What mating system did prehistoric humans use? In gorillas dominant males have harems of about 5 females that they defend from other males. Chimp troops are more of a sexual free-for-all in which males and females mate promiscuously with each other.


Gorilla mating system. Silverbacks defend harems from outsider males.


Chimp mating system. Males and females in a troop mate promiscuously and don’t form exclusive long-term relationships.

Although people can sometimes be promiscuous or have short-term relationships the primary mating system used in our species is long-term relationships or marriages. In all societies men keep wives that they guard from other men. In primitive foraging societies it’s common for higher status men to have more than one wife. The headman in a tribe, for instance, could have 5 wives. I’m simplifying a bit but the basic algorithm men have evolved to follow is to acquire females, hold on to them, copulate with them regularly, and try to get as many offspring from them as long as possible over the long-term.


Human mating system. Men keep wives and guard them from other men in the community. Due to some men having more than one wife a certain number of men remain single.

If keeping wives was the mating system prehistoric men used then what would have been the best age of female for them to acquire? What they needed were females who could be expected to give them the most offspring over the long-term. A woman past menopause would be no good since she has no more fertile years remaining. A younger woman about 30 half way through her reproductive lifespan would be better as she has half her fertile years remaining and will be capable of giving a man some offspring. The best females of all would be those who haven’t started reproducing yet and still have all their fertile years ahead of them. If the typical age prehistoric girls got pregnant for the first time was about 17 this age would have been the deadline by which a man needed to acquire females in order to get as many offspring from them as possible. From the age of about 17 prehistoric females would have had progressively fewer reproductive years remaining and the amount of offspring they could give a man over the long-term would go down.

Very young girls, say 5 year olds, would have all their reproductive years ahead of them but the obvious problem with wives this young is that a man would have to wait over a decade before they would start giving him offspring. It would be better to get girls closer to the beginning of their reproductive lifespan (about 17) but how close exactly?

We can start out considering an idealised, simplified population in which every girl starts reproducing at exactly 17 and there’s no other males a man has to compete against. In this simplified model the best age for a man to acquire a wife would be at exactly 17 so she would start reproducing and giving him offspring immediately.


In an idealised model the best age to acquire a female is exactly at the beginning of her reproductive lifespan. Age of last reproduction is not that important in this discussion and has been set at 45.

This model is obviously very unrealistic and too idealised. In a real population girls start reproducing at different ages, some a bit before 17, some a bit after. A man also has to claim a female before any other man in the tribe does. Considering these things it’s best for a man to err on the side of caution and go for females a few years under 17. A simple analogy will make this clearer.

Imagine there’s a species of cow that lives on a cliff top and feeds off the grass that grows there. The grass is more and more nutritious the closer to the edge of the cliff so that the very most nutritious grass is right along the edge. We wouldn’t expect the cows to evolve to feed off the grass right on the edge, for obvious reasons. Instead we’d expect them to eat the slightly less nutritious grass a little way back from the edge because the penalty of going over the edge is far greater than the penalty of stopping a little bit short.

The edge of the cliff of course stands for the beginning of a girl’s reproductive lifespan. The beginning of a girl’s reproductive lifespan is more of a deadline more than a target. By acquiring a girl a few years before she starts reproducing a man pays the penalty of having to wait a few years before he starts getting offspring from her but the penalty of losing her to another man or acquiring after she starts using up her reproductive years would be far greater.


In a real population the boundary is fuzzy. It’s best to err on the side of caution and go for girls a bit before the average age of first pregnancy.

The best girls to acquire as wives wouldn’t be those at the age of 17 itself but instead those approaching 17 or about 12-16. We can see now the biological reason for the popularity of the jailbait category. These are girls that would have been approaching the beginning of their reproductive lifespans in prehistoric times. They would have been ready to have sex but hadn’t yet got pregnant and would be capable of giving a man the most offspring over the long-term.

Why do adolescent girls have boobs?

If you ever see some footage of primitive tribes that don’t wear clothes one of the first things you notice is that the adult women have horrible saggy boobs. This is what adult boobs are supposed to look like. A girl’s boobs are at their pertest and most attractive in her adolescent years before she starts reproducing. Once she starts having babies and breastfeeding, usually by the late teens, her boobs quickly lose their adolescent pertness and become less attractive. The pert boobs of the average nulliparous (hasn’t had a baby yet) 14yo girl are much more attractive than the drooping boobs of the average 20yo who’s had a baby or two.

The 14yo girl’s boobs are an honest advertisement of nulliparity. They’re more of an advertisement of future fertility than current fertility. They’re a signal saying “I’m approaching reproductive age and ready to start mating. I haven’t started reproducing yet and have all my fertile years remaining. Acquire me at this age and you can have all my fertile years to yourself and I’ll start giving you offspring soon.” Men’s preference for pert adolescent boobs has co-evolved with this signalling.

Another honest advertisement of nulliparity is a tight midriff that hasn’t been stretched by pregnancy. This is presumably the reason adolescent girls like to wear short tops that show off their stomachs.

Misguided arguments against the adaptiveness of adolescentophilia

The argument often used to try and prove that adolescentophilia would have been maladaptive is that the adolescent years are not the best age for a girl to start reproducing. Adolescent mothers have higher rates of pregnancy complications and girls who start reproducing before the age of 16 have fewer offspring overall than girls who start at 16 or later. Here’s an example of this argument being made in the literature by Blanchard:

There exists an entire literature demonstrating that pregnancies during puberty are highly risky and often fatal to both mother and child. The most direct evidence showing that early pregnancy holds no reproductive advantage in evolution is the measurement of numbers of offspring within pre-industrial societies. In the American Journal of Physical Anthropology, Kramer (2008) analyzed the effects of early sexual maturity in a savannah-dwelling society of subsistence foragers, called the Pumé. The crosssectional data from the women showed that menarche began at age 12.75 years, on average. Women who gave birth before age 14 had an infant mortality rate of 55%, compared with a rate of 6.7% whose first birth was after age 16. Finally, and most relevantly, Kramer calculated the total fertility for Pumé females who initiate childbearing at young, average, or late ages, and found that the number of surviving children born to women who became pregnant while young was significantly less than that for the other two groups.

The genes most likely to spread are those most likely to lead to subsequent generations. The children born to mothers impregnated during puberty, however, show only disadvantages (e.g., Haiek & Lederman, 1989; Olausson, Cnattingius, & Haglund, 1999). A New England Journal of Medicine study analyzed a sample of more than 170,000 births (Fraser, 1995). Infants born to mothers aged 13–17 showed each of lower birth weight, greater rates of premature infants, and greater rates of small-for-gestational-age births relative to infants born to mothers aged 18–19, or to mothers aged 20–24, the age range associated with the fewest adverse outcomes. The study controlled for the socioeconomic and demographic differences among these age groups, allowing it to conclude that the poor outcomes were due to the biological unpreparedness of the mothers’ bodies, which are again older than the pertinent age range of 11–14.

Also arguing against evolutionary adaptiveness is that, even when a pubescent child does become pregnant, the pregnancy is a relatively dangerous one, both for the health of the infant and the health of the mother. Pregnancies of girls age 14 and younger are five times more likely to result in the death of the mother than are pregnancies at ages 20–24 (Mayor, 2004). The risk of neonatal death among the infants is 3–4 times higher among children from mothers age 15 or younger than from mothers age 23–29 (Phipps, Blume, & DeMonner, 2002). (Because that study used a cap of age 15 instead of 14, one would reasonably hypothesize that using a cap of 14 would show a still more deleterious outcome.)

Where this line of argument goes wrong is that the issue isn’t whether the adolescent years is the best age for a girl to become a MOTHER but rather whether it’s the best age for her to become a WIFE. If a man acquired a 12 or 14yo wife she wouldn’t typically start reproducing at that age but rather several years later at about 17. That’s the whole point. In order to monopolise a girl’s reproductive lifespan and get as many offspring from her as possible a man needed to acquire her some time before she started reproducing. There would be rare cases where a man’s wife got pregnant at 12 or 14 and died in childbirth or something but this isn’t what would TYPICALLY happen. The few cases of early pregnancy wouldn’t have made it maladaptive for men to form sexual relationships with adolescent girls anymore than the rare cases of people choking to death eating steaks would have made it maladaptive to eat meat.

What we want to know is the reproductive success of the males as a function of the age of the females they pursue and acquire: are men who acquire 14yo wives more or less reproductively successful than men who acquire 20yo wives etc? What those statistics show is the reproductive success of the females as a function of the age at which they start reproducing. He’s got the wrong statistics and it’s really fucking laughable. The statistics only show that it would be maladaptive for girls to start reproducing in their pubescent years. They tell us nothing about the reproductive success of men who acquired pubescent girls as wives.

In prehistoric societies the typical 20yo would have already had a baby or two and started using up her fertile years. The typical 14yo would still be nulliparous and have all her fertile years ahead of her. Men who acquired 14yo wives would have got more offspring from them than men who acquired 20yo wives. It’s not complicated.

Girls under 12 can be wives too

If girls about 12-16 were the best to acquire as wives what about girls a bit younger say 9? A 9yo wife wouldn’t be ideal since she wouldn’t reach reproductive age for about 8 years but it can still work. Humans have long lifespans and as long as he’s not too old a man can afford to wait. Even if he does die before she reaches reproductive age he can still benefit through inclusive fitness since widows in primitive societies are usually passed on to their dead husband’s brothers or other close male relatives.

In primitive societies it’s quite common for men to marry girls of this age so although it’s sub-optimal the strategy definitely does work. We must expect men to have evolved adaptations for acquiring girls of this age such as finding them physically attractive and being susceptible to falling in love with them but to also be averse to having intercourse with them since they’re not physically ready for it.

As we go younger and younger there will be a point at which girls are too far away from the beginning of their reproductive lifespans and the probability of them surviving to reproductive age is too low for it to be worthwhile for a man to chase after them, assuming older females are available too. I estimate of this age to be about 7 since it’s uncommon for men in primitive societies to marry girls under the age of about 7.

Females in prehistoric societies

Ages 0-6, infants and younger juveniles:
Girls this age are a long way from reproductive age and it’s generally not worthwhile for a man to invest much effort in acquiring them as wives. Mortality is high and there’s a good chance a girl this age won’t survive to reproductive age. If a girl this age is offered to man as a gift he might as well take her but it’s not worth investing effort in chasing after girls this age. It’s generally best for a man to ignore girls this young. There’s little competition between the males for girls this age.

Ages 7-11, older juveniles:
These girls are closer to reproductive age and it’s now worthwhile for a man to invest effort in trying to acquire them as wives. They’re past the younger juvenile stage and the chance of them surviving to reproductive age is over 90%. Competition for girls this age is rising as they approach reproductive age. Men often fall in love with girls this age and get married to them but won’t usually have intercourse with them until adolescence. Similarly, girls this age may be abducted by raiders from other tribes to be kept as wives but they won’t usually have intercourse with (or rape) them this young.

Ages 12-16, adolescents:
Now the heat’s really on. The girls are on the verge of reproductive age and approaching the deadline. They are ready to mate with but haven’t yet got pregnant. Competition for them is at its fiercest since the man who wins a girl at this age can have all her future fertile years to himself and won’t have to wait long before she starts reproducing. Fights often break out over them and sometimes result in death. At this age they’re at their greatest danger of being kidnapped by raiders. Their pristine, perky adolescent boobs and bodies make them stand out from the juvenile girls and the adult women whose bodies show signs of prior pregnancies such as drooping boobs and stretchmarks. Their faces and bodies have an adolescent sparkle that catches men’s attention and incites men to chase after and compete for them. Their vaginas are not yet damaged by childbirth. Girls this age without husbands or male protectors are routinely pushed around, sexually harassed, and raped by the men in the tribe. I’m not just saying this to be shocking, this is how savage ancestral humans probably were.

Age 17 onward, adults:
Competition for girls now goes into decline. Girls this age have now started reproducing and are biologically adults. From this age onward the number fertile years women have remaining goes into decline. This decline is reflected in declining physical appearance. Their boobs get saggier with every pregnancy, their stomachs accumulate stretchmarks, their waists go flabby, their faces grow duller every year, and they develop cellulite and get fatter. Bear in mind that these people are near-naked and everything is on display. Women in modern societies can cover themselves up and wear bras that give the illusion their boobs are still pert and artificially recreate their adolescent attractiveness.

By age 30:
Most women by now have had at least three pregnancies and it shows. Their boobs are horribly saggy, their waists have lost their feminine shape and their vaginas don’t look too good after giving birth multiple times. They’re now considered old women and the men aren’t that interested in taking them on as a wives. Their own husbands continue having sex with them more out of a matter of routine than sexual attraction. Their husbands remember how attractive they were as adolescents before they had children and would like to take on additional adolescent or juvenile wives.

Anticipated questions and comments

-I’ve read that people in primitive populations are serially monogamous rather than having long-term relationships. People form couples, stay together for a few years to raise a baby or two, then split up and find someone else.

Kind of but that’s not the best way of looking at it. What’s really happening is a series of failed long-term relationships than deliberate serial monogamy. In species that practice serial monogamy the males usually prefer females who have already had offspring and have practice raising young. If you’re going to pair up with someone for a season and raise a kid together you want someone who’s done it before and knows what they’re doing. The males in our species appear to have evolved to prefer the females best for long-term relationships: nulliparous females who are capable of producing the most offspring over the long-term. These relationships don’t always endure out but some of them do and so men who preferred to acquire young nulliparous females would on average have had the highest reproductive success.

-Haven’t men evolved to just to run around and have as many one-night-stands as possible to spread their seed rather than keep wives?

The biological function of men’s desire to have many partners is probably less about motivating them to “spread their seed” and more about motivating them to try to acquire as many females as possible and build harems. The fact that sexual attraction peaks for nulliparous teens rather than parous women in their 20s with the highest fertility I think pretty much proves this. We evolved in small communities where men didn’t often meet new women they could have one-night-stands with and sleeping around within their own community could easily get them killed by possessive husbands.

-I get that girls wouldn’t typically start reproducing until the mid to late teens but even this isn’t the best age to have a baby and is associated with adverse outcomes. The best age is about 20-24.

The best age to have an individual pregnancy is about 20-24 but the the best age for a girl to start reproducing in order to produce the most offspring overall and leave behind the most descendants seems to be about the mid to late teens. The earlier a girl starts reproducing the more offspring she can have altogether but only to a point. If she starts too young, say 12, the greater risks associated with becoming a mother at that age will outweigh the benefits of the longer reproductive lifespan. At some age below the early 20s there must be a point at which the benefits of the longer reproductive lifespan are in balance with the higher risks of pregnancy at that age and this seems to be the mid to late teens.

-So if this is right and the best age of females for men go for were those just prior the beginning of their reproductive lifespans, do we see the same thing in any other animals? It can’t be unique to us.

You see a similar thing Hamadryas baboons. The males build harems and keep “wives” they guard from other males in the community similarly to men in primitive foraging societies. The females typically start reproducing about 6 and are recruited into harems a bit before that as adolescents or older juveniles. The human equivalent would be girls 15, 12 or 9 kind of age. Similarly to our species the females can be recruited from within a male’s own community or kidnapped from neighbouring communities.

-What evidence is there that adolescentophilia is normal for men?

Due to taboos over minor attraction it hasn’t been studied much and most of the sexologists who do research this stuff don’t seem to be objective. But here’s some evidence I’ve been able to gather myself off the internet.

1. Search statistics show that girls about 14 are the most searched for:


From “One Billion Wicked Thoughts” by Ogi Ogas and Sai Gaddam.

2. The frequencies of age related porn search terms are what biology predicts. Teens and preteens are most popular.


Also from “One Billion Wicked Thoughts” by Ogi Ogas and Sai Gaddam.

3. In this study men rated female faces about 13 years old the most attractive: Other studies show similar results. It’s known that facial attractiveness plays a much bigger role in determining overall attractiveness than bodily attractiveness, so these studies are strong evidence that men generally find adolescent girls the most desirable.

4. The BMI men find the most attractive is about 17-20 which is the typical BMI for girls about 13. Women naturally get fatter when they start having babies so a low BMI is another sign of nulliparity and youth.


Men rate the typical BMI for girls about 13 the most attractive.

5. “Catch a Predator” type shows usually use girls about 14 as bait because that’s what draws the most men.

6. The fact that the most popular age category on legal porn sites is the legal minimum (18-19) strongly suggests that what the market wants is girls under that age. If there were no legal restrictions the most popular age for girls in the porn industry would be likely to be a few years younger.

7. The vulvas that get posted in “Post up the best looking pussies” threads on porn sites always look like they could belong to girls about 12 or 14. They are nice and neat with little or no pubic hair and have a virginal, slightly immature look about them. (A vulva that’s tight and fresh looking is a sign that the girl it belongs to hasn’t started reproducing yet and still has all of her fertile years ahead of her).

8. The porn site allows users to create their own groups that other people can view and post in. Before they got strict these were the top ten groups:

1. Young
2. Stickam
3. Incest
4. Jailbait
5. Daughters
6. Teen
7. deutsche teens
8. little puff nipples and hairless pussys
9. School Girls
10. Very Cute Only

The “Young” group was mostly filled with girls about 14. If there were no legal restrictions that’s what the porn industry would be using.

9. Similarly, before reddit got strict one of the most popular subreddits was /r/jailbait which was devoted to pictures and videos of girls about 12-16. This subreddit was so popular it was the first thing that came up in google when people searched for “reddit”.

10. Crime statistics show that girls are at the greatest risk of being sexually assaulted or raped at the age of about 12-17.

Canada sex crime

Canadian sex crime statistics.

FBI sex crime

FBI sex crime statistics.

11. Anthropological statistics show girls in hunter-gatherer societies are typically married off around the age of 14.


Age girls in hunter-gatherer societies are married off.

12. Warfare, genocide, conquest, and “woman theft” appear to have been common among prehistoric tribes and ancient societies. Archaeologists often find that the skeletons of adolescent girls are under-represented in the graves of slaughtered tribes. Presumably they were spared death and kept as wives by the attacking tribes.

-Have you heard of the concept of reproductive value in mathematical biology? You’re basically arguing that men have evolved to find girls of high reproductive value most attractive.

Yes, men have evolved to find high RV + nulliparity highly attractive. RV is basically a measure of the amount of offspring a female can be expected to have over the remainder of her life. This increases with age up until first reproduction, as the probability of her dying before she starts reproducing decreases, and then goes into decline as she uses up her fertile years. The best age to acquire a female as a wife is just before she peaks in RV. See diagram below.

rv graph

Graph of female reproductive value with explanations.