Thoery of Arousal
Why Women Have Breasts
Many people may suppose that the question of the title is
a stupid one, given that the answer is so obvious: women
have breasts for feeding babies. In fact, the question
is a good one, because it is a mystery why the vast majority
of women has breasts. Most women are, at this moment, not
lactating, and yet they have breasts. If breasts were merely
for feeding babies, then most women would not have them.
They would develop them only during pregnancy, and would
lose them again when they stopped breast-feeding. Humans
are unique in the animal world, in that they develop breasts
at puberty and retain them into old age, whether or not they
ever get pregnant. This requires an explanation.
A heifer develops an udder when it is time to produce milk
for feeding her calf. Once the calf has stopped feeding,
the heifer (now a "cow") dries up and the udder
disappears. Growing an udder, like any body tissue, is
a cost. It takes nutrients to grow and maintain the udder,
and the udder itself is a hindrance to quick movement. Indeed,
prominent udders are not necessarily needed at all. Seals
manage to feed milk to their young without any such protuberances
which would spoil their hydrodynamic form. A woman pays
a cost in nutrition and agility by growing breasts when
she doesnt need them. If there is a cost, then there
must be a benefit to explain why this human trait has evolved.
Given that the trait is unique to humans, it is very likely
indeed that the explanation will be found in some other
characteristic that is unique to humans.
There is surprisingly little literature on this topic.
There are a few short papers, many written long ago, and
most of which have been soundly criticised by more recent
writers. There is little point in repeating the demolition
of several early theories here. See the bibliography for
further reading (Cant 1981 especially).
Herbivorous women, carnivorous men
Our ancestors were hunters, who survived principally
from eating other animals. With other hunter species,
like dogs, cats, and stoats, the adult females hunt, unless
perhaps they are heavily pregnant or tending young offspring.
Hunting is difficult enough without udders, and so the
hampering effect of udders is minimised - they only grow
them when lactating. Herbivorous herd beasts like cows,
sheep, and deer must be able to escape predators by running
faster than their neighbours in the herd, and so one with
useless udders is just asking to be eaten. Most mammals
rely on speed to escape being eaten, so even solitary herbivores
would be badly advised to grow udders until the proper time.
Humans, however, are importantly different, in that they
do not rely mainly on speed to escape predation. Few animals
will attack a group of humans, and humans will use group
tactics, fire, weapons, missiles, and the like to defend
themselves. Any animal powerful enough to bring down an
animal as big as a grown woman, can out-run her so easily
that speed of foot is not the issue. Human females gather
food in groups, and in parts of the world where this is dangerous,
tribes post armed teenage boys, and the occasional older
man, to guard them. Much of their time they spend in camps,
in the presence of fire, and very few animals will venture
there. Human females, therefore, paid a much smaller price
for developing udders than other animals, during their
evolution. Very few women in the Pleistocene of child-bearing
age would have been lost to predators. They were free to
be hampered by non-lactating breasts.
In other words, division of labour made nulliparous breasts
possible. Our ancestral fathers behaved like carnivores,
and needed to be able to run and jump freely to hunt, and our
ancestral mothers behaved more like herbivores, harvesting
in groups. A nullipara is a female who has not yet borne children.
It is an interesting quirk of our culture that we all know
the word virgin, but few know nullipara.
The above explains how it could have been possible for non-lactating
breasts to evolve, but it still falls a long way short of
saying why they actually did evolve.
Beautiful plumage, beautiful breasts?
Once it has been established that it is possible for breasts
to evolve, then an evolutionary scientist can argue that
breasts can evolve as sexual characteristics. They could
be like peacocks tails arbitrary signals
to the opposite sex. Peacock tails are big, fan-shaped
and green, with lots of eye-spots. Other
birds have long tapering tails or bright red plumage. It
seems that it doesnt really matter what sort of
plumage evolves, as long as it belongs recognisably to
a certain species, and as long as the opposite sex develops
a preference for it. Once peahens start finding fan-shaped
green tails with spots sexy, then it is in their interests
to mate with the male with the best tail of that description.
Human breasts could have evolved in the same arbitrary
way. This can lead to Fisherian run-away selection
which very rapidly causes a species to evolve such things
as bright plumage, wattles and combs, and, perhaps, breasts.
Fishers logic would say that once men start to find
breasts attractive, women have selective pressure on
them to grow them, and thus do such women become sexier,
and thus is there a greater pressure on men to find them sexy.
The classic Fisherian example is the peacock's tail,
and I apologise to evolutionists who have read about this
too many times already. In peacocks, however, the males
are the pretty ones. In humans, somehow this is reversed:
women are the pretty ones, and men are all astonishingly
ugly. In most species, the females are the replicators,
and must be sensible about camouflage and the like, and
so can't afford to be showy, but even if most of the males
die because of their hampering plumage, this doesn't
matter, since those left can fertilise all the females,
and will probably have the best genes anyway, since they
managed to survive. This occurs in its most extreme form
in species where the males play little or no part in the rearing
of offspring. Humans have fairly high male parental investment,
however, and so the males are more valuable, and as said
before, mortality due to predation in adult females, even
those hampered by udders, would be so low, that this rule
could in humans be sex-reversed.
That breasts were selected for by sexual selection is convincingly
argued by Geoffrey Miller in his book The Mating Mind (2000).
Like other such traits, they exaggerate the different
between the sexes; they are invisible on the skeleton;
they vary greatly between individuals; they enlarge after
puberty; they engorge with blood during sexual arousal;
all cultures value them as sexual symbols and many mutilate
them for sexual offences; all around the world they are
emphasised to look sexy or played down to avoid sexual attention.
That breasts vary so much in size is a good clue to their not
being utilitarian like hands or eyes. Pre-lactating breasts
consist mainly of fat. Lactating breasts produce the most
milk about eight months after the start of lactation. During
the first eight months of lactation, however, the breasts
are at their largest. It seems that the fat is actually hampering
to milk production, and that it takes eight months to change
the design of the breast to maximise efficiency, and get
rid of the decorative fat.
A peacocks tail seems to have some innate qualities
of beauty, in that humans find them beautiful, and they
were not designed for us to gaze upon. A human breast involves
a circle within a circle within a circle, all presented
to the viewer. It is easy to imagine that there might be some
innate beauty in this design. The nipple is not placed for
efficient feeding. When tapping a barrel, one does not
put the tap half way up the barrel. A much more efficient
nipple would be on the bottom of the breast. This would be
better for getting milk to (gravity feed) and easier for
the infant to suckle from. One possible explanation for
the location of the nipple is that it accentuates pertness
when it points upward, and hides sagginess, in that it almost
never points directly downward (see below for why this
might be important). Another is that the geometric perfection
of the design allows the viewer to see the tiniest of imperfections.
The eye can detect very easily whether a circle is properly
circular or not, and whether a circle within it is exactly
at the centre. If a breast's form is for display, then
its design might be expected to be something which is particularly
difficult to get just right.
Breasts, when not lactating, have an important decorative
function.
So, the bigger the better, right?
If Fisherian run-away selection got a hold on the evolution
of the human breast, then one might expect breasts to get
ever bigger and bigger. The process has a number of limiting
factors, however. For a start, breasts still do have another
important function: they will be needed one day for feeding
babies. Women with very large breasts report that they
find it very difficult to breast-feed their babies. The
infant finds it difficult to latch on to the nipple, and
the baby can be smothered. Often, the heavily-encumbered
mother will need both hands to feed the baby. In the environment
in which our ancestors evolved (the EEA
Environment of Evolutionary Adaption), breast-feeding
would have been vital. Without mothers milk, the
baby would die (1). Breast-feeding can take a lot of time,
and Pleistocene babies may have been breast fed for longer
than modern babies. It is unwise to underestimate the cost
of the loss of time which needing both hands to breast-feed
would incur. Frequent small feeds are far more efficient
and comfortable for the mother than infrequent larger
feeds. Storage of milk in the breast for more than a few hours
leads to a prompt reduction in milk production, and breasts
can become uncomfortably engorged. Our female ancestors
would have wanted to get on with tasks such as food gathering,
suckling their infants as they went, and they might do this
for two years per child.
Another false bigger is better argument
is that which says that a man will find big breasts sexy because
he knows that any children he fathers by the breasts
owner will not go hungry. In fact, the breasts on a nullipara
contain mainly fat, not milk-producing tissue. They are
almost no indication at all of the amount of milk a woman
might produce in the future. Breasts typically increase
in size for the first eight months of lactation. Besides,
an ability to produce more milk than is needed is no advantage.
Once a woman has produced enough to feed her baby well, any
excess production is expensive waste. Almost all women
can produce enough to feed a child. Milk production increases
to meet demand, so a woman bearing twins will produce more
(2).
Another limitation on the size of breasts would be that
the larger they get, the sooner that gravity will take its
toll over time. Low-drooping breasts are a sign of age,
and in all cultures youth is sexy in women. A young bride
will probably bear a man more children than an old one, so
it is unwise to grow breasts which make you age more quickly.
Another limitation is that the larger a pair of something
gets, the harder it becomes to keep the pair symmetrical.
The symmetry of a body is a good clue to health and fitness,
and seems to be considered important in judging mates in
most species, including humans. Only very healthy women
would have been able to grow a large and symmetrical pair
of breasts.
It is possible, therefore, that Fisherian run-away selection
took place in the evolution of the human breast as a sexual
ornament, but that a few factors then later put a limit on
the degree of change in the human form.
Theyre sexy, you fool!
The next obvious answer to the mystery is that men find breasts
sexy, and that is why women have evolved them. Again, however,
this does not suffice. Yes, men do find breasts sexually
attractive, but the question is why do they find them sexy?
One could say that we get food because we like eating. This
is not an answer to Why do we get food? We
get food because if we dont eat we die. We like eating
because people in the past who enjoyed eating worked harder
to get food, and passed on more genes as a result. Pleasure
has a purpose other than itself. Men must find breasts sexy
because they signal something worth knowing. That they
find breasts especially sexy suggests that breasts are
a very reliable indicator of some good trait in women
that they are honest indicators.
One objection to all this is the claim that men from cultures
in which the women habitually go about topless, do not find
breasts sexy. I refute this: we do not say that womens
faces are sexy, largely because we see them all the time,
but were I to show a photograph of Celia Johnson's head
to any red-blooded Englishman, then he would surely say
that the image he sees is one of an attractive woman. Any
body part of a woman that conveys information of her good
qualities to a man is sexy.
Rival theories
Dr. Boguslaw Pawlowski of Wroclaw suggested a theory to
explain permanent breasts in 1999. He writes that humans
evolved a layer of subcutaneous fat for insulation against
the cold of a new environment, after our species stopped
living in trees in forests, and moved out onto the plains.
The same hormone, oestrogen, is responsible for the growth
of this fat in girls, and the development of breasts. Having
breasts would be a sign of having a fair amount of fat, and
men would find this sexy, because fatter women would give
rise to fatter children, who would survive better. A snag
with this is that men too would surely have benefited from
this subcutaneous fat, and men have far less of this than
women. He explains this away by writing that the oestrogen
that created the fat would have disturbed the masculinization
process in males, and that males had to be nimbler,
for hunting and fighting. I'd have thought that even
a nimble active man might freeze in the night if a layer of
fat could make the difference. Even men have to sleep sometimes.
That fat is important to women is pretty certain. To become
fertile, a woman has to have a certain amount of fat on her
body (3). In the past, it would have been a lot more difficult
to become fat. Modern diets make this easy. Today, most
successful professional female athletes in track and
field events are so lean, that they are not fertile. They
do not ovulate. Men have evolved to find fertile women sexy,
and infertile women unsexy. Naturally enough, most men
prefer the curvaceous look of glamour models to the lean
look of infertile athletes (Polivy 1986). This is reason
enough for women to put on a bit of fat. That women did not
have to hunt in the ancestral past also means that they were
free to put on fat, and the benefits of food storage and insulation
were probably useful too, and worth having since the costs
of being a little plump were low.
Breasts could be a signal to a man that a woman has put on enough
fat to be fertile. I do not find this explanation good either.
Humans are very good indeed at gathering information from
a glance at another person. Women could signal to men that
they have enough fat to be fertile, simply by having enough
fat to be fertile. It would show (4). Also, if men saw breasts
as a cue to adequate fat for fertility, then women might
evolve to grow breasts or not to grow breasts, as a dishonest
signal. They might hide their fat by growing no breasts,
or might suggest that they were fat and fertile by putting
what meagre fat resources they had into deceitful breasts.
This does not accord with observation. If breasts were
simply a cue to a fat reserve, then why can men find the combination
of large breasts and slender body attractive? Why would
a woman who is very fat still have to grow breasts? Singh
(1995) found that men preferred large breasts and symmetrical
breasts, regardless of what the rest of the woman looked
like, for both long and short-term relationships.
Pawlowskis theory in my view suffers from the weakness
that it relies to a great extent on the effects of hormones.
It is a common error to believe that hormones have some innate
effect. Imagine that a man is a forward observer for the
artillery in a war. He is told to fire up a green flare if he
sees the enemy approaching in the west valley, and a white
flare if he sees the enemy in the north valley. He sees the
enemy in the north and fires a white flare. A few minutes
later, he spots a mass of explosions amongst the enemy troops.
My goodness! he thinks to himself, This
flare gun is powerful! In fact, the flare gun had
no effect whatsoever on the enemy. It was an arbitrary signal
to the hundreds of artillery crews behind him. The crewmen
responded to the signal by following a pre-arranged plan,
and firing at a map grid reference. If the artillery crews
had not been there, or had not been told what a white flare
meant, the flare would have had no effect. Another week,
different codes might be arranged, and a white flare could
mean something else entirely.
In animals, hormones are like those signal flares. They
have no innate effect, and the response is variable. The
same hormone can have one effect in one species and another
in a different species. It can have a different effect on
a given animal at different stages in the life of that creature.
The same hormone in different individuals of the same species
can lead to different responses. Creatures evolve different
reactions to the presence of hormones. Human females evolved
the response of growing breasts and subcutaneous fat in
response to oestrogen. They also evolved many other responses
to the same chemical. Testosterone would be a remarkable
chemical indeed if it could cause both a deep voice and a
beard. The truth is that it is a signal, and men have evolved
to respond to that signal by growing beards and growling.
They might have evolved to develop patches of green skin
on their ears in response to testosterone, but they havent.
That the same hormone causes women to grow breasts and to
grow subcutaneous fat does not explain the fact that women
grow breasts. Women with Cushing's Syndrome become
very fat due to a hormonal problem, but they do not grow large
breasts. Here, cortisol, not oestrogen, is the hormone
at work (5). The womans body reacts to the signal
by growing fat on the body, but not by growing huge breasts.
If the fat were for insulation, then putting fat into breasts
would be inefficient. It seems that the body can develop
mechanisms to grow insulating fat without growing breasts,
and if it can, then it would. There must be another reason
for permanent breasts.
The big snag
I feel that where most other theories fall down is that they
dont start far enough back in time. There is every
reason to suppose that there was a time when our ancestral
mothers did not have breasts when they were not lactating.
We share common ancestry with chimpanzees, and these do
not have permanent breasts. At some point in the past, proto-humans
only grew breasts when they needed to lactate. If permanent
breasts evolved as a sexual ornament, then we must first
think what the lusts of men at that time might have been.
If breasts only developed when milk was needed, then when
a man saw a woman with breasts, he knew that she was either
about to give birth, giving birth, or breast-feeding a
young child. A pregnant woman cannot be made pregnant with
a new child. A woman giving birth is busy. A woman breast-feeding
a child is very difficult to get pregnant. Breast-feeding
is an effective contraceptive. Today it is possible for
a woman on a modern high-fat diet to get pregnant while breast-feeding,
but in the Pleistocene it would have been an unusually well-fed
woman who managed this feat. Breast-feeding spaces out
births in hunter-gatherer populations. Therefore, a
pair of breasts was, to an observing ancestral man, a lot
like a flashing neon sign saying, Im infertile.
Dont bother trying to copulate with me, youd
be wasting your sperm would be to a modern man.
In short, breasts were once a turn-off, not a turn-on. It
is thought that women in the Pleistocene may have spent
about half of their fertile years lactating, far more than
is typical today. The presence or absence of breasts was
therefore a very important signal to the men of the time.
Men will evolve the lustful instincts appropriate to the
women of their time. Therefore the evolution of permanent
breasts has a huge hurdle to clear. The first women with
nulliparous breasts would have had a terrible handicap
when it came to attracting good mates. A mans instinct
would warn him not to mate with such a woman, because she
would seem pregnant already, so her first child would not
be his, and she would not be able to produce a child of his
for a long time. He would be mistaken, but if he acted on this
belief, then the woman would be less likely to mate.
Once this hurdle is cleared, then breasts are free to evolve
either as Fisherian arbitrary traits, or as advertisements
of good genes of various sorts. Until it is cleared, all
the other explanations are useless.
Women are special
Women are humans, despite what many male observers may
tell you, and humans are different from the rest of beasts
in many ways. Just as I used the uniqueness of humans to explain
why breasts were free from the costs of encumbrance to evolve,
so too will I use the specialness of humanity to explain
how the first women with permanent breasts managed to overcome
their problem.
If the first women with permanent breasts were good examples
of womanhood, then surely it is not incredible that they
managed to persuade some men to mate with them. Women have
sexual desires too (I have this on excellent authority),
and so they would have a motive to achieve this feat, especially
after being on the shelf for some while.
Women are secretive
Another odd thing about humans is that their females ovulate
on the sly. The current accepted theory for this is that
women ovulate in secret to keep men guessing. If a man knows
that a woman is not fertile, then he is unlikely to make the
effort to please her children, please her, provide meat
for her, and such like, and he is motivated to seek more fertile
mates elsewhere. Male chimpanzees are not very interested
in females unless they have big pink rumps which signal
that they are fertile. A man kept in the dark has to play the
game of developing a long-term bond with a woman, and will
mate with her many times before getting her pregnant. Women
at their fertile peak are more likely, recent research
indicates, to have affairs with sexy men. All this is to
the advantage of women, and the disadvantage of men. If
women evolved this secrecy for their own benefit, then
the fact that they still only grew breasts when they were
pregnant would threaten to ruin the whole effect. Breasts
meant lactation, and lactation meant children and temporary
infertility. This is information men can use to their advantage.
I suggest that one reason that permanent breasts evolved
is to maintain the full advantages of secret ovulation.
My thinking is that secret ovulation and permanent breasts
evolved at about the same time.
How they did it
Those cunning first women with permanent breasts were
able to get access to the best sperm in their districts.
They were able to do this thanks to several advantages,
including any or all of the following:
Women can talk, and can lie more efficiently than other
animals. With these powers, they could get access to the
men of their dreams, and to their sperm, despite the drawback
of having breasts. Humans are social animals that live
a long time. A man could have developed a fondness for a woman
he knows because of her charming personality, her wit,
and her kindness. When presented with an opportunity to
mate with such a familiar woman, a scenario he has perhaps
imagined a hundred times, he may well be persuaded to copulate
with her, even if he is a bit put off by those wobbly things
on her chest. He can always close his eyes to them.
The mates of these first women with permanent breasts would
probably not have been very vigilant in guarding sexual
access to their women, because the women were apparently
not very fertile. When a woman produced a child, thus proving
herself to be fertile, her mate would only become wary of
rivals for her affections when her breasts disappeared.
Until, then, hed think wrongly that he could relax.
Men would not have written-off women with breasts as forever
infertile. Eventually, they would feel, a woman with breasts
would flatten out and become fertile again. Accordingly,
men would often bother to develop relations with the nice
women in their area, even during periods when these women
were infertile. An established relationship, even a non-sexual
one, is an advantage to a woman wanting an affair with a man.
This is another human thing. Though male chimps can afford
to ignore non-fertile females, men would be more foolish
to do so.
The contemporaries of these women would probably have
had different instincts from women today. With obvious
menstruation, a creature does not evolve to be lusty when
infertile. Women would have evolved to be fairly lustful
only when in a fertile part of their cycle. Even today, this
is when they are at their most lusty. A man seeing a woman
with breasts would naturally feel that she would not try
to cuckold him, because she would not be lusty. Thus could
the first women with hidden menstruation and permanent
breasts find it easier to sleep around, thanks to the lower
vigilance not only of their male mates, but of their female
rivals, whose mates were going through a relatively sex-free
period.
Possibly, men of the time had instincts, which may now be
lost, that encouraged them to provide food for women with
breasts. Women with breasts would be breast-feeding,
and so in need of a bit of extra food. A man seeing his mate
with breasts would continue to provide for her, to go out
hunting for her, leaving her to get sperm from elsewhere,
and he might well continue to provide for her as she brought
up the resultant bastard child.
The children produced by this cuckoldry, were probably
above-averagely good, because the women would have used
their powers to get the best sperm, and the fact that they
succeeded shows that they were probably fairly high-quality
women to start with. Thus did the genes of these women have
a good chance to replicate.
That these first women with permanent breasts would have
been found less sexy because of their breasts is near certain.
It is equally certain, however, that they did overcome
this disadvantage. That women today have breasts is proof.
If no man ever wanted to mate with a women with breasts, the
only women today with them would be lactating.
The evolutionary pressure on men to get rid of an out-dated
instinct, that of finding breasts repulsive, would have
been very great indeed.
Big bang day
Suddenly, the world for men had changed. Whereas once the
instinct to find breasts on women a turn-off was a good thing,
in a short while this instinct had become a disadvantage.
If one man in the tribe of permanent-breasted women were
to be the only one who was not turned off completely by breasts,
then he would father the whole of the next generation, and
male instincts would change very rapidly indeed. Im
not suggesting that anything so extreme or literally sudden
occurred, but my feeling is that the change of male instinct
would have been very quick by the general standards of evolution.
Instincts are coded for by genes. Genes are made up of DNA
strands which use a sort of language, Gattaca. In English
words, a mans instinct may have been quite simple,
and something like the following:
Look at women, and see if they have a pair of round
wobbly things on their chests. If they have such a thing,
feel sexually repulsed. Increase this feeling as they
are bigger, rounder, wobblier.
One might argue that a man with such an instinct would do
well, in the light of the changes in the bodies of women,
to delete this programming entirely. However, a much smaller
mutation could alter the programming to:
Look at women, and see if they have a pair of round
wobbly things on their chests. If they have such a thing,
feel sexually stimulated. Increase this feeling as they
are bigger, rounder, wobblier.
Only one word of the English has been altered. The instinct
is pretty much the same, in that it identifies the breast,
and engages an emotion based on some assessment of that
identified thing, and an emotion to do with sexual feeling.
My guess is that it was much easier to flip the instincts
of men from one extreme to the other, than from one extreme
to neutrality. Also, if evolution really was moving very
quickly, then there may have been a sort of race on to develop
a more appropriate instinct for men to have. The simplest
solution may have won the race because it was the quickest
to implement, not because it was the best solution. In a
world where most men found breasts a turn-off, and in which
many women had permanent breasts, a man who found breasts
positively stimulating might well pass on more genes than
men with more moderate opinions of breasts. Mens
lust for breasts could be one of the scars of evolution
a thing which is not optimally efficient, but the result
of the particular path which brought us to the present.
Women would have evolved permanent breasts before men
evolved to find them sexy. The two changes would have overlapped
in time, but the start of the process must have been the breasts,
not the lust. If the breasts came first, then an aversion
to them would be disastrous for a man. Putting it at its most
unrealistically extreme, in a world where all women have
breasts, a man averse to them would probably not breed at
all. In the rush to avoid this disaster, Nature might over-shoot
a bit, and give men an instinct of attraction to breasts
which is disproportionate to the true value of them. Men
might find breasts so very sexy because they used to find
them such a definite turn-off. The aversion was probably
pretty strong, as strong as a young man's aversion
today to mating with a very old woman. There really is no
point in mating with someone who is infertile, so instincts
will go a long way to avoid this.
One reason I have for suspecting that this is true, is the
observation that men find almost all breasts sexy. By and
large, people make qualitative judgements regarding
the attractiveness of those around them. That a woman has
skin does not make her sexy. All women have skin. Smooth,
healthy, blemish-free, youthfully-taut skin is attractive,
while rough, blotchy, sagging skin is positively repulsive.
A man is attracted by the quality of the womans skin,
not its mere presence. While it is true that men do make some
qualitative assessments of breasts, it seems that almost
all young women have breasts which enhance rather than
detract from their sexiness. A reversal of the instinct
to find all breasts a turn off would explain this.
Another reason to believe this is that if mens instincts
of lust matched the fertility of women perfectly, then
men would find large breasts the least attractive, because
a womans breasts are at their largest when she is
breast-feeding a young baby, and at this point in time she
is infertile. Men would find breasts sexier as they got
smaller, because as a woman continues to breast feed, her
breasts get smaller, and she becomes steadily more and
more fertile, as the contraceptive effects of breast feeding
fade away. This is clearly not what we find in the real world.
Yet another reason to believe that mens instincts
on breasts flipped from aversion to attraction, is that
men find super-normal breasts attractive. Today it is
possible for plastic surgeons to create breasts that were
impossibly large in the Pleistocene. There are women who
make a significant amount of money by having their breasts
enlarged to farcical hugeness, and then working as strippers
and photographic models. It seems that the instinct that
programmes a mans lust is quite simple on this matter.
This reminds me of an experiment I saw demonstrated once
in which the young chicks of a species of gull were presented
with a variety of things, and it was recorded how often they
pecked at them. The adults of this species had a reddish
patch on the underside of their beaks. When the chicks pecked
at the patch, the adult regurgitated food for the chicks.
The chicks pecked hardly at all at the beak of a real live
adult, which had had its patch painted out. The chicks pecked
most of all at a ping-pong ball which had been painted with
glossy scarlet nail polish. It seems that the chicks paid
no heed to the fact that a living, moving, familiar, gull-shaped
object was next to them, nor to their memories of what had
fed them in the past, nor to the smell of a parent just back
from hunting in the sea. Instead, their instinct was just
feel the urge to peck at round red things, the rounder
and redder the better. My feeling is that men have
a similar instinct when it comes to breasts. True, men prefer
real breasts to fake ones, but that they are fascinated
by huge breasts is undeniable.
The last hurdle
If the first women to have permanent breasts were poor specimens
of womanhood, then the men who chose them for mates might
have few descendants today. Only if these first women,
with their prototype encumbrances, were at least adequate
examples of baby-producing machines, would evolution
have favoured men who found such upholstery appealing.
I have to be able to show that these first women with ever-present
breasts, bizarre mutants though they were, were up to the
job of becoming our ancestors.
If you followed my argument in the last section, then you
may agree with me that this last hurdle is circumnavigated
by this theory. Yes, a lust that attracts men to something
other than the most fertile and high-quality women is going
to be out-competed by a more optimal lust. But a lust which
attracts men to women who are probably no better nor any
worse than other women, and which allows those men to cuckold
their rivals, will do very well indeed. I have no reason
to suppose that the first women who kept their breasts after
their first pregnancy were in any other way different from
their rivals. If they had given birth once and lived, then
they were at least adequate, and these women would get the
best sperm, and so the resultant children would be at least
as good as the mothers.
Evolution is a process with a strong random element. It
could be that the first women with permanent breasts just
happened to have been good examples of womanhood, even
if they could never run using both arms.
The nulliparas join in
The lusts of men at some point in the past altered to find
breasts attractive. Once men had developed this lust,
then it would become to the advantage of nulliparas to resemble
their more mature rivals. I suspect that women evolved
breasts which didnt disappear after breast feeding,
and that this led to the evolution of mens lust for
breasts, and that following this, nulliparous breasts
evolved in response to the new lust.
If men find breasts sexy, then a young woman will do better
with them than without. This way, she is likely to win a better
mate, and start breeding when younger and so produce and
raise more children. The breasts she has have no lactation
function whatsoever. They are totally useless except
for making her sexier in the eyes of men. In the past, young
women with no breasts were no less sexy for lack of them,
but once some women had permanent breasts, then all women
had to be burdened by them.
The situation today
Today men do find breasts attractive, and breasts are permanent
features on women. Once human evolution first reached
this point, then breasts and the lust for them could start
to evolve as Fisherian traits, influenced by sexual selection.
One characteristic of a sexually selected trait is that
it varies a lot. There is great variation in human breast
size. It seems likely that breasts are now sexually selected
traits.
The peacock's tail works largely because it is an honest
signal of good genes. If it were a signal, of any kind, of
bad genes, then it would not have evolved. To survive and
grow a magnificent tail, a peacock must be fit, strong,
free from parasites, and well-fed. So when the peahens
choose the peacock, they are picking a good one if he has
a huge shimmering tail. If peahens preferred peacocks
with drab, asymmetrical, damaged tails, then they would
probably be picking badly-fed peacocks, who had had several
close escapes, and who might be parasite-ridden, and thus
they would not be combining their genes with the best available.
If the human breast is like a peacocks tail, then
one would expect men to find some breasts more attractive
than others, and that these would be the ones most difficult
to grow.
J.T. Manning et al. (1997) note that high oestrogen levels
in women are associated with a less good immune system.
This suggests that only very healthy women can afford high
oestrogen levels. Large breasts could therefore act as
a peacocks tail, by advertising a handicap. Just
as a peacock can survive and thrive despite its tail, so
a woman could survive despite a suppressed immune system.
One reason that a woman with large breasts might be sexy
is that she might be advertising the fact that she is easy
to impregnate. This might be because large breasts signal
a good supply of oestrogen, and one effect of oestrogen
is to make more permeable the zona pellucida, the membrane
of the egg. It also affects the pH of the endocervical mucus.
Sperm therefore would have an easier time fertilising
the egg of a woman with large breasts. Note that this reasoning
does not explain why women might grow breasts in the first
place, but it might explain why men find large breasts sexier
than small ones. These last two paragraphs both use the
effects of hormones as part of the argument, and so are weakened
by what I said above about hormones. However, now I am writing
about the variation in modern breasts, not about why breasts
evolved in the first place, and in this context the strength
of such arguments is much greater.
I wrote earlier that the fact that large breasts sag more
quickly is a limitation on the size of breasts. One might
also argue that large and pert breasts are therefore proof
of youth. It might be in the interests of a woman with a short-term
mating strategy to benefit from this proof, even though
she will pay the cost later. I consider this to be a very minor
factor, if any, in the evolution of breasts, not least because
if it were a major factor, then I would expect women to evolve
the refinement of breasts which were large when young,
and then decreased in size later, so as to minimise the drawbacks
of sagging. Also, there are many other reliable cues to
youth, such as young-looking skin. It is relevant to note
that the careers of women pornographic models seem to be
extended by many years, if they have large breast implants.
One might argue that these large artificial pert breasts
succeed in making the women appear younger. However it
could be that the lust inspired by their large breasts merely
compensates for the fact that men can see that these women
are no longer young. I was considering illustrating this
point with a photograph, but have decided against it.
Symmetry is a good guide to health. Many studies have strongly
suggested that humans and other creatures judge a symmetrical
body to be a good body. Certain parts of a person are particularly
tricky to grow symmetrically. The face is one such part,
and people judge beauty largely by the face. Small breasts
are easy to grow symmetrically, but as breasts become larger,
it becomes more and more difficult to grow them symmetrically,
and any asymmetry shows more definitely. To grow large
and asymmetrical breasts would be to advertise deformity,
and be bad for the reproductive potential of the woman.
Manning and others (1996 revised 1997) have pointed out
that women with large breasts have surprisingly symmetrical
breasts, much more than would be typical of body parts in
general. This suggests that only women capable of growing
symmetrical large breasts, grow large breasts, which
fits the idea that they are an advertisement of health.
That breast symmetry matters might be reflected in the
fact that Manning (1997) found that married women have
more symmetrical and slightly smaller breasts than unmarried
women. Again, this argument only explains the sexiness
of large breasts, not the existence of breasts in the first
place.
Miller (2000) points out that a single impressive sexual
ornament can suffice. A peacock must be healthy if it has
grown a fabulous tail. It does not have to grow two such tails
to prove itself. One tail is an honest signal, and an honest
signal is proof. Miller contends that the human brain,
with its capacity for humour, music, oration and the like,
is a sexual ornament. This would mean that a woman who is
very intelligent would already have proven to the world
with her wit that she has good genes and is healthy. She would
not need large breasts to get her man. A woman of lower intelligence
would need to do something to convince a man that she was
worth wooing. If she had not the wit to make a man stay with
her for many years, copulating with her often, and helping
raise her children, she could compensate by at least advertising
that she was easy to impregnate. Men would find such women
especially attractive, since they may appear to offer
a man the jackpot: a child without the responsibility of
parenting a child.
That women do vary their behaviour according to their own
brand of attractiveness is supported by a number of observations.
For instance, women who have sexier bodies, rather than
pretty faces, are more likely to indulge in casual sex,
and lose their virginity three years younger. They also
put more emphasis on the physical attractiveness of their
partners, and in other ways tended to be more masculine
(Mikach and Bailey, 1999). This is possible partly because
a woman can be exposed in the womb and during life to testosterone.
Some women have high levels of both sex hormones, and testosterone
makes people lustful. Women with large breasts achieve
menarche (periods) earlier, and get married less often
(Manning, J.T. et al., 1997). This suggests that the instincts
of women are fine-tuned to their best reproductive interests,
and that breasts are sexy. A woman who is likely to succeed
in the long term, due to beauty and brains, may grow smaller
breasts and wait longer before losing her virginity. Another
option for a woman is to become as sexy as possible as quickly
as possible, and start breeding as young as possible. This
doesnt mean that they are not fussy about the men
they mate with, but it does mean that they would put less
weight on how long those men stayed with them. They could
get the best sperm by being sexy, rather than being intelligent,
but they can only get the best sperm this way when they are
young, so they go for it. There is supposedly
a link between high levels of sex hormones, both oestrogen
and testosterone, and lower intelligence, which fits
this pattern. This would also fit the frequently noted
phenomenon of women thinking little of the intelligence
of busty young sexy rivals of easy virtue.
Another benefit of having breasts is that they increase
the size of the chest, and so decrease the relative size
of the waist. To an observer, a womans waist looks
thinner if she has breasts. A man will find a fertile-looking
woman sexy, and a pregnant woman is not fertile, so a womans
looking as though she has no bulge at the waist will make
her sexier (see my theory on fat thighs).
So, now that women are obliged to carry breasts around with
them all the time, it seems that many of them have taken the
trouble of growing good ones.
Men, meanwhile, are stuck with a sub-optimal instinct.
Their desires are fired by a pair of useless bags of fat.
Men cannot afford to lose this instinct, however. Non-lactating
breasts are like nuclear missiles we only need
them or want them because other people have them.
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