Study reveals average age at conception for men vs. women over past 250k years
phys.org
phys.org
To me it reads like someone bought a cheap e.g. lux meter, realized it was highly thermally sensitive, and instead of throwing it out or making a better one, declared they could use it to sense both light levels and room temperature.
Children's DNA inherited from their parents contains roughly 25 to 75 new mutations, which allows scientists to compare the parents and offspring, and then to classify the kind of mutation that occurred. When looking at mutations in thousands of children, IU researchers noticed a pattern: The kinds of mutations that children get depend on the ages of the mother and the father.
Later: Hahn, Wang and their co-authors built a model that uses de novo mutations—a genetic alteration that is present for the first time in one family member as a result of a variant or mutation in a germ cell of one of the parents or that arises in the fertilized egg during early embryogenesis—to separately estimate the male and female generation times[...]
So, it is saying it can measure results for male and female parents separately. But can their analysis of the "kinds" of mutations tell the difference between e.g. "30yo mother, 45yo father" or "20yo mother, 30yo father, plus lots of environmental factors that increase mutations"? The article doesn't make that clear to me.
The article links to the study (at "10.0.4.102" instead of a domain name?), but the link doesn't load... Ok, there is a working link at the bottom: https://www.science.org/doi/10.1126/sciadv.abm7047
I skimmed the study around all the matches for the strings "mutat" and "environ", and this was the best I found: Estimates of the error in our model fit do not show increasing error with either genetic or geographic distance from Iceland (figs. S6 and S7), the origin of the pedigreed mutation data used to train our model. Such a trend may have been expected if differences in mutational spectra were driven by genetic or environmental differences among populations.
The last sentence is actually ambiguous, but I think it's saying "If environmental factors tended to mess with mutational spectra, then we might expect to see X, which we did not see." It's still not clear to me how possible it is for there to be environmental factors that generate the same mutational patterns as higher age. And the only other "environ" match is in a sentence about what affects the age at which people have children.
The answer to GP's objection is not explained in the linked article, as far as I can tell.
The writers of a research paper have a vested interest in seeming smart and displaying their findings as a novel contribution to the greater corpus of research. It's better to think skeptically and critically about any new research paper than to accept it as fact.
Science Advances is open access, so no subscription is required. For those looking for the article: https://www.science.org/doi/10.1126/sciadv.abm7047
An analogy for this one could be saying something like “I know it sucks when people say unkind things, but I think you’re stupid.” Acknowledging the problem does nothing to prevent it or resolve it. It just means at some level the person knows what they’re doing is wrong, and they aren’t self-disciplined or integrated enough to stop.
It burdens the (numerous) other parties with the effort, in the same way scientific results like this do.
[…] average age at conception […]
10,000 generations ago. Like the next one but less of a "solved game".
1000 generations ago - Old men coupling with young women reads as small-scale tribal society to me. Polygamy, pride-of-lions. Groups are small enough that village elders control the, uh, means of production. The bottleneck on food is natural stocks.
200-300 generations ago lines up with the dawn of civilization and large-scale farming (5-7000 years ago). The bottleneck on food is human labour. Young people are encouraged to start (reasonably) self-sufficient farming families, and the surplus is traded for, taxed, or stolen.
0-50 generations ago (1000AD+) ??? Cultural escape velocity is reached. Women are having children later than ever before, pointing to less risky lives, greater food security, and increased autonomy, but also a heavier load of cultural baggage. Becoming elves isn't all it's cracked up to be.
Also, before someone else says it, blah blah blah average vs median.
No idea if that was societal norm, mens fantasy, or whatever. I have to kind of believe movie execs would want the largest audience and so if 40s-50s men dating 20s women was not appealing to women of the time they'd been losing 1/2 the market. But, maybe these particular movies were the male equivalent of romance novels which seem to be written 99% for a female audience
Some examples:
The Girl Can't Help It (1956)
South Pacific (1958)
My Fair Lady (1964)
The Far Country (1954)
Casablanca (1942)
To Have and Have Not (1944)
Charade (1963)
There are literally 100s of them and I'm not recommending any of the movies above per-say, but it does stick out to me just how common that theme is of man, at least 15yrs older than woman which I believe is less common today
https://www2.census.gov/programs-surveys/demo/tables/familie...
Because men can have attractive roles past 40 and women not, or only very rarely. I don't remember the name of the movie, but it was about greek and a female character that was 40, but the cast was not offered to a 40 year old, but a 30 year old.
Because 40 year old women are not supposed to look like 40 year olds, which is where we are back to the fantasy thing.
Biology is a real thing, though, men can become fathers with over 50, but women cannot. So I am not judging btw. But those fantasies are real and strong, even though they are taboo nowdays.
Poking at US presidents that stood out (i.e. more than 5 years):
| President | Born | Spouse| Delta |
|-----------|-------|-------|-------|
| Biden | 1942 | 1951* | 9 |
| Trump | 1946 | 1970* | 24 |
| Reagan | 1911 | 1921* | 10 |
| Kennedy | 1917 | 1929 | 12 |
| Eisenhower| 1890 | 1896 | 6 |
| Wilson | 1856 | 1872* | 16 |
| Harrison | 1833 | 1858* | 25 |
| Cleveland | 1837 | 1864 | 27 |
| Arthur | 1829 | 1837 | 8 |
| Hayes | 1822 | 1831 | 9 |
| Lincoln | 1809 | 1818 | 9 |
| Fillmore | 1800 | 1813* | 13 |
| Polk | 1795 | 1803 | 8 |
| Tyler | 1790 | 1820* | 30 |
| Q. Adams | 1767 | 1775 | 8 |
| Monroe | 1758 | 1768 | 10 |
| Madison | 1751 | 1768 | 17 |
| Adams | 1735 | 1744 | 9 |
*: latest marriage
> The first time you marry for love, the second for money, and the third for companionship.
But as far as I observe, this is frowned upon today. It still exists of course, many of the hollywood heros regulary change their 20 year old models for partner, but there is increasing criticism about it. I mean, my partner is 7 years younger and even this was met with criticism.
Erm, because I live in this society, so the social norms of this society do affect me and well, everyone else in it. I thought that is obvious.
It was well known that Hollywood had an age discrimination problem for women up until the mid or late 80s or so.
Like a really well known problem where women couldn’t get leading roles after a certain age. It was a well publicized thing and just kind of common knowledge.
The reason for that is that 2 of them died in child birth. Modern medicine is a wonderful thing.
Plus, movies always operated in fashions. What was depicted was heavily limited by big studios policies and by mandated codes. These limited topics and the way things were shown.
Movies are not reality and never were. They don't depict real life now either.
I’m used to the idea of actors and weird new age dudes doing it in the US, but it seems rare for normal people.
Same thing with 50 year old men with 20 year old wives. I am in my early 40s and there is no way I will marry woman in her early 20s, unless she is very special. Sure, 20 year old bodies are attractive, but maturity difference is too great. The movies are fantasies, showing off women at the age of peak physical attractiveness, with just enough immaturity to make the man feel more responsible by contrast, but without any of the quirks of actual immaturity.
Having a 20 year old sex partner is another story. And many women are willing to let you live your fantasy, for a time, for a price...
I daresay you won't find a George from Seinfeld in there, rather a set of George Clooneys.
I don't doubt that there was an age difference, but we have/had plenty of living couples from that era and can look in the census records - were Spring/Fall marriages that common?
Even if average age in a relationship was symmetric, men being fertile for longer would cause age at (child's) conception to be higher for men. That effect needs to be untangled before we can know just how much men preferred younger women in the past/vice versa.
It happens in real life too - successful older men being with much younger females is normalized by society and a common sight. The opposite not so much though.
Also those movies are from the days where only a handful of movies were made every year, so the lack of competition meant you could write anything and jam it down people's throats, rather than needing to follow demand.
tldr: America is a woman's dating market but the odds are better stacked for men once you leave the country.
I bet 100k years ago, some women were pregnant yearly, from teenage to menopause.
If men were begetting from a young age 100k years ago, and most of their children died until they were older and more experienced, those early children are lost from the DNA record.
But if there were several independent strands to support it it would give it more credence.
If you stand by your assertion, please provide evidence.
Those would be some natural selection processes, and they don’t apply to us in any significant way since.. I would say the agricultural revolution at least, but maybe even sooner (the very reason we can “feed” such a hungry organ as our brains is due to our efficiency at hunting/processing food even back then thanks to tools/fire)
That's culture, not evolution. It's absolutely natural (in every sense of the word) and there are biological components.
Outside of that, though, there is also physical natural selection that occurs. Human "hardware" is evolving along with the "software".
But the point is, evolution is not a “thing”, it is an observation explained by selection pressures, an emergent property if you will. The characteristics/statistics for people are way different than any other wild animal, so I think it is fair to attribute that to society vs nature.
There are many modern scientists who don't understand evolution.
A. I doubt there are many who don't understand natural selection and/or want to talk about evolution without understanding it
B. I excluded those people explicitly, so what's your point?
Of course, even for this definition human evolution is absolutely not "completed" at the moment, since however fit/adapted homo sapiens were to the conditions of Africa 200 000 years ago, the last few thousand years have seen enormous changes in our environment to which we definitely haven't adapted yet in the insignificantly small span of 100 or so generations; If the major changes in our social and physical environment would stop today, perhaps we might reach some evolutionary "stable spot" in a 100 000 years (or much more), but right now we haven't even fully adapted to agriculture, much less modern conditions.
And similar genetic studies work on other species so that's even more evidence it's reasonable generic a technique.
After the first world war, for example, a large number of young men were gone. You can see the memorials with names on in any town or city in Europe.
The women of that generation would have competed with older women for older men as potential partners if they wanted children.
I was watching some random show where they were talking about the reproduction rates in the former Soviet Union and large events (like world wars) have lasting effects on birth rates that echo through time approximately every twenty years.
There's power asymmetry, people are monsters and sexual predation is rampant but there's also biological feasibility at play here.
To demonstrate, let's say that we have an imaginary equalityville where for every age pairing and sex act, there is an exactly equal one with the ages swapped - as in mathematically perfect equality.
In equalityville occasionally 45 year old men sleep with 35 year old woman. But every time, a 45 year old woman sleeps with a 35 year old man, coincidentally, at the exact same time, doing equal things, in another part of town.
However, 45 year old woman give birth rarely. Let's say it's 1/99th the rate of the 35 year olds.
So there's
1000 45 year old women with 35 year old men resulting in 10 births
1000 45 year old men with 35 year old women resulting in 990 births
Now we're going to calculate the average age based on the babies.
Women (990 * 35 + 10 * 45)/1000 = 35.1
Men (990 * 45 + 10 * 35)/1000 = 44.9
And thus we get our paradox because we're counting by live births. So long as there are age delta pairings past some set of constraints, the male average will drift upward.
It'd be interesting to normalize for that. This is probably doable since actual fertility statistics are well studied.
The takeaway here is that straight single middle aged men who chase after woman, are on ok cupid looking for them, and who fill out this survey, are on average, looking for younger women.
Those results cannot be seen as representative of the general population based on the methodology used here.
It gets worse. Similar to the Alf Landon flaw, this could simply be exposing the demographic makeup of the site. Perhaps men think there's a promise on okcupid of younger women so it self-selects for those proclivities. Perhaps women think there's a different promise so they come accordingly.
You have to extricate that. Otherwise, it'd be like going to a gay dating site, running a survey and then come out with some earth-shattering ground-breaking claim of 100% of men saying they prefer intimacy with other men. I mean, duh, look who you're asking.
That's not to say these results don't hold generally, they might. But this is not evidence supporting that.
Younger women are more fertile.
There's nothing more to it than that. This dynamic has existed for so long it's part of our DNA now via sexual selection.
One were women were treated as sexual resources to be taken and controlled
Another with more free will.
In both cases, sexual selection would lead the offspring of those that aligned with the dominant male and his group, through free will or coercion, to have greater survival odds due to the dominant male's ability to control or capture resources, or fend off danger.
If you're aware that a majority of stone-age societies practiced communism without hierarchies for several tens of thousands of years to offset this sexual selection, I'd be interested to hear about that period of history.
https://en.m.wikipedia.org/wiki/The_Dawn_of_Everything
Regardless what you think of the text, even the most stubborn critics agree the classical claims lack critical support.
You don't have to assume communism. A world requiring lots of labor to do basic things with lots of diseases and death being common is alien to us. I don't realistically need to worry about wild animals, water access, food availability, or succumbing to unfortunate weather.
DNA studies show that human population may have been as low as 2,000, on the brink of extinction 70,000 years ago.
This time period is so vast we're talking neanderthals and a bunch of other hominids.
It's a wildly different structure. There was lots of diversity. I assumed no social structure in my claims and showed that regardless of social structure, that pattern would arise as an artefact of the biology of childbirth.
If you can demonstrate the delta is larger than biologically expected, then you have something to back structural claims. But that's you know, actual academic work that would take a month or twenty. We aren't going to resolve that here. The childbirth argument was the easy one.
So everyone who has a parent is included - which is everyone who ever lived.
From a non-expert reading of the article, their pipeline is more like: modern human population genomes -> estimates of modern mutations' ages -> estimate of average historical parental ages.
The first estimation (genome -> mutation ages) was carried out in a prior study "GEVA" [1], and this paper's contribution seems to be estimating the average parental ages based on those previously estimated historical mutation rates.
I couldn't find any mention of using old DNA samples. The GEVA study pulls from two genome databases, TGP [2] and SGDP [3], both of which seem to be entirely modern genomes. I'm not an expert in the field, so maybe it's obvious to a population geneticist that these databases do include old genomes.
Given that they're only using modern (surviving) genomes, the critique of survivorship bias seems valid.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6992231/
'Is this study disregarding the humans who never reach the reproductive age or the ones who cannot keep their offspring alive? Is there is some survivorship bias baked into the methodology?'
You might find out - we might find out - rather than you guess wrong, never find out, and we all carry the error with us.
Problem is, the internet is also filled with studies that prove or disprove anything you want, best to be skeptical.
I personally don't put much credence into any studies that seriously thinks they can make any factual accurate statements about things that may or may not have happened 250,000 years ago. Science is never settled.
From the comments, it is pretty clear to me that people lack understanding of biology/modern computational genomics, and the models used and their limitations.
"Average age of people who gave birth include people who never give birth?" or "Is a selection bias to include only people who gave birth in the selection of people who gave birth" sound completely different if asked this way, right?
TIL: I must be having a past life regression
So that log mark ~110 gen ago is ~3k BP.
A particular civilization doesn't last in a recognizable or functional form more than about 10 gen.
"The median age at menarche was 14.5 years (95% CI=14–15; Nindividuals=128; Nobservations=199), which is within the range of variation of modern populations."
There are plenty of social and religious norms even today that keep people from getting together too young.
There's also no reason not to think people at the time understood how sex and pregnancy worked. They didn't have the internet but they were as intelligent as we are today. I'm sure they could figure out how to have "fun" without always having kids.
> The plant may also have functioned as a contraceptive and abortifacient.
You are far more confident on this than Wikipedia. Are you an expert on it?
Biological fertility as a baseline only slightly modified by social norms seems to be a good guess.
And Juliet was considered way to young to marry (we don’t really know how old exactly Romeo was).
While mid-teens was acceptable age in many cultures to marry and have children by the 17th century that wasn’t really the case. e.g. the average age at first marriage for women was 24 in England in the 1600s
I mean sure, could count as "evidence" but you'd have to be aware of the strength of it.
Imagine in a 100 years time, the next civilisation finds some popular dvd and tries to draw conclusions from it.
Also, I think quite a lot can be reconstructed from even primitive drawings, let alone a whole dvd we know got popular and thus even more relevant for an age.
I do agree with you about getting information from even primitive drawings. I think we differ in our views about the degree and type of information we can get.
Older, higher ranked males control the breeding rights. Males often have to either fight for status or separate from the group and create their own breeding pool.
Wouldn’t be surprised that humans do something similar in early cultures since they tend to have highly organized societies, even for females?
Looked around in the literature. Apparently consensus is that paleolithic hunter-gathers had menarche earlier than agricultural groups. Around the same age as the current averages in developed countries.
Dare I say it, and this may just be not right, Genghis Khan is purportedly supposed to have fathered thousands of children it is said he had 500 or so secondary wives (citation needed).
Since average (mean) income is famously a bit pointless due to a few very rich people, wouldn’t father’s age at conception be similarly effected?
1. No man wanted to raise another's child (as far as evolution is concerned, that doesn't lead to replication of ones own genetic material)
2. Less risk of VD, which would seriously affect your ability to utilise the harem