ronald Brak said at August 29, 2013 4:37 PM:

Destructure, hundreds of millions of people have a desire to use the internet but I don't think that's genetic. So I don't think internet use desire is something that can be genetically modified in any direct way. And I don't think there are genes that can be altered to directly influence people's desire to have children. Note that I'm not saying it isn't possible to make a difference in procreation rates through genetic engineering. For example, genetically engineering people so they have wide hips might make childbirth easier and more pleasant for women and so have an effect on the number of children they have, but while pelvic girdle width is something we can probably directly affect through fiddling with genes a general desire to have children probably isn't.

Acksiom said at August 29, 2013 6:05 PM:

>I do not see how we can avoid human population explosion.

Now you're just trolling me.

For the fourth time, I'm pointing out to you this solid and serious counterpoint:

>The only way I can see to prevent it: government-mandated genetic engineering of offspring to reduce the next generation's desire to have kids.

What about the coming RISUG/Vasalgel revolution in male birth control? They're expecting FDA approval for market release in the usa by 2015. I'm confident that a 99+% reversible MBC injection with a 10-year lifespan will be more than popular enough to throw off all their predictions. Did they mention that at all?

Randall Parker said at August 29, 2013 8:54 PM:


Women want babies far more than men. Some women want babies far more than others. There are lots of genetically caused correlations with the likelihood of making babies. Of course the desire for babies has a large genetic component.


You flatter yourself. I was responding to discussions elsewhere when I decided to write this post. One of those discussions was about the desire for grandchildren.

Your point about male birth control: it is not responsive to the argument I'm making: people have an instinctive desire for babies. This is very obvious. Therefore I haven't responded to your argument or even thought about it much. But since you seem to want a response here is one:

Lots of people go off birth control in order to make babies. Why? Because they want babies. Birth control does not prevent intentional baby making. Birth control has increased the amount of sex for people who want sex but not babies. Lots of married people live together for decades without making babies and others have just exactly the number of kids they want. They use IUDs, diaphragms, birth control pills, condoms, spermicidal foam, and other methods. Another form of birth control won't matter much for those who actually want to make babies.

destructure said at August 30, 2013 1:51 PM:


That's shoddy and disjointed reasoning. First, it's a false analogy. There's no known connection between internet usage and desire for procreation. Therefore, whether there's a genetic basis for one has nothing to do with the other. And, second, studies suggest there actually is a statistically significant correlation between a particular gene and excessive internet usage.

sycamore said at August 30, 2013 4:21 PM:

Brak you are wholly mistaken. Virtually every single human trait that has been studied has a narrow-sense heritability around 0.3-0.8+.

For facial appearance it's about 0.98 (consider identical twins raised apart).

Most often it is around 0.5.

You can construct a silly sort of trait for which the heritability will be near-zero, such as being born on a prime-number date. But that's cheating.

Literally just about all 'normal' traits have high heritability (>0.3) -- and I would say about a few hundred of them have been thus examined -- so 'internet use drive' and procreation drive are well over 95% likely to conform to pattern. Bet you a thousand bucks.

By the way I am assuming you are considering these traits quantitatively: degree of procreation drive, degree of internet use -- as opposed to the desire to use the internet zero times vs the desire to use it one or more times. If not, you are still gonna be wrong, but the discussion would be more complex.

> Another form of birth control won't matter much for those who actually want to make babies.

True, yet not all babies are (fully-)intended. Therefore I think it may have some short-term or small-scale relevance in the population, insofar it is not identical to the other forms of prophylaxis.

But I think your point is that humans are, and have been, undergoing extremely powerful positive selection for procreation drive. This is obviously true, and the new kind of prophylaxis will have modest-to-zero impact on this process. Zooming out to a large temporal scale such as 1750-2250, the impact will doubtless be entirely negligible. Indeed, it will most likely be nearly negligible over just 2013-2113.

Virtually Nonymous said at August 31, 2013 12:59 AM:

We are not going to have a human population explosion because of the limits to growth. The earth can only support so many people, and that number is going to decrease as energy and resource scarcity increases. The limit for the amount of people it can comfortably support is substantially lower.

The only thing I can foresee allowing human population to continue to "expand" is a mass die-off/war/catastrophe.

Ronald Brak said at August 31, 2013 1:37 AM:

My great great aunt had 23 children. My grandmother had seven. My mother had three, and my sister has one. If my great great aunt had genes that made her desire children, why is the current generation of female Braks so happy with three, two, one, or zero children? If my family lacked the genes that create a desire for children and only had huge numbers of chidren in the past because of other factors, then other families that did have these genes should have consistantly had members that had huge numbers of children all through the demographic transition. If these familial lines of super breeders exist they should be easy to detect. Has anyone dectected them? Or is their distribution more like what would be expected if there wasn't a strong genetic desire to have children that was independant from other factors?

Brett said at August 31, 2013 1:49 AM:

Isn't the reductio ad absurdum of Randall's argument that we will make clones of ourselves?

Randall Parker said at August 31, 2013 7:06 PM:


It is wearisome to have to demonstrate the obvious.

Fertility boosting gene found in Hutterites. 40 genetic regions influence fertility in Hutterite men. Among Quebecois natural selection operated to lower the age of puberty and fertility. From the PNAS paper “Our study supports the idea that humans are still evolving. It also demonstrates that microevolution is detectable over just a few generations.” I wrote about that report. Multiple genetic variants lower the age of puberty and surely they are all being selected for now. Other attributes that raise fertility are being selected for including religiosity. Shorter and heavier people have higher fertility. More on overweight being selected for. Higher intelligence being selected against.

What is being selected for: attributes that raise fertility. Since some groups have higher fertility for genetic reasons they'll be larger fractions of future generations and those future generations will have higher fertility. Some of those attributes are instincts.

I spent about an hour coming up with links. This was not an exhaustive search.

Great great aunts that had 23 children: now the selective pressures are working against what caused that big drop in fertility. Those selective pressures did not exist a couple of hundred years ago. They exist today. Since there are lots of alleles that influence fertility those selective pressures have much to operate on.

Ronald Brak said at August 31, 2013 8:31 PM:

Randall, we seem to have got our wires crossed. I am not saying that alleles that result in increased fertility are not being selected for. Of course they are. What I am saying is something very different and that is I doubt that humans have a specific desire for children that can be directly influenced by genetic engineering.

Chris said at August 31, 2013 9:07 PM:

Ronald Brak, I'm having trouble parsing what you're even saying. Alleles that result in increased fertility being selected for seems perfectly sufficient to result in what Randall fears. How is it not? Like people have exhaustively pointed out, all sorts of personality traits every bit as subtle as those for desire to have children have been shown to be heritable. There is no reason that I can see to suspect that this one aspect of personality is any different. Why do you think it is?

Randall Parker said at August 31, 2013 10:15 PM:

The desire for kids seems to go down in women by 25% for every 15 IQ point increase. I interpret that as the more powerful prefrontal cortex asserting its interests above that of the rest the brain. A dumber prefrontal cortex gives into the instincts from deeper parts of the brain.

Engineer-Poet said at September 1, 2013 5:29 AM:

So the solution is what?  Genetically engineer the Y chromosome so that it has most of the promoters for the genes which up-regulate intelligence?  Sounds Kzin.

Ronald Brak said at September 1, 2013 7:48 AM:

Randall, I think a woman who has to forgo a $100,000 dollar a year career to have children is less likely to have them than a woman who has to forgo a $20,000 a year job. I don't think a successful struggle against instincts is necessary to explain why smarter/more educated women have lower than average fertility.

Red said at September 1, 2013 8:37 AM:

In any civilization stupid people will out produce the smart until the civilization collapses and starves it's way back to normal. The civilizations that avoid this are the ones that periodically kill of their poor though war, famine, or hash treatment of stupid people.

The human brain was bigger at the end of the last glacial period than it is now. We've been getting dumber for 10,000 years. If you want to reverse that trend then get ready to kill a lot of stupid people.

Engineer-Poet said at September 1, 2013 10:01 AM:

You don't have to kill them, you just have to make sure they don't reproduce.  There are all kinds of ways to make dysgenic breeding unattractive, we haven't even gotten started yet.

Randall Parker said at September 2, 2013 10:56 AM:

The smart aren't making as many babies:

Furthermore, more educated men have more biological children than do more educated women. Results also show that intelligence decreases the number of offspring and frequency of sex for both men and women.

As for instincts for babies: Why do women want babies more than men do?

Nick G said at September 3, 2013 11:01 AM:

Do we know that women want babies more than men?

The cultures that have the highest birth rates are those where women have the least power...

Bob Jenkins said at September 6, 2013 6:42 AM:

Consider having the government offer significant welfare only to people who can't/won't have kids.

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