Figuring out that sex = reproduction

Not sure if this is more of a “great debate” but I’m not looking for a debate so I’ll ask this here first. I hope some anthropologist may be able to provide some insight on this question, if only the leading theories.

I’m wondering how, and approximately when, humans figured out that sexual intercourse leads to reproduction. With the 9 month gestation period there is a long delay between cause and effect. Plus, not every act of sexual intercourse leads to a pregnancy/birth. Those two factors always make discovering the causal link between A and B difficult. Let alone proving it.

Surely the compulsion to have sex is instinctual. But I’m interested in when and how humans gained the knowledge of the causal connection between the act of having sex and reproduction. And that knowledge is certainly not an ingrained instinct (hence the “birds and bees” talk parents have with their kids who probably believe babies come from storks up until said discussion). This knowledge is clearly learned, not instinctual.

I think it’s probably safe to assume humans knew this causal connection long before the point we began domesticating animals, keeping and breeding them so I don’t think “watching other animals” is a good answer (plus same issues with gestation period, etc).

“Penis goes into hole, and sometimes many moons later baby comes out of hole” is the only bit of relevant information they’d have had. I don’t think that’s close to enough info to figure it out… maybe enough info for a few smart early humans to come up with the “sex = reproduction” theory. But I’d think for most of human history that pregnancies were considered random acts, magical gifts from the gods, etc.

Anyway, I realize there’s probably not a specific answer to this question. But what are the leading theories among anthropologists as to how (and approximately when) humans made the connection between sexual intercourse and the babies that result? It’s common knowledge we all take for granted, but with the long delay between cause and effect, zero scientific understanding of the world, and less than 1:1 correlation between intercourse and pregnancy/birth, it actually amazes me that humans figured this out in pre-biblical times. Actually, it amazes me we figured it out before the 1700s.

Well you came to a good place to ask. I can’t speak on the topic, but Cecil took a stab at your question many years ago. Hope this helps a little bit.

I think we (this forum) may have had a discussion on this topic years ago but I can’t find the link at the moment.

For the record I did try to search to see if this had been discussed before, but I didn’t find anything.

Thanks for that link, it is pretty old but you’re right, Cecil did take a stab at this very question.
Any newer info/theories since 1990?

Not a lot of info there, but one thing Cecil says is we probably figured it out after domesticating animals and watching them, but that sounds sketchy to me (as I said in my OP). Seems you’d have known about reproduction before bothering to keep and domesticate animals. Otherwise why keep them and take the time and trouble to domesticate them? You keep them so they reproduce, so you have a renewable supply. No point in keeping animals if you don’t know how they reproduce. Without that knowledge it seems far more efficient to just hunt them as needed.

kaltkalt, I managed to find two previous threads on this question. Special thanks to pravnik for linking to one of the threads. More content in these, and they were 2006 and 2009, respectively.

It’s certainly possible to know THAT they reproduce, without knowing HOW they reproduce. So the animal explanation is valid.

There’s also the fact that, in both animals and humans, when looking at a female’s first sexual experience, though pregnancy doesn’t always result from it . . . it never precedes it.

I would like to add that the amount of time between sex and the realization that one is pregnant might me a lot less than 9 months. It isn’t too hard to imagine that pre-historic people probably figured out the signs of pregnancy and realized that they were going to (hopefully) give birth in the next few months. So the time between cause and effect is not necessarily 9 months. I think once the female realizes she missed her period she will know from watching other women go through something similar that she is probably pregnant and maybe that unforgettable night with Org was the cause.

OTOH this still puts the time between cause and effect to be at least one month and likely longer.

We don’t know, and probably never will, but I doubt Cecil is right. I suspect that humans were smart enough to figure out sex = babies long before 10,000 years ago. They would have had ample opportunity to observe this in animals and humans.d

It would not surprise me if they thought, as was common even in the Middle Ages, that men plant a seed in a woman, and that the woman had no material input into the baby.

Automagic: That’s a best-case scenario considering a very gossipy community with a complex spoken language. And even then I think merely missing a period wouldn’t itself make a connection with anything. I do think early humans would figure out the correlation between women suddenly getting really fat and having a baby pop out at their fattest. So maybe the question eventually becomes how did they figure out the correlation between sex and women quickly getting big bulging bellies. But it would still take several months before the “pregnant cavewoman” really began to show. And still not every act of sexual intercourse leads to a pregnancy… I’d think overall the minority do (i’m sure the numbers on the chances of getting pregnant at any random point in a woman’s period from one random act of sex with one man can be found somewhere and I bet it’s less than 50%). How many of these people even had primitive calendars (I know the Mayans did, world ending less than a year from now and all) and would routinely be counting days?

Thus the time between cause and effect is still quite a while, and cause doesn’t result in effect every time. The longer the time between cause and effect, and the less frequently the cause results in the effect are the two factors that make discovering cause and effect most difficult.

Long, long before humans domesticated animals, while humans were still hunter-gatherers, they would have been well aware of the mating seasons of the animals that they hunt. And that the mating season lead to the birthing season.

The season of the “rut” when herd animals gather and the males compete for the right to mate makes these prey animals much easier to hunt. Normally careful males make poor decisions, are active even in the day time, are easier to find, and may run themselves to exhaustion. The females are spooked and in heat, herding together for protection.

The modern deer hunter knows all about the rut and uses it to his/her advantage, and so did the ancient hunters. Even non-human predators follow prey during the mating and birthing seasons.

Humans figured out the connection between the mating season and birthing season because this knowledge had survival value.

The argument that sex infrequently results in pregnancy doesn’t really hold up. Cave women (probably) weren’t having occasional sex at long intervals. They probably started having sex, kept having sex, and then started having babies. She (probably) never had reason to think, ‘I’ve had sex six times and only been pregnant once’, because she was already pregnant three or four of those times.

Furthermore, the interval between starting to have sex and knowing she was pregnant was (probably) a lot less than nine months; unless she lived without any other women around, she probably knew in about two weeks.

Dallas: I’m sure they’d know certain times were better for hunting than others… but I doubt they knew it had to do with mating season. The way humans think, they probably figured it had to do with the moon, the stars, or because they did the right dance and pleased the hunting gods. Human history - even today - is practically based on erroneous links between cause and effect. Look at how many people still believe in stuff like astrology and prayer. We lit a bonfire and the hunting was good this day… surely that must be why. To even think they’d be aware of mating, let alone mating seasons is extremely unlikely IMHO.
j666: the more frequent sex was, and the more partners a cave woman had, would make cause and effect even less obvious. Say the typical cave woman gets clonked over the head with a bone and raped once or twice a day on average. Eventually she’ll start to grow a big belly and a few months later give birth. Why would that possibly make the connection between sex and birth more obvious? I think it makes it much less obvious. Sex would be a regular, daily event. Why would they conclude sex causes birth any more than concluding that eating causes birth? I bet eating the right fruits or meats - eating the still beating heart of the mammoth - is a much more likely thing early humans would conclude causes their women to get fat and pop out a baby-human. Food goes in, baby comes out. Just as logical as sex, and probably just as frequent.

If Cecil’s column is right (unfortunately it’s one of the least informative one I’ve ever read) there may be some tribes of aborigines who still today do not know what causes pregnancy/birth.

Not at all logical. People eat things all their lives. And men eat things too. A woman eats fruit and meat before she starts her menstrual cycle and does not get pregnant. Once the menstrual cycle beings she can get pregnant. It doesn’t take a genius to figure out that these events are related, especially when they’re all related to the vagina. In very frank terms - blood comes out, sperm goes in, baby comes out. (obviously not all at the same time :o but cause and effect, like.)

I remember figuring this out (in very vague terms) before I actually had sex ed, so I don’t imagine it was difficult for primitive humans.

I recall an article a year or two ao about the Pill, cervical cancer, etc. The anthropologist had tracked a small African village that had a hut the women went to when “unclean”. Her observation was that unlike western women, a poor subsitnece tribe’s women had about half the periods in a lifetime. Periods started much later because of poorer nutrition and ended earlier. The monthly cycle was not as guaranteed or regular, and many early miscarriages also figured into the mix.

The article’s point was that in designing the Pill to accomodate the Vatican’s bizzare beliefs (the developer of the first Pill was a devout catholic!) western women have regular periods from 11 or 12 well into their 40’s and only one or two children typically. The suggestion was that this frequent shedding of the uterus lining may contribute to higher rates of cancer.

To get back to the OP, if periods started much later than primitive marriage, deflowering (or whatever) age, if periods are irregular, if early miscarriages are frequent, and (since we are discussing cavemen) sex is frequent, then the link between sex and pregnancy may not have been as obvious as we think it should be.

However, when the point is hammered home (so to speak) that the baby looks like whoever was the woman’s most frequent flyer (so to speak) then it probably does not take a genius to say “the more you do this to her, the more likely she will have a child that looks like you”. Add to that the male instinct to prevent others from boinking their harem, and we are well on the way the correct assumption even if the exact mechanism of fertilization is not clearly understood.

I’m sure they noticed that women who were virgins rarely had babies.

The popular science magazines have been running interesting articles about memory, and whether animals have memory and if so what that implies. Results are early and inconclusive, of course, but my reading of them leads me to believe that most animals don’t have a conception of time as cause and effect the way humans do. They can be conditioned to respond to a trigger but that’s not the same as human memory of events in the past having indirect meaning on our current lives.

If so, there had to be a time when Homo either did not have or was just evolving a memory that would link past events to current ones. I don’t know when that happened, or if that was something that occurred during the span of Homo Sapiens, like those other major events that seem to place creativity and language at a specific time.

Once humans have this type of memory, though, I’d think the connection between sex and reproduction would soon follow. That could make it very old.

How often did that happen? The only unused women would be those past reproduction age and into the great-grandma stage…

A closer question would be - what came first, the understanding sex=babies or the social construct of marriage (or, as it was called in those days, “I own these women, hands off or I have the right to kill you…”)

Cecil Adams has a sexually mature brother who does not find a connection between sex and pregnancy! :eek:

Most tribal societies have some version of an initiation rite to introduce girls into womanhood, just as they have rites that introduce boys into manhood. You can ask when societies became advanced enough to create these rites and whether they thought that the rites themselves made pregnancy possible. But thinking that human groups wouldn’t recognize the status of virgins is doubtful at best.

If humans are human enough to have memory, then they probably are human enough not to rape women at the first physical opportunity. Nor is “ownership” of women a universal in tribal cultures. Women have a full range of statuses.