How about a counter effect?
Many couples today reproduce with the assistance of reproductive technology. This releases selection pressure, so low-fertility genes proliferate.
The heritability of fertility makes world population stabilization unlikely
61–70 of 154 posts
Re: The heritability of fertility makes world population stabilization unlikely
#62All 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…
If a trait is not strongly selected for but variation exists it will be maintained in the population. See height, hair colour, propensity to gain weight, etc. Then you change the environment so that the trait is under strong selection. The people living in Scandinavia 3,000 years ago couldn’t digest lactose. Now ethnic Scandinavians who are lactose intolerant are basically nonexistent. It’s at above 99% homozygotes.…
If it was advantageous for us to have lots of children, then women would have a dozen at a time, rather than one. There are plenty of mammals that do that. There’s clearly a tradeoff there and the selective pressures for humans tend to lean toward fewer. Not sure where we’ll end up, but time will tell.
Re: The heritability of fertility makes world population stabilization unlikely
#63All 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…
If a trait is not strongly selected for but variation exists it will be maintained in the population. See height, hair colour, propensity to gain weight, etc. Then you change the environment so that the trait is under strong selection. The people living in Scandinavia 3,000 years ago couldn’t digest lactose. Now ethnic Scandinavians who are lactose intolerant are basically nonexistent. It’s at above 99% homozygotes.…
> Large families do not just happen due to poverty
You're right, they happen due to culture. However, the cultures you listed are notably insular and traditional, meaning they do not have large families for the same reason much of the world does (high infant mortality). I doubt these will ever change, but it is very possible the rest of the world will.
Re: The heritability of fertility makes world population stabilization unlikely
#64Earlier quoted context omitted.
If a trait is not strongly selected for but variation exists it will be maintained in the population. See height, hair colour, propensity to gain weight, etc. Then you change the environment so that the trait is under strong selection. The people living in Scandinavia 3,000 years ago couldn’t digest lactose. Now ethnic Scandinavians who are lactose intolerant are basically nonexistent. It’s at above 99% homozygotes.…
If it was advantageous for us to have lots of children, then women would have a dozen at a time, rather than one. There are plenty of mammals that do that. There’s clearly a tradeoff there and the selective pressures for humans tend to lean toward fewer. Not sure where we’ll end up, but time will tell.
I think there was such a selection pressure when we were nomadic hunter-gatherers. Agriculture is a very recent development anthropologically, so we were still in the mode of one-kid-per-pregnancy, though multiple might have been advantageous. It's possible we developed higher fertility due to that, but we didn't have enough time for that new pressure to kick in.
Re: The heritability of fertility makes world population stabilization unlikely
#65Earlier quoted context omitted.
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.
Somewhat related, https://www.conservationmagazine.org/2013/09/tv-as-birth-con...
I'd dispute a lot of what is in that source. Their heat-maps of various characteristics are a correlation only, and a correlation among things which tend to go together (fertility rate, tv ownership (wealth), gdp per capita, and female literacy usually increase in tandem as part of a cultural shift). This does not necessarily mean they cause each other.
Also, ought we really to be brainwashing people to live how we wish them to?
Re: The heritability of fertility makes world population stabilization unlikely
#66Earlier quoted context omitted.
If a trait is not strongly selected for but variation exists it will be maintained in the population. See height, hair colour, propensity to gain weight, etc. Then you change the environment so that the trait is under strong selection. The people living in Scandinavia 3,000 years ago couldn’t digest lactose. Now ethnic Scandinavians who are lactose intolerant are basically nonexistent. It’s at above 99% homozygotes.…
> Large families do not just happen due to poverty You're right, they happen due to culture. However, the cultures you listed are notably insular and traditional, meaning they do not have large families for the same reason much of the world does (high infant mortality). I doubt these will ever change, but it is very possible the rest of the world will.
Though I’m sure the Mormons would cop to traditionalism calling a religion where the median man spent two years of his life in a foreign country insular is slightly odd, considering most Americans never leave their own country. Even aside from that cosmopolitanism Mormons have been state governors and been contenders for the presidency. Insular they are not.
Re: The heritability of fertility makes world population stabilization unlikely
#67All 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…
I can think of, at least, another possible explanation.
Before birth control was available, there is not need for evolutionary effects in the willingness to have children directly, only for the willingness to have sex. You probably agree with me that sexual desire is pretty common, obviously we have evolved for it.
After birth control exist, sexual desire is not an appropriate proxy for evolutionary pressures, so, we could see an increase in the instinct to have children and, maybe, a decrease in the instinct of having a lot of sex.
Re: The heritability of fertility makes world population stabilization unlikely
#68Earlier quoted context omitted.
If it was advantageous for us to have lots of children, then women would have a dozen at a time, rather than one. There are plenty of mammals that do that. There’s clearly a tradeoff there and the selective pressures for humans tend to lean toward fewer. Not sure where we’ll end up, but time will tell.
I think there was such a selection pressure when we were nomadic hunter-gatherers. Agriculture is a very recent development anthropologically, so we were still in the mode of one-kid-per-pregnancy, though multiple might have been advantageous. It's possible we developed higher fertility due to that, but we didn't have enough time for that new pressure to kick in.
It’s been 5,000 years since the dawn of agriculture. If multiple births were fertility increasing they’d be, if not normal, at least common in some groups. You don’t even get 1 in 3. Single births are clearly not being found wanting by the Blind Idiot God.
Re: The heritability of fertility makes world population stabilization unlikely
#69Earlier quoted context omitted.
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.
How is the statistic of lower dipping fertility rates inside Muslim countries of relevance when talking about:
> the "breeding like rabbits" image that politicians use to drum up fear among uninformed voters
The fertility rates of muslim immigrants are far higher than the natives which will lead to a decisive demographic and political shift, which is what those politicians are talking about.
Re: The heritability of fertility makes world population stabilization unlikely
#70This is ridiculous. The replacement fertility rate to maintain population before modern medicine could be closer to ten than two not so long ago. War, famine, disease, accidents, and infant mortality made it so surviving until you were old enough to start having your own children was rare and women were often pregnant or nursing continuously as long as they were fertile. The premise of heritable fertility driving pop…
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> You do not understand evolution
Probably.
But although it is almost tautological that fertility is heritable, it doesn't follow that the first world infertility trend will reverse.
If whatever is causing first world infertility (1) actually profits from our infertility and (2) is some kind of evolving entity itself, we could find ourselves in an evolutionary arms race, and lose.