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.

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" without always having kids.

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

> The cause of silphium's supposed extinction is not entirely known but numerous factors are suggested.

> 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?

The Bible and plenty similarly old texts refers to marriage of such young women to usually older men, but even Romeo and Juliet is about 14 years olds.

Biological fertility as a baseline only slightly modified by social norms seems to be a good guess.

> Romeo and Juliet is about 14

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

Romeo and Juliet is fictional.

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.

I just mentioned it as a much later example for early marriages, but my other example(s) wasn’t refuted.

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.

The only "other example(s)" I could find from you was "The Bible". I (respectfully) avoided questioning it.

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.

bible is also fiction. I would agree with you but just to add that the bible is the same thing.

Within the time-span of the study, I would argue both the Bible and Romeo and Juliet are effectively modern/contemporary events.

Religious norms? Before 2013 age of consent in Vatican was 12.

That was my thought too; but if we average over a woman’s childbearing lifespan it makes more sense.

Those numbers aren't constant or the same for every group of people. There are genetic pools where girls reach puberty earlier than that.

Ex: https://www.nature.com/articles/ncomms8672

The linked paper doesn't obviously support the claim you're making here. Maybe I've missed something?

"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."

I would hazard that they are accounted for. People had very many children, only some children survived, some of those reproduced again, I would also guess that the mothers who would die during pregnancy or during childbirth would encounter that at one of the earlier in life pregnancies, and no longer be contributing to the average. I could see all that together supporting the average age of 23.

Also, today at least, miscarriages are relatively elevated in very young mothers, then decrease, and then increase again. IIRC, the lowest rates of miscarriage are in the early 20 to mid 20s or something like that.

It would be intersting to see what the average value is for primate species. When a female is able to conceive does it happen asap?

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?

Are female hunter-gatherers even sexually mature by 12-15?

Sexually mature? Definitely not. Able to procreate? That depends on nutrition, probably not, only a few years later (15-17).

Sexual maturity means that an organism as reached the capability of to reproduce.

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.

Having menarche and having the capability to bring a child to term are different. Pregnancies at early age have a higher rate of miscarriage. It seems there is a question of definition of sexual maturity - for me it is the age of reliably giving birth, for you the capability of getting pregnant. I am fine with either as long as it is clear what we use.

And nutrition depends on whether they have someone to feed them.