The heritability of fertility makes world population stabilization unlikely • Hacker News Board

Re: The heritability of fertility makes world population stabilization unlikely

#51

Post by _liww » Fri, Jul 05, 2019, 11:35 AM UTC

andybak wrote: post #5

Could someone with more time than me summarize how they reached the conclusion that fertility was heritable? It seems very counter-intuitive unless I'm misunderstanding the precise meaning of "heritable" that enables them to draw this conclusion.

The three law's of behavioural genetics:

“First Law: All human behavioural traits are heritable.

Second Law: The effect of being raised in the same family is smaller than the effect of the genes.

Third Law: A substantial portion of the variation in complex human behavioural traits is not accounted for by the effects of genes or families.”

Beyond that though, the genetics of human fertility is pretty well understood. Here's a (now fairly old: from 2016) GWAS study on human reproductive behaviour: https://www.ncbi.nlm.nih.gov/pubmed/27798627

They show genetic correlations between reproductive traits and other behavioural traits in Figure 3. You might find it helps you develop an intuitive understanding. Happy to answer questions if you have any.

Re: The heritability of fertility makes world population stabilization unlikely

#52

Post by _liww » Fri, Jul 05, 2019, 11:38 AM UTC

aluren wrote: post #43

j_wtf_all_taken wrote: post #41

The authors seem to have a background in economics, does that really fit the research topic of that paper?

A lot of people love to chime in about "genetics" or "heritability" despite having no background in actual genetics (no, evopsych or behavioral "genetics" don't count) and publish in low-impact factor journals that are virtually unknown in the actual genetics community (or derided as a joke, like plos one). I'm not sure what to make of this paper to be honest.

What you should understand is: most geneticists wouldn't have had the balls to write this even though it's obvious to them. Someone did have the courage to write it. Now wrap your head around what they wrote.

Re: The heritability of fertility makes world population stabilization unlikely

#53

Post by _liww » Fri, Jul 05, 2019, 11:41 AM UTC

j_wtf_all_taken wrote: post #42

j_wtf_all_taken wrote: post #41

The authors seem to have a background in economics, does that really fit the research topic of that paper?

One of the sources: https://journals.plos.org/plosone/article?id=10.1371/journal... >> This finding implies that individuals with genetic predispositions for an earlier AFB had a reproductive advantage and that natural selection operated not only in historical, but also in contemporary populations. The observed postponement in the AFB across the past century in Europe contrasts with these findings, suggesting an evol…

Because that never happened before in human history:

https://www.amazon.com/s?k=Who+We+Are+and+How+We+Got+Here&re...

Re: The heritability of fertility makes world population stabilization unlikely

#54

Post by sadris » Fri, Jul 05, 2019, 11:43 AM UTC

danieltillett wrote: post #9

marliechiller wrote: post #2

admittedly i havent read the whole article, only the abstract, but: assuming that children from larger families will partially inherit the trait for having larger families themselves seems like a leap to me - arent family sizes in less developed societies generally considered to be either due to religious superstition or because more children = more workers to provide for the family a la victorian times? Once these f…

In this case it doesn't matter if fertility is genetic or environmental. Parents can pass on the trait either socially or genetically, or as almost is certainly the case as a combination of the two.

In almost every case, parents do not pass traits socially. Shared environment impact is roughly zero in nearly every trait ever examined.

Re: The heritability of fertility makes world population stabilization unlikely

#55

Post by sadris » Fri, Jul 05, 2019, 11:47 AM UTC

adrianN wrote: post #39

0xd171 wrote: post #34

Earlier quoted context omitted.

Isn't your reasoning backwards? We know that improvements in living conditions lead to reduced fertility. And climate change will worsen living conditions, not improve them. So if areas with poor living conditions have high fertility now, why would even worse conditions (due to climate change) reduce their fertility? Sure, the outcomes and quality of life of the children will be even worse than it is but I can't see…

Sufficiently bad conditions lead to children starving and women not surviving labor.

In bad conditions humans breed more. There was a ten year famine in Ethiopia yet there wasn't a single year in which the population actually dropped. People stop breeding when they know their offspring will survive

Re: The heritability of fertility makes world population stabilization unlikely

#56

Post by ImprovedSilence » Fri, Jul 05, 2019, 11:52 AM UTC

bad_user wrote: post #14

All of my grandparents come from big families. My grandmother on my father's side comes from a family of 12 children. Yet my grandmother only had 4 children and my father only 2, and now I only have 1. This is an anecdote, but I don't think heritabiliy has anything to do with it. Large families simply happen due to poverty. When poor, you want more children because there's strength in numbers. Plus the women are stay…

While not “necessarily” poverty related, I read somewhere once that India wanted to bring TV to as many rural households as possible. The reasoning being is that People are not having kids because cheap labor, they’re having kids because there is nothing else to do at night for entertainment, and contraceptive use is non existent.

Re: The heritability of fertility makes world population stabilization unlikely

#57

Post by FeteCommuniste » Fri, Jul 05, 2019, 12:02 PM UTC

car12 wrote: post #29

acqq wrote: post #26

Earlier quoted context omitted.

I suspect that “Southeast Asian” women observed had different religion than those where “fertility pattern of their parents” is preserved. Not all religions have the same effect on the outcomes, ignoring that in the studies is misleading.

What it is pussyfooting around is that there is not that drastic of a drop in fertility rates of muslims. I guess it shouldn't be hard to conceive where Islamic parties start having a major voice in elections because of demographics.

Fertility rates across better-developed majority-Muslim countries have been plummeting: https://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&...

Not quite to the extent of some white European populations, sure, but very far from the "breeding like rabbits" image that politicians use to drum up fear among uninformed voters.

Re: The heritability of fertility makes world population stabilization unlikely

#58

Post by barry-cotter » Fri, Jul 05, 2019, 12:02 PM UTC

andybak wrote: post #5

Could someone with more time than me summarize how they reached the conclusion that fertility was heritable? It seems very counter-intuitive unless I'm misunderstanding the precise meaning of "heritable" that enables them to draw this conclusion.

Every other psychological trait is heritable[1], why wouldn’t desire to have children be?

[1]http://humancond.org/_media/papers/bouchard04_genetic_influe...

Genetic Influence on Human Psychological Traits

There is now a large body of evidence that supports the conclusion that individual differences in most, if not all, reliably measured psychological traits, normal and abnormal, are substantively influenced by genetic factors. This fact has important implications for research and theory building in psychology, as evidence of genetic influence unleashes a cascade of questions regarding the sources of variance in such traits. A brief list of those questions is provided, and representative findings regarding genetic and environmental influences are presented for the domains of personality, intelligence, psycho- logical interests, psychiatric illnesses, and social attitudes. These findings are consistent with those reported for the traits of other species and for many human physical traits, suggesting that they may represent a general biological phenomenon.

Re: The heritability of fertility makes world population stabilization unlikely

#59

Post by kikoreis » Fri, Jul 05, 2019, 12:13 PM UTC

ImprovedSilence wrote: post #56

bad_user wrote: post #14

All of my grandparents come from big families. My grandmother on my father's side comes from a family of 12 children. Yet my grandmother only had 4 children and my father only 2, and now I only have 1. This is an anecdote, but I don't think heritabiliy has anything to do with it. Large families simply happen due to poverty. When poor, you want more children because there's strength in numbers. Plus the women are stay…

While not “necessarily” poverty related, I read somewhere once that India wanted to bring TV to as many rural households as possible. The reasoning being is that People are not having kids because cheap labor, they’re having kids because there is nothing else to do at night for entertainment, and contraceptive use is non existent.

Re: The heritability of fertility makes world population stabilization unlikely

#60

Post by barry-cotter » Fri, Jul 05, 2019, 12:14 PM UTC

mxfh wrote: post #11

andybak wrote: post #5

Could someone with more time than me summarize how they reached the conclusion that fertility was heritable? It seems very counter-intuitive unless I'm misunderstanding the precise meaning of "heritable" that enables them to draw this conclusion.

So far the consesus was that migrants from traditonally child rich societies, acclimated already a generation later at local lower levels if prosperitiy and education level was reached as well. So it's the economy and social stability through the state that replaces children as the only "pension and care" provider for retirement. FRANCE: "We show a convergence towards French standards that differs across groups of or…

Desire to have children has been under selection only since the demographic transition. Most of the world has less than two generations of selection, most one, some none. As such we would expect to see a lot of variation in desire to have children. The only group I’d be willing to bet money have notably higher desire to have children than other human populations are the French because that’s where the demographic transition started. For everyone else on average we should expect more or less the same mean and variance.

Then the environment changes in one, or in two ways. People move to another country, or not, and their culture gets exposed to modernity/the demographic transition. If they move to another country the culture they’re surrounded by will change, which will change when their children think it’s appropriate to marry, how many children they want, etc. It will do nothing to their genes, including their desire to have children.

But all over the world the selection is ongoing. As time goes on the proportion of the population that wants lots of children increases and so do the number of large families.

Genetic and sociological explanations can both be true at the same time. Mormons have more children than average for sociological reasons. They value and honour child rearing and family life far, far more than normal Americans. People whose parents had 6+ children also have more children than average, possibly partly due to role model effects, but mostly because they like children. There’s nothing incompatible about these explanations.