The Human Animal (1994–…): Season 1, Episode 4 - The Biology of Love - full transcript

For millions of years our ape ancestors lived in the trees.

But then they came down to the ground, and in an evolutionary leap

that was to advance them over all other species,

stood up on their hind legs.

It was a critical stage on the way to becoming modern man.

But there was an unavoidable consequence to our becoming upright.

Suddenly the sexual organs were now frontally exposed

in the male

and the female. This was to have a profound effect on our

sexuality then and now. Today, all our lives are affected by

that one simple anatomical fact.



OpenSubtitles recommends using Nord VPN
from 3.49 USD/month ----> osdb.link/vpn

I'm a biologist, and this is a program about human courtship.

But if you think I'm going to be concentrating on

human sexual behaviour, you'll be wrong.
With the human animal, love

is much more important than sex.

But what is love anyway?
Is it purely a human emotion?

In the animal kingdom,
as you move from group to group

you find huge variations in the way
sexual behaviour is organized.

Some animals have gaudy sexual signals.

Some do not. Some mate for life.

Most do not. In some species the
males mate with as many

females as they can cover. In other species

it's the females that control the time and place of mating.

Some animals indulge in
elaborate courtship displays.



Our nearest relatives

however have little or no courtship.
Some fathers play a

role in bringing up their young.

But most offspring are brought up with no paternal help.

Since the 1950s when I first began

my studies of chimpanzees at London Zoo,

I've been fascinated by this species,

our closest relative. Chimps are in fact, so close that

we share 98% of our genetic makeup with them. In the wild,

their courtship is perfunctory to say the least.

And females may be mated by one male after another. The act of copulation

lasts only a few seconds,
and the females appear remarkably

unmoved by the event.
Chimpanzees don't form lasting partnerships

and the males play little part in raising the young.

How is it that we humans are so different in this respect?

I'm on the record as describing human beings
as the sexiest primates alive.

Now when I said that, people felt I was being provocative,

but that wasn't the case.

I was making an accurate scientific statement.

There are some very specific ways in which human sexuality

differs from that of our animal relatives.

And the biggest differences are found in the human female.

For instance,

she doesn't advertise when she's fertile.

Indeed, she may not even know herself when she is. So she sexually

active all the time and we'll make love even when there's

no possibility of conception.

Whereas female primates only come on heat for brief periods,

the human female has no sexual season. Throughout most of

her monthly cycle,

she stays attractive to men and is prepared to mate.

Indeed, human females are capable of reproduction and remain sexually

appealing throughout the whole year.

Not only that, females are sexually responsive through most

of their pregnancy and can become sexually active again quite

soon after giving birth.
Indeed human females can stay sexually

active for a large part of their adult lives. Frequently for

more than half a century.
Human males experience a sexual

climax similar to that of other primates, but unusually,

the human female also experiences an intense orgasm.

The phases of human courtship and the sexual act itself are

all much longer, more elaborate

and more intense than in any other primate.

This extended sexuality isn't some sort of cultural decadence.

It's a basic biological characteristic of our species.

Why have we abandoned the 8-second mating act of the typical baboon.

Finding the answer to this question was the task.

I set myself back in the early 1970s when I began work on

my book

Intimate Behaviour.

I called it Intimate Behaviour because I wasn't just looking

at human sexuality,

I was looking at the whole subject of loving relationships.

Now, we all talk a lot about love,
but very few of us

stop to analyse it scientifically.
I suppose we feel if we do that,

we'll somehow destroy the magic.
But that's not the case.

In fact, the more we understand love,
the more fascinating

the subject becomes. But how does it all begin?

How does boy meet girl?

When children stop being toddlers and go to school,

something strange happens. All over the world
a major split now occurs

between the sexes.
Boys gather together in gangs. And girls

keep to themselves in all female groups. And the groups are

not really separate,

they're often actively hostile to one another.

This is an important step in sexual development.

In this pre sexual phase, young males
and females must become strangers

to one another so that, when puberty arrives, they can forge

an entirely new kind of relationship.
One in which undue familiarity

does not dull the excitement of discovery.

The all-male and all-female groups start to lose their mutual

hostility and replace it with mutual curiosity.

The new attachments are powerful,

but so too is the sense of belonging to one's old gang.

But sooner or later, the childhood gangs will lose this unequal

struggle for loyalty.

A new activity now arrives on the scene. Parading.

All over the world, young adults can be observed gathering together

in large informal groups.
On sea fronts, parks, High streets

or clubs.

The main preoccupation is simply making visual contact with

as many members of the opposite sex as possible.

Parading leads to a more direct
display of interest. This bolder eye

to eye contact is the first step

on the lengthy sequence of human courtship.

During this phase, primeval sexual influences are at work below

the surface. Careful research in certain nightclubs

has revealed that the closer girls are to their moment of ovulation,

the skimpier their costumes will be. Their display

of naked flesh is unconsciously dictated by their physiology.

For some young males, this visual phase of mate selection

becomes an exciting game to be relished and refined.

Here, it's skillfully played out on scooters in the streets of Rome.

In this purely visual stage of courting a mate,

decisions can be made in an instant, within the glance of an eye.

The brain has evaluated hundreds of pieces of visual information

and has made a judgment.

She's attractive or she's not.
He likes her or he does not.

Some of her signals

he will understand consciously.

Others, he'll be reacting to without even realising it.

So what are these sexual signals?

What does the human animal see as sexy?

Throughout the animal kingdom, males are attracted to females who

transmit signals of health and fertility. Positive signals

of potential childbearing and child-rearing.

The same is true for human males.

Even if breeding success is farthest from their minds when

they look at a passing female,
it still influences their feelings

towards her.

It's the same for human females.
When they look at males,

their ancient impulses encourage them
to seek out signs of masculine power

and strength, indications of protective prowess.

Although health and vigour are important displays for both sexes,

many human sexual signals are specific to one gender or the other.

Some of these gender signals are obvious enough, such as the

broader shoulders of the male or the narrower waist of the female.

The smooth skin and
soft roundedness of the female body,

and of course the high-pitched voice,
are juvenile qualities

making males feel protective.
The thick neck, facial hair, deep voice

and muscular torso of the male offer a strong visual

contrast saying I'm a protector.
Many male costumes exaggerate

these gender signals.
Male shoulders are widened by padded jackets,

or even further enlarged by adding epaulets,
or huge shoulder pads.

And sometimes by extraordinary ritualistic costumes

like these deliberately imposing uniforms of these Tibetan Monks.

Emancipated females who wish to be more assertive

in modern society mimic the broad torso look when they power dress.

For the fashion industry, manipulating all these visual signals,

improving our nature, becomes a matter of professional expertise.

What I'd like to do Phillip, I'd like to dilate

her pupils, to open them up more and to make her irises green

to change them from brown to green and clean

the whites of her eyes

so her eyes are going to stand out much more. We could put a mask

over the whole eye, lighting the eye out a little bit and

then put the green in. Yes, that's the green looks great.

By making the irises paler,

they contrast more with the black of the pupil.

So when the pupil itself is artificially enlarged, the impact

is even greater. Enlarged pupils are a normal reaction to sexual arousal.

So they are unconsciously appealing.

The whiteness of the whites of the eyes is associated with

youthful health and vigour.

So this is also exaggerated.

Now she has super eyes, but what about the rest of the face?

Let's, let's clean up first the little crease marks just here

on the edge of her lips.

Again, a flawless complexion indicates health and the inherent

sexuality of youthfulness.

That's why any small crease lines are so carefully removed.

I kind of like this colour here.

That would be good, more red.

Just bring out the muscular.

The lips are made slightly more red,
imitating the change

in colour that occurs during sexual arousal.

So if we now just do a colour correction

to bring all of the skin,

I'd like all her skin just to be a little richer

and the skin colour is warmed up a little

to create the impression of a healthy sexual glow.

That's perfect.

That's perfect.

We've got it.

So what I want to do here is to stretch her legs along quite

considerably maybe as much as 20% really we need to go through

the legs stretching the thigh bone and the shinbone more.

Less stretch on the feet and the knees so that we keep

it as realistic as possible while making it as languid and

as long as possible.

Exaggerated leg length is an important

sexual signal, especially in females.

This is because the legs grow longer in relation to the rest

of the body as puberty approaches.

So super long legs means super adultness,
and therefore super sexuality.

Tiny bit more.

Yeah, let's see a before and after. Yeah, that's great.

That's great.

That's long. Doesn't look too unrealistic and good proportions.

When people meet there are many ways in which

they can transmit sexual signals.
With a smile, of course.

And for long-haired individuals, the unconscious grooming

of the hair, which says in effect,

look I'm making myself more attractive, more appealing for you.

Then there's that human speciality made possible by

our naked skin, the blush. This blushing of the visible skin

as a social signal is superficially similar to the flushing that

occurs in the final stages of lovemaking. The blush starts

at one spot in the centre of each cheek and then spreads

to cover the whole of the face, the neck and even the upper torso.

To the male onlooker,

this skin change is strangely attractive because it

of its implied innocence. It has a virginal quality that appeals

to him.

The use of a so-called blusher in modern makeup, supposedly

to highlight the cheekbones, mimics the start of a blush and

inevitably acquires some of its appeal.

The rounded hemispherical breasts of the human female transmit

a powerful sexual signal unique to our species. Monkeys and apes

are completely flat chested when they're not giving

milk to their young. But the human female retains her swollen breasts

throughout her adult life.
Breasts may have a maternal function,

but their shape is purely sexual in significance.

This breast shape appears to have evolved

as a mimic of the rounded buttocks.

Most female primates' sexual signals occur

in the rump region, but in our species with its vertical body posture,

it was necessary to have a frontal display as well.

If you think that's far-fetched,
just look at these two cleavages

to see how similar the shapes are.

Great.

Milder sexual signals are also transmitted by the rounded

female shoulders, and the smooth rounded knees, again providing

visual echoes of the primeval buttock display.

Another form of self mimicry. The large female lips in both

shape and colour mimic the external genitals. When the labia

redden during sexual arousal, the lips also become swollen

and redder, a change artificially heightened by the application

of lipstick. A cultural exaggeration that's been employed

by women since the days of ancient Egypt.

When it comes to the basics of

sexual attraction,

we may be animals, but we can be very sophisticated animals.

We have a conscious perception of what is beautiful

and what is sexy, as well as a biological one.

And one culture's ideal of beauty can differ greatly from another's.

In the West for example, a slender figure is considered especially

attractive for females.

And a moderately muscular frame is preferred for males.

In contrast, among the Maasai of East Africa, an incredibly

slim figure which, to us, looks almost effeminate, is the epitome

of masculine beauty. This contrasts strikingly with the much

heavier body that spells beauty in many of the islands of

the South Pacific, where it applies to both males and females.

Wherever you look as you go around the globe, there are local

beauty standards that are sometimes strange to foreign eyes.

They're often too subtle to be appreciated by outsiders,

but of enormous importance within the societies concerned.

For instance among the Toga of Southern India, female hairiness

is especially appealing to men.
Even to the extent of heavy

female eyebrows.

But although beauty standards do vary around the world,

there are a few universals that apply to the whole human species.

The outline of the adult male body for instance.

To be sexually appealing, the male needs to have a triangle

formed by wide shoulders above a narrow waist.

To females, another important male signal, is a compact muscular behind.

Perhaps because of its sexual thrusting power.

Male muscularity in general is appealing.
But the dividing line between the

well-muscled and the muscle-bound is a fine one.

Because an over cultivated physique implies vanity.

By contrast, a flabby body lacks the key signals.

Another quality that has universal sex appeal, is youthfulness.

Sex drive and fecundity are at their highest levels among

the youngest adults. The male sex drive peaks at the age of 18,

and the females fecundity, at 22.

When a survey of sexual appeal was made in 190 different

societies around the world.

It was discovered that the most important feature common

to all cultures was a healthy body and a clear unblemished skin.

Beyond the eyeing up stage,

we come to the next phase of the human courtship sequence.

The pickup.

How do people break the ice?

Well a useful device is the cultivation of the lucky accident.

Some irrelevant completely non-sexual factor, like exercising

the dog is introduced into the equation.

The individuals involved are not actively seeking a partner,

that would be too obvious.

Instead, they're engaged in a common pursuit which just happens to

bring them together.

More formal meetings between young people offer an opportunity

to parade, eye up, display and pick up, all at the same time.

These young Maasai males show off their prowess by leaping up and down

in their vertical dance.

They're watched discerningly by the young girls of the village,

who, even at this tender age are already deeply involved in

the exciting business of mate selection.

The hair flick signals the interest of a male in a particular female.

All around the world new connections are being made.

New links are being forged, as friendly words take over from

shy glances.

We've arrived at the chatter.

This is the information exchange phase in which people find

out as much as possible about one another's backgrounds,

their likes and dislikes. This reciprocal

detective work may take some time,
but it's a vitally important

process when embarking on a long-term breeding partnership.

In this particular region of modern China, the young men and

women have a traditional way for overcoming the greatest

problem of the chat up, shyness.
Instead of simply mingling

and chatting.

They keep apart and sing their conversation
from one group to another.

They might sing about their personal skills

or bravery which can cause a lot of amusement.

The reply might be about property.

The number of tractors in their village for instance.

In the bars of Los Angeles, the chat up technique, like the

clothing, is much more casual. But it works well enough.

Here, contact has been made, and personal involvement

has begun. Now talking becomes the key activity.

Any inconsequential chatter keeps the conversation

going, while the opportunity is taken to slip in important questions.

What's the other's marital status?

What is his or her job?
In other words, apart from looks,

what extra benefits could each bring with them to a relationship.

Having received sufficient encouragement,

he can now move in closer, and is rewarded with the first bodily contact.

The problem now is to get rid of one of his new

companions, so that he can end up in a twosome.

But this time, he fails, and they both say goodbye.

Perhaps next time?
It's not easy finding the ideal partner

and there'll be many false starts before the blend is right, but

once it is, we see a whole new phase developing, characterised

surprisingly, by what appears to be a return to infancy.

Couples cuddle and caress one another,

call each other silly names,
talk in high-pitched voices and

even rock together in one another's arms.

This is the stage

we usually refer to as falling in love.

Dave loves Sue. Joe loves Kim.
Love. What is love?

Perhaps it's just a polite word for sex.
A romantic way of describing

sexual attraction. Well it isn't.
It's much more than that.

Love is a basic biological mechanism and it has a very specific function.

The first time we encounter love is as tiny babies.

This is the age of total security, protection and trust.

But even at this early stage, another urge is beginning to

express itself. The urge to strike out on one's own.

And the process of growing up is the process of this new

urge gradually asserting itself, as the need for maternal

protection grows weaker.

When the infant becomes a teenager, the urge for independence

gains the upper hand, and the bond between parent and child starts

to collapse. Eventually, in what turns out to be a more traumatic event

than either parent or teenager had expected, comes the

moment of first true separation.
Here, the first day at College

churns up the emotions as one long-term

love bond slips

into the past tense, and the prospects of a brand new one are

about to appear on the horizon.

It's an intriguing fact, that for a new couple, the first evening

out together usually involves food and drink. We tend to take this for granted,

but there may be a special, deeper reason.

It's almost as if, as with many bird species,
humans indulge in courtship feeding.

A hidden camera catches this couple at

the very start of just such a dinner date.
As the meal progresses,

their growing intimacy happens as we watch.

They start smiling and leaning forward, not taking their eyes off one another.

Now the first touch, leading to a gentle hand kiss.

And now, like two parents with small infants they each

spoon feed the other.

Finally, again like courting birds, a gift is offered.

The encounter comes to an end.
In this familiar event,

we are in reality seeing not only pseudo parental feeding,

but also the reenactment of a primeval exchange deeply embedded

in our species after a million years as hunter-gatherers.

Food sharing, which in primeval times was the very basis of

human society.

As the sexual attachment of the couple increases, we see

them displaying a variety of what a called tie signs.

These are forms of body contact that tell other people that

an exclusive pair is forming.

So while they reinforce the closeness of the couple,

they also serve to exclude us from that relationship.

There's the arm around the shoulder.

This is not yet particularly intimate, but there are other

tie signs that will show a gradually increasing mutual trust

between the couple. The arm around the waist.

The double embrace, and next in increasing intimacy, rather unexpectedly,

the contacts move up towards the head region. Because of the

sense organs there,

this is a highly protected area, available only to our most

trusted companions.

With the knee touch, the contacts begin to approach the most

intimate region of the body.

There are two particular aspects of human anatomy

that make us sexually very different from most other animals.

First,

we have near-naked skins, and we've used that nakedness to

gain an additional source of intimate stimulation.

Something denied to our hairier cousins.

There's another sexual difference between us
and our animal relatives.

All male monkeys and apes, and indeed

most male mammals have what is called an "os" penis.

This is a penis bone,

and this is one from inside the penis of a walrus.

And this tiny one here is from the penis of a hedgehog.

The function of this bone is to produce an instant erection

the moment that a male approaches a female sexually.

The loss of this bone

in the human male means that his female has to arouse

him strongly before he can penetrate her.

This means that human pre copulatory behaviour becomes much

longer and much more sensuous.

So sex in humans has evolved to be more than merely procreative.

By becoming increasingly pleasurable, less automatic,

it's more subtle and more complex.

And in its final stages, courtship becomes even more prolonged

and intensely erotic.

This is not some modern sophistication.
Evolution has programmed us

for this extended body intimacy. For this skin to skin contact.

Using it as a means of strengthening the attachment

of the male and the female for one another.

An attachment that will become biologically very important for them

in the new role they're about to play.

In animal behaviour terms, they've pair-bonded.

That's what love is. The formation of a lasting pair bond.

But what's its function? For true understanding of human sexuality,

we have to look at our children.
At the progeny that result

from the sexual act.

As with other monkeys and apes, our offspring, as we all know,

are nurtured inside the female body, but unlike other monkeys

and apes, human babies are totally helpless at birth.

The human baby now goes through 10, perhaps 15 or more years of being

dependent on its parents.

It's a task beyond the resources of a single parent.

Perhaps not in today's welfare state, but certainly in any primeval society.

So they have to be two and there has to be a biological

function to keep the couple together in the interests of the child,

and that mechanism is the pair bond. Nearly all societies

encourage some sort of official reinforcement of the pair bond.

Typically a wedding ceremony. Whether the wedding is highly

traditional, or more flamboyantly modern. Whether it's a protracted

event full of ancient rites.

Or merely, a drive-in quickie.

It always carries the same public message.

Namely we're an exclusive couple now. Hands off.

Even in an arranged marriage, where love has played no part so far.

This muslim man, who's never seen his bride before

his wedding day is saying to the world when he touches her hand,

from now on, we two are unavailable

for pair bonding with anyone else.

And so at last the final stage of the pair bonding process.

The sexual act itself. For those who have enjoyed the natural

process of falling in love,

it's the end of the long courtship sequence. And the mating act too,

is long and intense. Because in our species it's not

concerned merely with procreation, but with mutual sexual rewards.

The first tender caresses are made more exquisite

by the suddenly super sensitive skin.
The first of many physiological

changes that now take place. Lips becoming swollen and sensitive.

Eyes glistening as a film forms across their surface.

Pupils dilating to become huge dark pools.

Respiration increases dramatically as the body starts to

need quantities of oxygen for the vigourous physical actions involved.

The nostrils flare as the respiration rate increases

to nearly four times the normal speed. More and more air is

drawn into the body where the lungs begin to pump harder

and harder.

The heart beats faster as the body embarks on a wholesale redistribution of

the blood supply.

Inside the arteries, natural body chemicals have been released

that produce feelings of euphoria and elation.
Blood is pumped from the internal organs

through the arteries to the veins

and capillaries near the surface of the skin.

Sweat glands open, supplying copious perspiration as a cooling agent,

and also as a source of personal scent which unconsciously

stimulates the partner. The whole body becomes much hotter

to the touch and waves of heat can be seen escaping from

the skin and the open mouth.

A heat-sensitive camera reveals the developing pattern of

body heat. The red areas being the hotter ones.

They spread around the face. The soft erectile tissue on the

side of the nose, an erogenous zone.

The lips swollen with blood becoming increasingly hot to

the touch.

The earlobes, another erogenous zone, and eventually,

the whole of the head.

Lower down on the body,

it's possible to see the genital region of the female becoming

intensely heated as sexual arousal progresses and the labia

engorge with blood.

The female breast enlarges dramatically during sexual intercourse,

increasing its size by up to 25%. Blood is pumped

into erectile tissues faster than it can be pumped away.

The nipples swell and become extra sensitive, increasing in

height by as much as one centimetre.

The penis also become swollen and stiffly erect.

Doubling its normal length in the process.

The erect penis is a marvel of fluid mechanics.

The erection is caused by a rush of blood in, up to 60 times

the normal level, and a simultaneous reduction in blood flow out

that helps to maintain it.

At high intensities of arousal, a sex flush appears on the

female body and the shared experience of lovemaking is ultimately

to be reinforced by the orgasm. As the man's muscles spasm,

on his face is portrayed not pleasure,

but surprisingly pain, caused by the extreme physical intensity

of the moment. The male orgasm fulfills its biological function

to deliver a pool of ejaculate inside the vagina, as close

as possible to the cervical aperture.

With a mating act as intense as that, one might imagine that

the human pair bond would be safe for life.

But as we all know, this is not the case.

So what goes wrong?

One of the problems of modern life, is that it puts undue demands

on a breeding system that evolved to operate in small

tribal communities where males are only away from their females

for short periods of time.
Today, separations may be much longer.

The pair bond evolved to protect the husband and wife and

the offspring at just such times of conflicting emotion and vulnerability.

But the pair bond is not a perfect system.

Appealing members of the opposite sex may attract a roving eye,

causing repeated conflict of loyalty, even if only in

thought rather than deed.

In complex societies,

there's a temptation to experiment with new sexual experiences

and to stray from the narrow confines of a single pair bond.

Adultery and adulterers have been common throughout history.

The advantage to the male is clear enough.

He may be a caring husband and a good father, but he also

gains from scattering his genetic material over a wider range.

Through his additional offspring his genes will go marching on.

The risk he runs, is that if he's found out, he may damage

his pair bond and disrupt the rearing of his children.

When it's discovered, an adulterer is nearly always attacked

by society and feelings of guilt can become intense.

You are also accused I use the word accused because no one likes it.

of being a womanizer.

What do they mean by a womanizer?

They mean that I wasn't faithful, to my wife.

Was that true?

Yes.

Did you stop that?

Yes, I don't think it's something I want to talk a great

deal about.

Of course females may stray from the pair bond as well as males.

Among the Wodaabe Nomads in Niger,

this married man is meeting this married woman. In this tribe.

it's accepted as a woman's right that if she's not satisfied

with her own husband,

she can go off with someone else's.
In most societies, this pattern of behaviour

is strongly attacked. But its existence

suggests that their must be some genetic advantage for

an adulterous female, as well as for an adulterous male.

What could that be?

She can't scatter her genes

like an unfaithful male.

So what can she gain from it?

To understand this we must return to the moment of the orgasm.

When the male ejaculates, a sperm pool is deposited near to

the cervix, the entrance to the womb.
The female usually takes

a little longer to reach her orgasm.

But when she does, it's just as intense.

Her muscular contractions
spread through the genital region

to the cervix itself.
And seen here on film for the first time

these contractions help to dip the mouth of the uterus

repeatedly into the sperm pool.

And in this way, increase the chances of fertilisation.

It's now thought that by varying the timing of her orgasms,

the human female can increase or decrease her chances of

fertilisation by the sperm of any particular male.

If unfaithful, she could for instance favour the sperm of a

young healthy lover, while continuing to gain protection from

a powerful older husband.

Intriguingly her husband's sperm have their own secret answer to this.

It's what we might call sperm wars.
It's usually imagined that

all the millions of sperm deposited by the male are struggling

to fertilise the egg, but new research has proved that this

is not the case. Only a small proportion of them are actual

egg seekers. The rest have another task.
They ignore the egg,

because it's their job to fight a rearguard action, to destroy

any foreign sperm that may arrive on the scene.

There are two kinds of these protective sperm.

The first are active ones that search for and kill alien sperm,

but they have no interest in finding the egg.

New research suggests that a man can unconsciously control the numbers

of these killer sperm

in his ejaculate and that would depend on whether or

not he believed

he was the first or second male to mate with a particular woman.

Here's one in action.

This is chemical warfare, again filmed for the first time,

and when the two sperm separate one is left dead.

Other protective sperm are more passive.

These are the blockers. They swim little, but curl their tails are

interlock them. Massing together to form a barrier against invaders.

They will let later sperm from the same male pass but block

the way of sperm from other males.

It's a kind of internal chastity belt which presumably will

not have evolved without some promiscuity to counter

in the first place.

Drenched in a film of sweat, the lovers rest. Now mutually

rewarded through their shared orgasms. Inside the woman's body,

the sperm are active.

Some will be starting their marathon journey in search of an egg.

Others will be standing guard, needed or not.

Promiscuity is a high-risk strategy for the human-animal.

On balance, we're better off less stressed with our pair bonds.

Even today, 99% of humans live in a pair bond.

It's the fundamental condition of the human species.