Wherein you bias the AI to return (or makeup) sources supporting your claim. Most folks marry when they're working age adults, which also are the ages most folks are likely to be fertile, and most folks marry close in age and have since these things have been tracked. The exceptions tend to be countries with political and/or economic instability where girls get little to no schooling. And political marriages where heirs could determine the future of nations.
Almost no cultures check for fertility before marriage, and very few consider women who've previously had successful live births as the most optimal mating partner - despite that being the strongest indicator of fertility in women (which is why most legit surrogacy agencies require it of women who want to be surragotes).
and what's the reason that people find members of the opposite sex at the age where they just so happen to be fertile more attractive than members of the opposite sex that are too old or too young to be fertile? Because we evolved to be more attracted to human beings that are fertile or show signs that they are fertile than human beings that are not fertile because you can only reproduce with fertile human beings so being more attracted to fertile human beings than infertile human beings is a successful evolutionary strategy and so genes causing that behaviour spread through the population.
If you really think the way I asked the question caused the AI answer to be completely different from reality you could rewrite the prompt as something like :
"what are the strongest pieces of statistical evidence and proxy indicators that answer the question of whether on average people are indifferent over whether a partner or potential partner is infertile or fertile , and if on average there is a preference which way is it (other things being equal)? provide and link to sources"
the answer is basically exactly the same
Here:
https://chatgpt.com/share/6965998f-07c8-8012-9a29-420a8d160605
the two things you bring up in the your second paragraph are easily explained and neutralised and do not outweigh the much stronger evidence summarised by LLMs.
it's unsurprising and insignificant that cultures do not have norms or traditions of checking for infertility before marriage because it's usually impossible to check for infertility before marriage unless that person has an obvious injury or a trackrecord of having and failing to have children.
However it's not unusual in the modern day all over the world when it is known that a person is infertile (e.g. from a known injury or disease requiring removal of reproductive organs) for that person to report greatly reduced success on the marriage market. This is called infertility stigma and is well documented.
And yes having given birth before is the best way to guarantee someone is not infertile, however if someone has already given birth that has downsides because:
-it means their time and energy as a mother will be divided between looking after another man's kid or kids and looking after your kids and so they might want to have less kids with you than if you chose a similar woman who had no prior kids
-it means they're a non-virgin which increases the chance they might cheat on you which increases the chance that you could be genetically cuckolded and raise another man's kids that you believe to be your own ( this is true, look it up)
-it means you'll likely have to provide resources raising another man's child instead of using all your resources to maximise the chances of your own children's success
So these things all make it rational for a man who values fertility not to consider single motherhood to be unqualified, wholly attractive thing in a potential mate, so the fact that men don't consider single motherhood to be wholly desirable is totally consistent with the idea that men and people in general value fertility in partners and potential partners.