In regards to famines:
A 59% male ratio is a huge demographic shift. I really can't believe that they wouldn't have noticed in that incident alone. I suspect it would also have shown up in parish records from the Irish potato famine. Keeping track of births doesn't really take high tech databases: it takes a lot longer to produce a baby than to write out it's birth certificate in longhand.
Regarding sex ratios, the classic example is the elephant seal: a highly polygamous species where a male maintains a harem of up to 100 females. People often intuitively expect that therefore an elephant seal will produce more female offspring than male. In fact though, they produce a 50-50 ratio, even though most of the males will never reproduce.
The reason is that every offspring has exactly one male parent and one female parent. The reduced number of males who reproduce is therefore exactly compensated by the increased success of those that do manage it. It's the one-mummy one-daddy thing that determines sex ratios, and that means there's a strong evolutionary pressure to keep the numbers pretty even.
If things worked the way the study says and you had a hard few years: maybe due to famine, maybe the local wildebeest have died off, maybe another tribe's forced you off the good land, then you'd have a generation with a skewed sex balance, producing fewer offspring in the subsequent generation. (That's not a group selectionist argument: producing a kid the same sex as everyone else's kid hurts the individual as well as the group).
This supposed effect just doesn't make sense to me.--"Everything is vague to a degree you do not realize till you have tried to make it precise." -- Bertrand Russell[ Parent ]
Remember that the evolutionary pressure you talk about is to produce an even sex ratio at breeding age. That's not the same as producing an even sex ratio at birth.
The other thing to consider is that the study you labeled bad science was looking at slight changes in diet, not starvation. It is very possible that the effect goes away when people are literally starving. There's a huge difference, biologically, between skipping breakfast and going five months without enough food.---- ウセーバラケダ[ Parent ]
If you have a skewed sex balance in which females are overrepresented, you don't necessarily produce fewer offspring in the subsequent generation.
They claim that the reason behind is is that boys are more expensive to produce than girls. If so, the effect ought to be more pronounced the greater the degree of famine.
The study was of 740 women. Not a tiny sample, but a few hours with Excel can easily produce as many statistically significant correlations from random data as you can be bothered to generate. Meanwhile, famines like Dutch hunger winter, the Soviet famines, the Irish potato famine affect hundreds of thousands, maybe millions. I'm betting on the bigger samples.--"Everything is vague to a degree you do not realize till you have tried to make it precise." -- Bertrand Russell[ Parent ]
In a famine, at whatever level of starvation this effects shows up at, there would be some people at this level, which means the effect would show up demographically.--"Everything is vague to a degree you do not realize till you have tried to make it precise." -- Bertrand Russell[ Parent ]
Remember this effect allegedly exists to help women produce smaller girl offspring when short of calories. Yet somehow in a situation when people are genuinely short of calories, it's so small as to be statistically indetectable with a sample size in the hundreds of thousands. Yet it shows up in a sample of hundreds when considering prosperous, well-fed mothers in the developed world. And it doesn't affect the sex ratios born to the overweight and obese: that would surely have shown up by now too.
It doesn't make sense: an economy measure that only shows up when there's a miniscule deviation from a healthy food intake, disappearing completely whenever there's a significant calorie surplus or deficit. --"Everything is vague to a degree you do not realize till you have tried to make it precise." -- Bertrand Russell[ Parent ]
If there is any effect in humans, it must be pretty tiny to have not shown up by now.
It works in rodents of course. Rodents are highly optimized to grow fast, pump out a load of babies and expire, so there's plenty of room for life-extension trade-offs. But humans take about 13 years to get to reproductive age, and 25 before the brain fully matures. Having invested all that time maturing, evolution needs us to take advantage of it. It's a pretty fair bet that we're already got all the easy life-extension genetic switches and mechanisms turned all already.--"Everything is vague to a degree you do not realize till you have tried to make it precise." -- Bertrand Russell[ Parent ]
See here.---- ウセーバラケダ[ Parent ]
The "Effects on humans" section basically just talks about the normal ill-effects of being overweight. When it does cite actual scientific papers about calorie-reduced life-extension in humans it's papers like this: "Why dietary restriction substantially increases longevity in animal models but won't in humans."
That paper bears out the earlier point: there's a trade-off between fast reproduction and longevity. Humans have already traded off for that: we reproduce very slowly and live very long lives. Any life-extension effects of this in humans are likely to be noexistent or very small.[ Parent ]
But this story seems a bit different. I'd like to see a reconciliation of the one I'd heard (a relative wealth situation) and the one presented in those articles.[ Parent ]
If you look up what they call Pathological Science or Voodoo Science, not all of the features but a disturbing number of them seem to apply to sociobiology.
1. Discoverers make their claims directly to the popular media, rather than to fellow scientists. 2. Discoverers claim that a conspiracy has tried to suppress the discovery. 3. The claimed effect appears so weak that observers can hardly distinguish it from noise. No amount of further work increases the signal. 4. Anecdotal evidence is used to back up the claim.
2. Discoverers claim that a conspiracy has tried to suppress the discovery.
3. The claimed effect appears so weak that observers can hardly distinguish it from noise. No amount of further work increases the signal.
4. Anecdotal evidence is used to back up the claim.
Anthropologists, historians and social scientist have spent an awful lot of time and effort painstakingly eating grubs with remote tribes, spending lifetimes analysing gravestones and parish records and so on; and applying the incredibly sensitive pattern-recognition system of the human brain to the resulting data.
I wish biologists who venture into their realm would start looking at their data, instead of just assuming that as mere social scientists they're just too thick to have done anything worthwhile. --"Everything is vague to a degree you do not realize till you have tried to make it precise." -- Bertrand Russell[ Parent ]
