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Study reveals average age at conception for men vs. women over past 250k years

phys.org

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Re: Study reveals average age at conception for men vs. women over past 250k years

#31

Post by BerislavLopac »

tanbog5 wrote: post #29
bufferoverflow wrote: post #14

Tbh, I thought in early humans females got pregnant at 12-15. Simply because that when they begin to have the capability to have kids.

I know that's a common conception about the past, but what's the actual evidence for it? 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" wi…

Of course they did, which is how silphium got to be extinct. https://en.wikipedia.org/wiki/Silphium

Re: Study reveals average age at conception for men vs. women over past 250k years

#32

Post by wolverine876 »

mertd wrote: post #8

Somewhat grim, but this has to be disregarding the humans who never reach the reproductive age or the ones who cannot keep their offspring alive. So there is some survivorship bias baked into the methodology.

It frustrates me that people on HN, an intelligent crowd, draw conclusions without a serious basis. Why not ask,

'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.

Re: Study reveals average age at conception for men vs. women over past 250k years

#33

Post by jareklupinski »

georgeoliver wrote: post #7

The link to the paper wasn't loading for me. But I would love to see the reasons for extrapolating present-day biology back 250k years?

curious... did your firewall also light up when trying to access the link?

Re: Study reveals average age at conception for men vs. women over past 250k years

#34

Post by refurb »

bufferoverflow wrote: post #14

Tbh, I thought in early humans females got pregnant at 12-15. Simply because that when they begin to have the capability to have kids.

At least for other mammals like elephants, primates and lions, breeding doesn’t start with sexual maturity, at least for males.

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?

Re: Study reveals average age at conception for men vs. women over past 250k years

#35

Post by MobiusHorizons »

wolverine876 wrote: post #32
mertd wrote: post #8

Somewhat grim, but this has to be disregarding the humans who never reach the reproductive age or the ones who cannot keep their offspring alive. So there is some survivorship bias baked into the methodology.

It frustrates me that people on HN, an intelligent crowd, draw conclusions without a serious basis. Why not ask, ' 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…

As I understand it, what the OP is saying is not something any study could ever control for without perfectly preserved DNA from a statistically significant sample of DNA from human populations going back to old generations. Any study that uses DNA collected from modern humans will weed out the DNA of humans whose descendants are not living today. Hence survivorship bias.

Re: Study reveals average age at conception for men vs. women over past 250k years

#36

Post by asgraham »

tanbog5 wrote: post #23
mertd wrote: post #8

Somewhat grim, but this has to be disregarding the humans who never reach the reproductive age or the ones who cannot keep their offspring alive. So there is some survivorship bias baked into the methodology.

If I understand the method correctly, they are actually determining the age that the sample's parents generated dna material that went on to create them. So everyone who has a parent is included - which is everyone who ever lived.

They can't possibly be working with genomes spanning the past 250k years--- the oldest known human remains are only estimated to be ~230k years old, and I doubt they have parent/child trios nicely spanning the intervening few hundred thousand years. So they have to be working on mutation rate inferences.

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/

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4750478/

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5161557/

Re: Study reveals average age at conception for men vs. women over past 250k years

#37

Post by bufferoverflow »

xeromal wrote: post #19
bufferoverflow wrote: post #13

Earlier quoted context omitted.

No, zero is when you're born. Conception is ~9 months before that.

So -9 months old?

9 months from conception.

Age is measured from birth.

Re: Study reveals average age at conception for men vs. women over past 250k years

#38

Post by usrusr »

wolverine876 wrote: post #32
mertd wrote: post #8

Somewhat grim, but this has to be disregarding the humans who never reach the reproductive age or the ones who cannot keep their offspring alive. So there is some survivorship bias baked into the methodology.

It frustrates me that people on HN, an intelligent crowd, draw conclusions without a serious basis. Why not ask, ' 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…

The study seems to look exclusively at the outcome in the contemporary gene pool. And not at archeological DNA samples, because then the x axis would be in years not in generations. There's nothing to compensate for or disregard, the study simply does not claim to describe anything it cannot (very indirectly) see.

Re: Study reveals average age at conception for men vs. women over past 250k years

#39

Post by usrusr »

pugets wrote: post #22
bufferoverflow wrote: post #14

Tbh, I thought in early humans females got pregnant at 12-15. Simply because that when they begin to have the capability to have kids.

To my understanding, if one mother birthed 3 children at ages 15, 20, and 25, then her age of conception would be 20. So it could be the case that women did become mothers in their teens if they also continued bearing children into their late 20s.

And if they got more successful at bringing those children to adulthood with each try (a pattern frequently seen in animals), the visible average resulting from that 15, 20, 25 example would even be higher than 20.

Re: Study reveals average age at conception for men vs. women over past 250k years

#40

Post by pronlover723 »

sdwr wrote: post #3

A lot to unpack (read - wildly speculate about) here. 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 daw…

I watch a lot of old movies (30s-40s-50s). A ton of them have a 40s-50s man marrying a 20s woman.

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

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