I agree, female breasts should be viewed through evolutionary theory with hesitation. What does the research say on how the changes in diet/nutrition over the past few centuries affected the female breast size?
Well, fatter women get bigger breasts. With a few exceptions, breast size is very sensitive to weight gain and weight loss. My source for that claim is not research but just observation: Women complain that their breasts get smaller when they diet.
Wouldn't one reason to mate with a well-fed, breastfeeding woman be that she is likely to already have a man caring for her and her children? If you mate with her, then you can get him to invest in your child for you.
Hm. That was a difficult one. You mean, pre-human women fooled high-status males they were already provided for through looking as they were breastfeeding? And then when males found out the females were actually single they felt obliged to protect and provide for them anyway?
The important question is how male appreciation gave an advantage to women. If women evolved to have breasts, that must have been because having breasts was beneficial for women themselves.
Great point. I think the story I have in mind is that there are lots of "normal" males and a few "exceptional" males. The exceptional males are genetically desirable mates to all the females, so much so that females are willing to mate with them even if they provide little or no support. But they are only willing to mate with normal males if they also protect and provide for the children. So you could end up with an equilibrium where females enter into pair-bond relationships with normal males and have children with them. A small number of exceptional males basically sneak around surreptitiously mating with all the females as well and mixing their offspring in among the offspring of the normal males. In this way, the few exceptional males could end up being vastly overrepresented genetically in the next generation.
If these exceptional males prefer breasts, then a preference for breasts will be selected for. If females with breasts are more likely to attract exceptional males, and the children of exceptional males are more likely to survive childhood, then having breasts will be selected for. Since many of the normal males are actually children of an exceptional male father, they too are likely to prefer breasts, which just reinforces the cycle.
So why might exceptional males prefer breasts in the first place? Well, it's a sign that the female is well-fed and breastfeeding (implying she is fertile, capable of surviving childbirth, and experienced raising children). Moreover, being well-fed and breastfeeding are a good sign that she is in a pair-bond with a normal male who is protecting her and supporting her children. This makes her an ideal mate for an exceptional male because it means his offspring will be cared for by a competent mother and be well protected and provided for by her pair-bond mate.
re: . That way, having sex with a woman because early pregnancy gave her ballooning breasts seems like a very bad idea indeed.
Why should only investing in your own children be an evolutionary advantage?
Consider two groups of closely related individuals. In one group the males only invest in children who are known to be theirs. In the other group, the males invest in all of the kids in the group. If more children are successfully reared in the second group, then this is a winning strategy ... 'if we all work together we can raise more kids'.
From a woman's point of view, having every male member of the group somewhat invested in raising the children you have already made the huge investment in bringing to term is a major win.
On some level that is certainly right. In our society men invest in each other's children through paying taxes. And it has been a comparatively successful society (although it is not demographically successful right now).
Still, I don't think we will ever escape selection between individual males (and females). And in that selection those who invest in their own children have an advantage.
It's not the financial investment I am most interested in here, but the time. In Sweden, despite having plenty of divorced people and children who are growing up in two households and the like, we don't have a society of men who leave the children and child-raising to the women, while they sit around in all-male groups, drinking and smoking whatever intoxicants and stimulants are permitted by their society and perriodically killing other men and groups of other men who live in similar ways. This 'men are for drunkenness and war/defence' pattern shows up again, and again, and again when anthropologists study people, so it seems to be one that people need to take particular care to avoid in their societies.
I am reading Lars Trägårdh, “Statist Individualism: The Swedish Theory of Love and Its Lutheran Imprint,” in Between the State and the Eucharist: Free Church Theology in Conversation with William T. Kavanaugh, Joel Halldorf and Fredrik Wenell (eds.) (Eugene, OR: Wipf and Stock Publishers, 2014) right now. Facinating stuff, for me, in trying to figure out how we got the Swedish society and not something else.
However, back to the thought experiement about boobs.
Men who have _other men_ invest in their children have an advantage. Consider a society where there is perfect agreement among the females as to who is the most genetically fit male individual. In terms of genes, that one is the one that _everybody_ wants to breed with, to produce the very best outcome in the next generation, children who are 50% your genes (which you are stuck with, in your children, no matter whom you breed with) and 50% the acknowledged best male package of genes out there.
Having not invented monogamy, or anything close to it, let us say that all the women get pregnant by SuperGenePack. If SuperGenePack is the only male doing any investment in the children, then the group will raise many fewer children than groups where the men are all invested in children. Raising SuperGenePack's offspring may be a suboptimal strategy for the males who aren't SuperGenePack, but it's great for SuperGenePack. And if SuperGenePack carries a package of genes for 'my sons like big boobs' and another for 'my daughter has big boobs' these two new packages will become defining traits of subsequent generations.
In the game of numbers, 'Who gets the most grandchildren?', the stakes for women and men are not the same. Men can get a wide range of outcomes, from 'no offspring' to 'every child is my child' for the next generation. Women will get, in population terms, a very narrow range of outcomes, one that is shared with every other woman, and is based on how many pregnancies you can fit into your reproductive lifespan. No matter how much a woman might wish to have 100 children, there just isn't enough time for that. But 100 grandchildren? That could happen. One of your children needs to be the SuperGenePack of his generation.
My hypothetical situation is unlikely to be stable. There is too much incentive for the men who aren't SuperGenePack to combine forces and subdue and force fertile women to have sex with them. But a society where each woman tries to grab one male for the raising of all of her children, most of whom will be his, but who sneaks off for a little adultery with SuperGenePack may be stable. For simplicity's sake, assume that all women have the same number of children in their lifetime. Also ssume for the experiment that every woman enters into a promised monogamous relationship with one man, but sneaks off exactly once for some sex with SuperGenePack. The adultery represents her one bet on producing the next generations' SuperGenePack. The rest of the time she is just producing the usual number of children for the next generation. This is what most of the males are doing as well, they are either producing the normal number of children for the next generation or that number -1, because they are raising one of SuperGenePack's kids in addition to their own.
SuperGenePack gets the best outcome -- he gets the normal number of children for the next generation out of his official mate, plus however so many children got conceived in his very many adulteries. His genes will prosper, albeit not as rapidly as the scenario where he sired the entire next generation.
"We don't have a society of men who leave the children and child-raising to the women, they sit around in all-male groups, drinking and smoking whatever intoxicants and stimulants are permitted by their society and periodically killing other men and groups of other men who live in similar ways."
That is entirely true. But isn't that partially an effect of contraception? Women refuse to have children with men whom they believe would engage in further mating effort instead of parenting effort. The result is that we don't have many children at all. Maybe women would be willing to have many more children if more men were willing to invest.
'Mean liking boobs' cannot be an effect of contraception because human men developed the attraction long before we had any contraception, beyond lactation. 'Men are only good for violence and sex, the rest of the time the lazy bums don't do anything' is a pattern than predates contraception as well. These days women who can afford nannies and other servants to take care of their children do not typically have more children than those who have to do their own raising, so I think it will take more than 'more income' and 'more male investment' to produce larger families. (Kristina Ozturk and her husband's plan to have via surrogacy 22 children in 19 months is very much the exception.) Convincing women that the world is not overpopulated and that it is therefore not selfish to have children seems to be one of the other things that is needed.
After reading over the article again and following through the comments, I think it's worth organizing a clear response to this idea.
If I read this correctly, Tove is saying humans are unusual: adult females have breasts regardless of pregnancy status. This appears to have been a sexually selected trait. What is the explanation? Tove considers and rejects five hypotheses:
1. Extra buttocks,
2. Fat stores,
3. Handicap,
4. Age Indication, and
5. Fertility.
I don't really think these five explanations truly deserves to go to the garbage dump of ideas at https://woodfromeden.substack.com/p/the-order-of-thoughts . Some are better than others, though. #4 doesn't make sense early on, and I never considered #3 even particularly reasonable for male traits. But #1, #2, and #5 have some merit. Clearly, breasts do echo buttocks. Clearly, breasts are fat stores which may be useful. And females with breasts were at least able to become pregnant at one time. But Tove advances a different explanation:
6. MILF hypothesis. "[A]pe males have a strong preference for females who have already given birth and have the experience to raise an infant successfully....One clear marker of female self-reliance is if she is both breastfeeding and fertile."
This isn't perfect. If it were, then I think we would expect nulliparous chimpanzee females to already show breast development. Still, it does seem reasonable to think that as more maternal investment was required in childrearing, at least some males may have pursued a successful strategy of pursuing lactating females for the reasons you cite. In a similar vein, I also want to mention one other thing that I think is going on:
7. Femininity hypothesis. Signals like smaller hands and feet, high voices, and smaller stature all confuse femininity and youth. Long, lustrous hair and dark lashes do slightly better to signal femininity, but full breasts on an otherwise slender individual signal femininity very cleanly.
I don't think that #7 is actually the explanation any more than #6, though. Mammary tissue may be effective at signalling feminine sex and the ability to raise an infant successfully, in more modern humans, hip girth is a cleaner signal of both things motherhood, which doesn't also signal depressed fertility, as swollen breasts do. So what's the solution?
What I actually think is this: In the beginning, ancestral humans weren't particularly attracted to breasts and didn't form pair bonds. However, they had some mental modules related to breasts that could be co-opted to promote pair bonding.
Early hominins were likely to be slightly interested in breasts because of the ideas mentioned previously: Breasts reminded ancestral males of buttocks, they were useful fat stores, they signaled healthy femininity, and proved that a female was an experienced breeder.
As evolution progressed, gestation times lengthened from around 227 towards 280 days ( https://pubmed.ncbi.nlm.nih.gov/13646623/ ), fetuses increased in weight from 4 towards 7 pounds, and the period of infant helplessness extended towards a full year. Throughout this process mothers became extremely vulnerable for a longer and longer period. Initially this time of vulnerability may have only a been a month or two, but in the later stages of evolution it corresponded to something like the onset of the third trimester all the way to the end of the child's first year after birth. During this period, mothers and their offspring required provisioning and protection to ensure the father passed on his genes. Thus it wasn't enough for males to mate and wander away; a successful male would mate and stay. The period of greatest vulnerability would likely be exactly the time when her breasts were largest: immediately after birth.
Male hominins were already slightly interested in breasts for the reasons cited earlier. And some were likely more interested than others. As maternal vulnerability increased, those males who became excited when their partners showed signs of pregnancy would stay. Male sexual attraction to the partner would provide an incentive to provision and protect the offspring. Breasts were an excellent signal to a male that he ought to be attracted to the female who has them - particularly if she showed signs of being his particular mate (by smiling, making eye contact, and so on). When the period of vulnerability ended, the breasts went away, and he lost interest.
Probably it was only most recently, in the later stages of evolution, that females would develop and maintain breasts outside of pregnancy. With the emergence of culture, children required training and guidance, and they did better if the father never really lost interest in their mother at all. This stage never really completed in modern humans; divorce rates today peak between the 4th and 8th year. But the breasts, and human male interest in them, are still there.
Call it 8. The Paternal Provisioning Hypothesis: Mommies and babies need dad around to make them apple pie.
I think there is a reasonable explanation why nulliparous chimpanzee females don't show breast development: Because being discriminated against doesn't hurt them very much. They don't need alpha sperm for their first child anyway. Being discriminated against is much worse for human females, who can realistically hope for some male investment.
In a subgroup to the chimpanzees, the bonobos, females actually did develop a costly defense against discrimination: Since males tended to discriminate against females that did not have swollen genitalia, bonobo females evolved genital swellings that last for 3 out of 4 weeks, instead of only 1 out of 4 weeks as in the common chimpanzee.
I think your theories make a lot of sense. Especially #8: It seems to be fairly common that men find pregnancy explicitly sexually arousing. #6 more or less needs #8 to be sustainable: #6 only explains how fat breasts once might have evolved. It doesn't explain why they didn't disappear again, despite being costly. It also doesn't explain why males didn't develop counterstrategies: Being maximally attracted to females who are six weeks pregnant carries some obvious risks. #8 explains why that risk was worth taking after all.
"Male sexuality is infamous for being superficial and stupid. But is it that stupid?"
Oh my goodness yes. Haven't you noticed how Pavlovian male sexual response is? A male full of prostate fluid is really just wandering around hoping to find an appropriate place to make a deposit. Whatever signal he's primed to respond to - the scent of musk, swollen genitals, a flicking of the tail feathers, a high frequency yowl, whatever - he'll respond.
Of course the great apes are decidedly visual in orientation, not only blessed with trichromatic vision but (in the hominins, at least) a highly sensitive link from visual stimuli to erotic response. I've heard that some people are so easily excited by the sight of hairless globular fatty tissue that they respond orgasmically to mere computer images, without the need for any fertile female in sight. And personally, I'm quite at peace with the idea that I'm aroused by a well-developed decolletage even though it isn't *actually* a shapely behind. Slightly more embarrassing is the admission that you got me to write two whole paragraphs on the subject displaying an opening image that isn't even of you!
TL;DR: Yes, YES, Desmond Morris was right, and male sexuality really is that stupid.
When it comes to male sexuality, I have my built-in limitations. I need to trust the information actual males give me. So, first of all, thank you for the input.
I think that a better argument against the extra butt theory is that naked breasts look rather little like a shapely behind. A rather small percentage of all breasts are globular in shape. A rather large percentage of all teenage girls have pendulous breasts from the beginning. I can't easily see how anyone could mistake pendulous breasts for a shapely behind.
Fine and good, yet! Bosoms do gradually become more and more bottom-like as they get larger, fuller, and more engorged with milk. At the extremes it's impossible not to notice the relationship; try searching Kristina Milan on duckduckgo (recommend safesearch on at least moderate to preserve your sanity).
Really, what makes the extra butt theory plausible is specifically the way in which it intersects with other ideas like those you've brought up here in this article - it isn't pendulous breasts that most males are after, but rather breasts that look mildly engorged.
Obviously I haven't seen enough porn. Yes, Kristina Milan's breasts actually are both natural and bottom-like, also in a totally naked state. But most women don't look like that...
I have long suspected that most males are not after pendulous breasts, and therefore I wonder very much why so many females have them from the day they develop breasts at all. It makes me speculate that round breasts in young females is a later adaptation than fat-breasts in general.
Yes... thinking about it that actually seems inevitable. I'm finding it very useful to consider the issue in a few phases, starting with our chimp-like ancestors, moving through our bipedal, erectus-ish ancestors, and then towards the modern day.
Early on, when our ancestors were barely distinguishable from chimps or bonobos, male interest in full breasts were selected for, because, such males desired their pregnant and breastfeeding mates, giving their pregnant mates some ability to secure provisioning and protection. Males without such interest sired fewer surviving offspring.
Next the ability to display large breasts during pregnancy and lactation also rose to fixation. This presumably gave rise to a visible, pendulous breast in nulliparous females. It's very hard to say when this occurred, but I'm imagining somewhere around erectus - we know that brain size was significantly increasing, and sexual dimorphism in body size was decreasing around then, and this process of pregnancy vulnerability and bonding fits with a less polygynous, more monogamous mating style.
Lastly, many females took advantage of male attraction to lactating breasts by evolving breasts of various sizes and fullnesses even outside of pregnancy; this is the point where we are now, and the trait may never go to fixation.
The more I think about it, the more I believe in your theory. At some point in pre-history, Ape started to develop into Man. Male investment in children was one important part of that process. I never really thought that a sexual fetisch could lie behind this decisive step in our history. But why not, really?
In our culture, it is customary to think of male sexuality as promiscuous and polygamous. But actually it only seems more promiscuous and polygamous than it should be according to social norms and many men's priorities: it is not completely promiscuous and polygamous. If I get you right, you propose that the typical male preference for breasts started as an anti-promiscuity adaptation. That really is an interesting thought.
That theory also makes sense seen from the female side. Catching a male is an eternal challenge for human females. If milk-breasts caught males and made them more loyal, it makes sense to develop fat-breasts and make a man invest already before pregnancy.
After much deliberation I have decided to add an opinion to this article (the total lack of comments on this blog might have influenced my decision). I guess you could call it a defense of Desmond Morris, although it is more of a variant of your own theory.
The presumption of this opinion is that the earliest hominids were "savanna chimpanzees", that is chimpanzees in a biological and social sense but who had migrated out on the savanna. The barren conditions of this new habitat should have meant that the early hominids were more sparsely populated than its forest dwelling cousins. The savanna also gave some new possibilities for long distance viewing.
In practice this could have given a situation where early hominids were as promiscuous as chimpanzees. But the scattered groups made it much more difficult to assess possible mates. A chimpanzee male who saw another chimpanzee in the distance might not be entirely sure if the other was a male (danger) or a female (mating opportunity). And if it was a female in high grass there would be no way to know if she was fertile.
That is, unless she had enlarged breasts due to breastfeeding. Even though breastfeeding chimpanzees have smaller breasts than a corresponding human female the breasts should still be an identification aid for other chimpanzees. Early hominid males could therefore have preferred to approach breastfeeding females since they were possibly fertile and at least not another male. If this gave the breastfeeding females an advantage in the mating game it would only be a matter of time before non-breastfeeding early hominids developed breasts and the chase was on.
As a bonus theory the chimpanzee on the savanna presumption could also help explain the human lack of visible estrus. The high grass and sparse population would have made it meaningless to signal estrus through the genitalia. The lower population densities might also have pushed early human males in the direction of more active fathers. If you only rarely find someone to mate with it makes sense to invest more in that particular partner and your common offspring.
Most probably there is no one single factor that explains early humans or the female breasts. But some factors are clearly more plausible than others.
Among primates in general, breastfeeding females don't want to be spotted by strange males, because those males pose a mortal danger to their children: Males who are sure they are not the father of the child has an incentive to kill it, in order to get the female into estrus sooner and father a child with her himself. This happens among chimpanzees too, although not as systematically and frequently as among gorillas.
This is the most important reason why chimpanzee females are promiscuous at all: Through mating with every available male, a female obscures paternity. Then no male can be completely sure of not being the father of the child. That is also a reason for females to mate with lurking strangers. If they lurk now, they might lurk when her child is born.
In a system with infanticide as a factor, the fundamental rule is: be as visible as possible while in estrus, and as invisible as possible while carrying an infant. Enlarged breasts just make females more visible allover.
I (and primatologists like Franz de Waal) find it likely that an important part of the investment ancestral males offered ancestral females consisted of protection. If infanticide was a problem, like in our cousins the chimpanzees, females could benefit a lot from male protection. But that was also the end of extreme female promiscuity.
The chimpanzee-human journey from promiscuity to monogamy was reasonably enough a gradual affair. Exactly where the earliest hominids, the savanna chimpanzees, were on this gradient is unknown to me. But there are still multiple points where the social circumstances would have been favorable towards females signalling their fertility on their upper chests.
For example in a social context where humanoids were slightly monogamous and lived in very scattered groups it would have been advantageous for single males to be on the lookout for "married" women who were on their own and thus candidates for seduction or rape. The slight monogamy in this scenario would consist of a male visiting regularly with gifts. Another male mating with a married female could thus hope to free ride on the support from the other male. This could also be advantageous for the female if the second male stayed around giving her support from multiple males. If enlarged breasts were the signal to attract extra males then, logically, non-breastfeeding females would start developing breasts in order to attract more gift-giving males.
Also, your reply is not really a rebuttal of my theory. The question here is not if breastfeeding females want to be seen by males but rather whether non-breastfeeding females want to be seen as breastfeeding ones. This is more about the males than the females. If early humanoid males had a preference for breastfeeding females, then early humanoid females would have been forced to simulate enlarged breasts. The interests of the actual breastfeeding females are not really important here.
The journey from promiscuity to monogamy was indeed gradual: It is not complete yet.
However, my main argument against your theory is that breasts in general don't signal fertility. They mostly signal the exact opposite to fertility: pregnancy and lactation. For that reason it is reasonable to assume that most mammal males don't feel sexually aroused by the sight of enlarged breasts. Someone breastfeeding is, mostly, someone unavailable (unless you kill her child and wait for a while).
The only way my theory can get around this problem is to assume that estrus was the baseline for sexual intercourse in ancient time. Before fat-breasts arrived, the only way males could be attracted to swollen breasts without being attracted to mainly infertile females was if they discriminated very carefully between estrus females and females out of estrus (like males of most species do). Males who are attracted to milk-filled breasts need to avoid being too attracted to females who are infertile due to pregnancy or lactation. Only an estrus marker other than big breasts can help them with that. In summary, I think your assumption that big breasts in any way could act as an estrus-marker is completely misguided.
"For that reason it is reasonable to assume that most mammal males don't feel sexually aroused by the sight of enlarged breasts. Someone breastfeeding is, mostly, someone unavailable (unless you kill her child and wait for a while)."
Mmm. You sure about that? One of the most critical problems with an arousal system is to correctly identify age, sex, and health status of a possible mating partner. An individual can usually take for granted that other creatures it's interacting with on a friendly basis are of the same species, so no trouble there, but any prospective mate must be of a reasonable age and health status; most critically, it must be of the correct sex. If you're a male chimpy-creature chilling out on the savannah, a stimulus that is breastfeeding is likely of the correct age and health status to be a possible mating partner. Without question it is of the correct sex.
To put this into perspective, we're looking into breeding cats. Friendly advice tells us that you need to remove lover boy from mommy's territory once she has his kittens. The danger isn't that he'll stupidly fail to realize that the kittens are his, and end up killing them. The danger is that lover boy will stupidly fail to realize that they're not old enough to be fertile, and end up break his baby daughters' necks trying to impregnate them. I can't say that this does actually happen, but I can definitely vouch for the idea that a male who ignores a stimulus that can't breastfeed won't have that *particular* problem.
I don't know very much about the sexuality of animals, except that of my favorite animals, the apes. From the books I have read about chimpanzees (most notably, Chimpanzee Politics and Bonobo by Franz de Waal) I know that male chimpanzees are rather good at estimating the age of a female: They discriminate against females who are too young to have given birth yet. Chimpanzee and bonobo males also only mate with females who display the genital swelling that signals estrus. Otherwise they aren't picky, but the absence of a genital swelling seems to be a complete deal breaker for them.
If big cats are so indiscriminate when it comes to mating that is interesting. I will try to find something to read about it.
Estrogen is the fertility hormone that induces breast growth.
I agree, female breasts should be viewed through evolutionary theory with hesitation. What does the research say on how the changes in diet/nutrition over the past few centuries affected the female breast size?
Well, fatter women get bigger breasts. With a few exceptions, breast size is very sensitive to weight gain and weight loss. My source for that claim is not research but just observation: Women complain that their breasts get smaller when they diet.
Here's a theory:
http://www.lloydianaspects.co.uk/evolutionaryTheories/whyWomenHaveBreasts.html#mainSection
https://www.youtube.com/watch?v=xcrxNBlqrbM
Wouldn't one reason to mate with a well-fed, breastfeeding woman be that she is likely to already have a man caring for her and her children? If you mate with her, then you can get him to invest in your child for you.
Hm. That was a difficult one. You mean, pre-human women fooled high-status males they were already provided for through looking as they were breastfeeding? And then when males found out the females were actually single they felt obliged to protect and provide for them anyway?
The important question is how male appreciation gave an advantage to women. If women evolved to have breasts, that must have been because having breasts was beneficial for women themselves.
Great point. I think the story I have in mind is that there are lots of "normal" males and a few "exceptional" males. The exceptional males are genetically desirable mates to all the females, so much so that females are willing to mate with them even if they provide little or no support. But they are only willing to mate with normal males if they also protect and provide for the children. So you could end up with an equilibrium where females enter into pair-bond relationships with normal males and have children with them. A small number of exceptional males basically sneak around surreptitiously mating with all the females as well and mixing their offspring in among the offspring of the normal males. In this way, the few exceptional males could end up being vastly overrepresented genetically in the next generation.
If these exceptional males prefer breasts, then a preference for breasts will be selected for. If females with breasts are more likely to attract exceptional males, and the children of exceptional males are more likely to survive childhood, then having breasts will be selected for. Since many of the normal males are actually children of an exceptional male father, they too are likely to prefer breasts, which just reinforces the cycle.
So why might exceptional males prefer breasts in the first place? Well, it's a sign that the female is well-fed and breastfeeding (implying she is fertile, capable of surviving childbirth, and experienced raising children). Moreover, being well-fed and breastfeeding are a good sign that she is in a pair-bond with a normal male who is protecting her and supporting her children. This makes her an ideal mate for an exceptional male because it means his offspring will be cared for by a competent mother and be well protected and provided for by her pair-bond mate.
re: . That way, having sex with a woman because early pregnancy gave her ballooning breasts seems like a very bad idea indeed.
Why should only investing in your own children be an evolutionary advantage?
Consider two groups of closely related individuals. In one group the males only invest in children who are known to be theirs. In the other group, the males invest in all of the kids in the group. If more children are successfully reared in the second group, then this is a winning strategy ... 'if we all work together we can raise more kids'.
From a woman's point of view, having every male member of the group somewhat invested in raising the children you have already made the huge investment in bringing to term is a major win.
On some level that is certainly right. In our society men invest in each other's children through paying taxes. And it has been a comparatively successful society (although it is not demographically successful right now).
Still, I don't think we will ever escape selection between individual males (and females). And in that selection those who invest in their own children have an advantage.
It's not the financial investment I am most interested in here, but the time. In Sweden, despite having plenty of divorced people and children who are growing up in two households and the like, we don't have a society of men who leave the children and child-raising to the women, while they sit around in all-male groups, drinking and smoking whatever intoxicants and stimulants are permitted by their society and perriodically killing other men and groups of other men who live in similar ways. This 'men are for drunkenness and war/defence' pattern shows up again, and again, and again when anthropologists study people, so it seems to be one that people need to take particular care to avoid in their societies.
I am reading Lars Trägårdh, “Statist Individualism: The Swedish Theory of Love and Its Lutheran Imprint,” in Between the State and the Eucharist: Free Church Theology in Conversation with William T. Kavanaugh, Joel Halldorf and Fredrik Wenell (eds.) (Eugene, OR: Wipf and Stock Publishers, 2014) right now. Facinating stuff, for me, in trying to figure out how we got the Swedish society and not something else.
However, back to the thought experiement about boobs.
Men who have _other men_ invest in their children have an advantage. Consider a society where there is perfect agreement among the females as to who is the most genetically fit male individual. In terms of genes, that one is the one that _everybody_ wants to breed with, to produce the very best outcome in the next generation, children who are 50% your genes (which you are stuck with, in your children, no matter whom you breed with) and 50% the acknowledged best male package of genes out there.
Having not invented monogamy, or anything close to it, let us say that all the women get pregnant by SuperGenePack. If SuperGenePack is the only male doing any investment in the children, then the group will raise many fewer children than groups where the men are all invested in children. Raising SuperGenePack's offspring may be a suboptimal strategy for the males who aren't SuperGenePack, but it's great for SuperGenePack. And if SuperGenePack carries a package of genes for 'my sons like big boobs' and another for 'my daughter has big boobs' these two new packages will become defining traits of subsequent generations.
In the game of numbers, 'Who gets the most grandchildren?', the stakes for women and men are not the same. Men can get a wide range of outcomes, from 'no offspring' to 'every child is my child' for the next generation. Women will get, in population terms, a very narrow range of outcomes, one that is shared with every other woman, and is based on how many pregnancies you can fit into your reproductive lifespan. No matter how much a woman might wish to have 100 children, there just isn't enough time for that. But 100 grandchildren? That could happen. One of your children needs to be the SuperGenePack of his generation.
My hypothetical situation is unlikely to be stable. There is too much incentive for the men who aren't SuperGenePack to combine forces and subdue and force fertile women to have sex with them. But a society where each woman tries to grab one male for the raising of all of her children, most of whom will be his, but who sneaks off for a little adultery with SuperGenePack may be stable. For simplicity's sake, assume that all women have the same number of children in their lifetime. Also ssume for the experiment that every woman enters into a promised monogamous relationship with one man, but sneaks off exactly once for some sex with SuperGenePack. The adultery represents her one bet on producing the next generations' SuperGenePack. The rest of the time she is just producing the usual number of children for the next generation. This is what most of the males are doing as well, they are either producing the normal number of children for the next generation or that number -1, because they are raising one of SuperGenePack's kids in addition to their own.
SuperGenePack gets the best outcome -- he gets the normal number of children for the next generation out of his official mate, plus however so many children got conceived in his very many adulteries. His genes will prosper, albeit not as rapidly as the scenario where he sired the entire next generation.
"We don't have a society of men who leave the children and child-raising to the women, they sit around in all-male groups, drinking and smoking whatever intoxicants and stimulants are permitted by their society and periodically killing other men and groups of other men who live in similar ways."
That is entirely true. But isn't that partially an effect of contraception? Women refuse to have children with men whom they believe would engage in further mating effort instead of parenting effort. The result is that we don't have many children at all. Maybe women would be willing to have many more children if more men were willing to invest.
'Mean liking boobs' cannot be an effect of contraception because human men developed the attraction long before we had any contraception, beyond lactation. 'Men are only good for violence and sex, the rest of the time the lazy bums don't do anything' is a pattern than predates contraception as well. These days women who can afford nannies and other servants to take care of their children do not typically have more children than those who have to do their own raising, so I think it will take more than 'more income' and 'more male investment' to produce larger families. (Kristina Ozturk and her husband's plan to have via surrogacy 22 children in 19 months is very much the exception.) Convincing women that the world is not overpopulated and that it is therefore not selfish to have children seems to be one of the other things that is needed.
After reading over the article again and following through the comments, I think it's worth organizing a clear response to this idea.
If I read this correctly, Tove is saying humans are unusual: adult females have breasts regardless of pregnancy status. This appears to have been a sexually selected trait. What is the explanation? Tove considers and rejects five hypotheses:
1. Extra buttocks,
2. Fat stores,
3. Handicap,
4. Age Indication, and
5. Fertility.
I don't really think these five explanations truly deserves to go to the garbage dump of ideas at https://woodfromeden.substack.com/p/the-order-of-thoughts . Some are better than others, though. #4 doesn't make sense early on, and I never considered #3 even particularly reasonable for male traits. But #1, #2, and #5 have some merit. Clearly, breasts do echo buttocks. Clearly, breasts are fat stores which may be useful. And females with breasts were at least able to become pregnant at one time. But Tove advances a different explanation:
6. MILF hypothesis. "[A]pe males have a strong preference for females who have already given birth and have the experience to raise an infant successfully....One clear marker of female self-reliance is if she is both breastfeeding and fertile."
This isn't perfect. If it were, then I think we would expect nulliparous chimpanzee females to already show breast development. Still, it does seem reasonable to think that as more maternal investment was required in childrearing, at least some males may have pursued a successful strategy of pursuing lactating females for the reasons you cite. In a similar vein, I also want to mention one other thing that I think is going on:
7. Femininity hypothesis. Signals like smaller hands and feet, high voices, and smaller stature all confuse femininity and youth. Long, lustrous hair and dark lashes do slightly better to signal femininity, but full breasts on an otherwise slender individual signal femininity very cleanly.
I don't think that #7 is actually the explanation any more than #6, though. Mammary tissue may be effective at signalling feminine sex and the ability to raise an infant successfully, in more modern humans, hip girth is a cleaner signal of both things motherhood, which doesn't also signal depressed fertility, as swollen breasts do. So what's the solution?
What I actually think is this: In the beginning, ancestral humans weren't particularly attracted to breasts and didn't form pair bonds. However, they had some mental modules related to breasts that could be co-opted to promote pair bonding.
Early hominins were likely to be slightly interested in breasts because of the ideas mentioned previously: Breasts reminded ancestral males of buttocks, they were useful fat stores, they signaled healthy femininity, and proved that a female was an experienced breeder.
As evolution progressed, gestation times lengthened from around 227 towards 280 days ( https://pubmed.ncbi.nlm.nih.gov/13646623/ ), fetuses increased in weight from 4 towards 7 pounds, and the period of infant helplessness extended towards a full year. Throughout this process mothers became extremely vulnerable for a longer and longer period. Initially this time of vulnerability may have only a been a month or two, but in the later stages of evolution it corresponded to something like the onset of the third trimester all the way to the end of the child's first year after birth. During this period, mothers and their offspring required provisioning and protection to ensure the father passed on his genes. Thus it wasn't enough for males to mate and wander away; a successful male would mate and stay. The period of greatest vulnerability would likely be exactly the time when her breasts were largest: immediately after birth.
Male hominins were already slightly interested in breasts for the reasons cited earlier. And some were likely more interested than others. As maternal vulnerability increased, those males who became excited when their partners showed signs of pregnancy would stay. Male sexual attraction to the partner would provide an incentive to provision and protect the offspring. Breasts were an excellent signal to a male that he ought to be attracted to the female who has them - particularly if she showed signs of being his particular mate (by smiling, making eye contact, and so on). When the period of vulnerability ended, the breasts went away, and he lost interest.
Probably it was only most recently, in the later stages of evolution, that females would develop and maintain breasts outside of pregnancy. With the emergence of culture, children required training and guidance, and they did better if the father never really lost interest in their mother at all. This stage never really completed in modern humans; divorce rates today peak between the 4th and 8th year. But the breasts, and human male interest in them, are still there.
Call it 8. The Paternal Provisioning Hypothesis: Mommies and babies need dad around to make them apple pie.
I think there is a reasonable explanation why nulliparous chimpanzee females don't show breast development: Because being discriminated against doesn't hurt them very much. They don't need alpha sperm for their first child anyway. Being discriminated against is much worse for human females, who can realistically hope for some male investment.
In a subgroup to the chimpanzees, the bonobos, females actually did develop a costly defense against discrimination: Since males tended to discriminate against females that did not have swollen genitalia, bonobo females evolved genital swellings that last for 3 out of 4 weeks, instead of only 1 out of 4 weeks as in the common chimpanzee.
I think your theories make a lot of sense. Especially #8: It seems to be fairly common that men find pregnancy explicitly sexually arousing. #6 more or less needs #8 to be sustainable: #6 only explains how fat breasts once might have evolved. It doesn't explain why they didn't disappear again, despite being costly. It also doesn't explain why males didn't develop counterstrategies: Being maximally attracted to females who are six weeks pregnant carries some obvious risks. #8 explains why that risk was worth taking after all.
"Male sexuality is infamous for being superficial and stupid. But is it that stupid?"
Oh my goodness yes. Haven't you noticed how Pavlovian male sexual response is? A male full of prostate fluid is really just wandering around hoping to find an appropriate place to make a deposit. Whatever signal he's primed to respond to - the scent of musk, swollen genitals, a flicking of the tail feathers, a high frequency yowl, whatever - he'll respond.
Of course the great apes are decidedly visual in orientation, not only blessed with trichromatic vision but (in the hominins, at least) a highly sensitive link from visual stimuli to erotic response. I've heard that some people are so easily excited by the sight of hairless globular fatty tissue that they respond orgasmically to mere computer images, without the need for any fertile female in sight. And personally, I'm quite at peace with the idea that I'm aroused by a well-developed decolletage even though it isn't *actually* a shapely behind. Slightly more embarrassing is the admission that you got me to write two whole paragraphs on the subject displaying an opening image that isn't even of you!
TL;DR: Yes, YES, Desmond Morris was right, and male sexuality really is that stupid.
When it comes to male sexuality, I have my built-in limitations. I need to trust the information actual males give me. So, first of all, thank you for the input.
I think that a better argument against the extra butt theory is that naked breasts look rather little like a shapely behind. A rather small percentage of all breasts are globular in shape. A rather large percentage of all teenage girls have pendulous breasts from the beginning. I can't easily see how anyone could mistake pendulous breasts for a shapely behind.
Fine and good, yet! Bosoms do gradually become more and more bottom-like as they get larger, fuller, and more engorged with milk. At the extremes it's impossible not to notice the relationship; try searching Kristina Milan on duckduckgo (recommend safesearch on at least moderate to preserve your sanity).
Really, what makes the extra butt theory plausible is specifically the way in which it intersects with other ideas like those you've brought up here in this article - it isn't pendulous breasts that most males are after, but rather breasts that look mildly engorged.
Obviously I haven't seen enough porn. Yes, Kristina Milan's breasts actually are both natural and bottom-like, also in a totally naked state. But most women don't look like that...
I have long suspected that most males are not after pendulous breasts, and therefore I wonder very much why so many females have them from the day they develop breasts at all. It makes me speculate that round breasts in young females is a later adaptation than fat-breasts in general.
Yes... thinking about it that actually seems inevitable. I'm finding it very useful to consider the issue in a few phases, starting with our chimp-like ancestors, moving through our bipedal, erectus-ish ancestors, and then towards the modern day.
Early on, when our ancestors were barely distinguishable from chimps or bonobos, male interest in full breasts were selected for, because, such males desired their pregnant and breastfeeding mates, giving their pregnant mates some ability to secure provisioning and protection. Males without such interest sired fewer surviving offspring.
Next the ability to display large breasts during pregnancy and lactation also rose to fixation. This presumably gave rise to a visible, pendulous breast in nulliparous females. It's very hard to say when this occurred, but I'm imagining somewhere around erectus - we know that brain size was significantly increasing, and sexual dimorphism in body size was decreasing around then, and this process of pregnancy vulnerability and bonding fits with a less polygynous, more monogamous mating style.
Lastly, many females took advantage of male attraction to lactating breasts by evolving breasts of various sizes and fullnesses even outside of pregnancy; this is the point where we are now, and the trait may never go to fixation.
The more I think about it, the more I believe in your theory. At some point in pre-history, Ape started to develop into Man. Male investment in children was one important part of that process. I never really thought that a sexual fetisch could lie behind this decisive step in our history. But why not, really?
In our culture, it is customary to think of male sexuality as promiscuous and polygamous. But actually it only seems more promiscuous and polygamous than it should be according to social norms and many men's priorities: it is not completely promiscuous and polygamous. If I get you right, you propose that the typical male preference for breasts started as an anti-promiscuity adaptation. That really is an interesting thought.
That theory also makes sense seen from the female side. Catching a male is an eternal challenge for human females. If milk-breasts caught males and made them more loyal, it makes sense to develop fat-breasts and make a man invest already before pregnancy.
After much deliberation I have decided to add an opinion to this article (the total lack of comments on this blog might have influenced my decision). I guess you could call it a defense of Desmond Morris, although it is more of a variant of your own theory.
The presumption of this opinion is that the earliest hominids were "savanna chimpanzees", that is chimpanzees in a biological and social sense but who had migrated out on the savanna. The barren conditions of this new habitat should have meant that the early hominids were more sparsely populated than its forest dwelling cousins. The savanna also gave some new possibilities for long distance viewing.
In practice this could have given a situation where early hominids were as promiscuous as chimpanzees. But the scattered groups made it much more difficult to assess possible mates. A chimpanzee male who saw another chimpanzee in the distance might not be entirely sure if the other was a male (danger) or a female (mating opportunity). And if it was a female in high grass there would be no way to know if she was fertile.
That is, unless she had enlarged breasts due to breastfeeding. Even though breastfeeding chimpanzees have smaller breasts than a corresponding human female the breasts should still be an identification aid for other chimpanzees. Early hominid males could therefore have preferred to approach breastfeeding females since they were possibly fertile and at least not another male. If this gave the breastfeeding females an advantage in the mating game it would only be a matter of time before non-breastfeeding early hominids developed breasts and the chase was on.
As a bonus theory the chimpanzee on the savanna presumption could also help explain the human lack of visible estrus. The high grass and sparse population would have made it meaningless to signal estrus through the genitalia. The lower population densities might also have pushed early human males in the direction of more active fathers. If you only rarely find someone to mate with it makes sense to invest more in that particular partner and your common offspring.
Most probably there is no one single factor that explains early humans or the female breasts. But some factors are clearly more plausible than others.
Among primates in general, breastfeeding females don't want to be spotted by strange males, because those males pose a mortal danger to their children: Males who are sure they are not the father of the child has an incentive to kill it, in order to get the female into estrus sooner and father a child with her himself. This happens among chimpanzees too, although not as systematically and frequently as among gorillas.
This is the most important reason why chimpanzee females are promiscuous at all: Through mating with every available male, a female obscures paternity. Then no male can be completely sure of not being the father of the child. That is also a reason for females to mate with lurking strangers. If they lurk now, they might lurk when her child is born.
In a system with infanticide as a factor, the fundamental rule is: be as visible as possible while in estrus, and as invisible as possible while carrying an infant. Enlarged breasts just make females more visible allover.
I (and primatologists like Franz de Waal) find it likely that an important part of the investment ancestral males offered ancestral females consisted of protection. If infanticide was a problem, like in our cousins the chimpanzees, females could benefit a lot from male protection. But that was also the end of extreme female promiscuity.
The chimpanzee-human journey from promiscuity to monogamy was reasonably enough a gradual affair. Exactly where the earliest hominids, the savanna chimpanzees, were on this gradient is unknown to me. But there are still multiple points where the social circumstances would have been favorable towards females signalling their fertility on their upper chests.
For example in a social context where humanoids were slightly monogamous and lived in very scattered groups it would have been advantageous for single males to be on the lookout for "married" women who were on their own and thus candidates for seduction or rape. The slight monogamy in this scenario would consist of a male visiting regularly with gifts. Another male mating with a married female could thus hope to free ride on the support from the other male. This could also be advantageous for the female if the second male stayed around giving her support from multiple males. If enlarged breasts were the signal to attract extra males then, logically, non-breastfeeding females would start developing breasts in order to attract more gift-giving males.
Also, your reply is not really a rebuttal of my theory. The question here is not if breastfeeding females want to be seen by males but rather whether non-breastfeeding females want to be seen as breastfeeding ones. This is more about the males than the females. If early humanoid males had a preference for breastfeeding females, then early humanoid females would have been forced to simulate enlarged breasts. The interests of the actual breastfeeding females are not really important here.
The journey from promiscuity to monogamy was indeed gradual: It is not complete yet.
However, my main argument against your theory is that breasts in general don't signal fertility. They mostly signal the exact opposite to fertility: pregnancy and lactation. For that reason it is reasonable to assume that most mammal males don't feel sexually aroused by the sight of enlarged breasts. Someone breastfeeding is, mostly, someone unavailable (unless you kill her child and wait for a while).
The only way my theory can get around this problem is to assume that estrus was the baseline for sexual intercourse in ancient time. Before fat-breasts arrived, the only way males could be attracted to swollen breasts without being attracted to mainly infertile females was if they discriminated very carefully between estrus females and females out of estrus (like males of most species do). Males who are attracted to milk-filled breasts need to avoid being too attracted to females who are infertile due to pregnancy or lactation. Only an estrus marker other than big breasts can help them with that. In summary, I think your assumption that big breasts in any way could act as an estrus-marker is completely misguided.
"For that reason it is reasonable to assume that most mammal males don't feel sexually aroused by the sight of enlarged breasts. Someone breastfeeding is, mostly, someone unavailable (unless you kill her child and wait for a while)."
Mmm. You sure about that? One of the most critical problems with an arousal system is to correctly identify age, sex, and health status of a possible mating partner. An individual can usually take for granted that other creatures it's interacting with on a friendly basis are of the same species, so no trouble there, but any prospective mate must be of a reasonable age and health status; most critically, it must be of the correct sex. If you're a male chimpy-creature chilling out on the savannah, a stimulus that is breastfeeding is likely of the correct age and health status to be a possible mating partner. Without question it is of the correct sex.
To put this into perspective, we're looking into breeding cats. Friendly advice tells us that you need to remove lover boy from mommy's territory once she has his kittens. The danger isn't that he'll stupidly fail to realize that the kittens are his, and end up killing them. The danger is that lover boy will stupidly fail to realize that they're not old enough to be fertile, and end up break his baby daughters' necks trying to impregnate them. I can't say that this does actually happen, but I can definitely vouch for the idea that a male who ignores a stimulus that can't breastfeed won't have that *particular* problem.
I don't know very much about the sexuality of animals, except that of my favorite animals, the apes. From the books I have read about chimpanzees (most notably, Chimpanzee Politics and Bonobo by Franz de Waal) I know that male chimpanzees are rather good at estimating the age of a female: They discriminate against females who are too young to have given birth yet. Chimpanzee and bonobo males also only mate with females who display the genital swelling that signals estrus. Otherwise they aren't picky, but the absence of a genital swelling seems to be a complete deal breaker for them.
If big cats are so indiscriminate when it comes to mating that is interesting. I will try to find something to read about it.