PILOT SPIN
Spin Zone => Spin Zone => Topic started by: Jim Logajan on March 27, 2025, 11:03:08 AM
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That’s interesting, but he doesn’t talk about what the reasons might be for the decline in fertility rates all over the world.
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That’s interesting, but he doesn’t talk about what the reasons might be for the decline in fertility rates all over the world.
He probably couldn't because the science isn't settled. It seems that a certain class of species self-limit their own populations as they near the resource limit of their local environment. Another class has the classic exponential population growth (such as bacteria) that eventually causes the population to exceed the carrying capacity of their environment, followed by large population drop. Then the cycle begins again, assuming the environment recovers enough to allow it to repeat. On the other hand self-limiting class of species population may oscillate near the carrying capacity of their environment rather than huge variations.
A theory in biology calls the two classes of species K-strategists (e.g. wolves and humans) and R-strategists (e.g. bacteria). It is a simple theory and therefore has flaws, but is still taught - this seems a good brief explanation: R-strategists, K-strategists and Survivorship curves: The reproductive adaptations of different organisms (https://eco-intelligent.com/2018/07/30/r-strategists-k-strategists-and-survivorship-curves-the-reproductive-adaptions-of-different-organisms/)
I first learned of the theory about 23 years ago from a physicist(!) who happened to be fond of wolves. Turns out wolves self-limit their populations once they reach the limit of their geographic area. Much research has been done to figure out HOW they self-limit. Some papers that show some theories and disputes:
Wolves Naturally Limit Their Own Numbers (https://nywolf.org/2019/01/wolves-naturally-limit-their-own-numbers/)
DO WOLVES CONTROL THEIR OWN NUMBERS? (https://wolf.org/wolf-info/factsvsfiction/do-wolves-control-their-own-numbers/)
Do wolves control their own numbers? Understanding and updating the long debate (https://nsojournals.onlinelibrary.wiley.com/doi/10.1002/wlb3.01299)
Lastly, prior to modern transportation human populated remote islands tended to reach their carrying capacities relatively quickly and for those population to survive for hundreds or thousands of years requires some sort of self-limiting. I found one site that discusses examples of how that was allegedly done:
Do three Pacific islands provide lessons for achieving a sustainable human population? (https://overpopulation-project.com/do-three-pacific-islands-provide-lessons-for-achieving-a-sustainable-human-population/)
I'd prefer some better site to reference, but all I could find with simple searches.
As to modern fertility decline: my own theory is that technological progress has allowed human contentment in first world countries to reach satiation with the result that fewer people look to starting a family as a means of finding contentment.
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Did any of y'all ever watch the movie Mid Sommer?
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That’s interesting, but he doesn’t talk about what the reasons might be for the decline in fertility rates all over the world.
Mousetopia theory. Some guy did an experiment with mice, putting a couple of them in an environment with plenty of resources. They rapidly multiplied but reached a point where their reproduction self-destructed and they ended up dying off completely. He replicated the experiment several times with the same result but no one else has attempted to duplicate it.
The theory, applying to humans, is when you become prosperous, it triggers some primitive mechanism in us to stop reproducing so that we don’t overpopulate and use up all the resources. But the question is, why doesn’t the de-population self limit? In the case of the mice, they depopulated themselves into extinction.
The mechanisms were combinations of behaviors such as males losing interest in sex, isolating themselves, or joining gangs going around attacking other males or attacking and killing any breeding female, and females losing interest in caring for their babies.
In humans, we have lots of babies when impoverished which is counterintuitive. The richer we become the fewer babies we have. You’d think we would have more because we can afford them but apparently our DNA is hardwired to reproduce like crazy when faced with threat of starvation and to cut way back when assured a rich future.
Maybe in our evolution we have never faced a world of technological progress assuring we never run out of food and so never evolved brakes on the depopulation strategy because another famine was always right around the corner to get us reproducing again.
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Did any of y'all ever watch the movie Mid Sommer?
Don’t think so.
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Do three Pacific islands provide lessons
Wow! I’d never heard of Sirayans or massage abortions before, and I was a childbirth educator, well versed in all obstetrics at least in the West, over the past two centuries. I knew there were herbal abortifacients. But it makes total sense. At least directly postpartum, massage of the uterus increases oxytocin secretion and contraction of the uterus cutting off blood (preventing hemorrhage) and enabling discharge of the placenta, and term women have attempted to jump start labor by massaging their bellies, so I suppose massaging it very early in pregnancy can begin it contracting. Just never knew primitive people knew this and actually used it to cause abortions.