The Scientific Basis of Attractiveness

Summary

In this insightful discussion, the focus is on the biological underpinnings of attractiveness, particularly bilateral symmetry's role in sexual selection. The conversation delves into the development of methods to measure facial symmetry and its significance as an indicator of developmental health and quality. It also explores the broader implications of physical attractiveness as a subconscious health certification and its impact on mating success, including the intriguing concept of cryptic female choice and its various manifestations in human behavior and other species.

Takeaways

• 🧬 Bilateral symmetry is a key trait in judging physical attractiveness in both humans and animals, serving as an indicator of developmental health.
• 🔍 The speaker and a colleague developed a method to measure facial symmetry in humans, which became a significant research topic in attractiveness studies.
• 🏞 Bilateral symmetry is important for reducing drag in movement, which is crucial for efficiency in forward-moving organisms.
• 🤔 Perfect bilateral symmetry is difficult to achieve, making it a marker of an individual's developmental quality.
• 🌟 Physical attractiveness is fundamentally a health certification, an unconscious assessment of traits important for health and developmental health.
• 👶 Research has shown that infants prefer to look at symmetrical faces, indicating an innate preference for symmetry in attractiveness.
• 👥 The speaker's research extended to the impact of symmetry on mating success, with more symmetric men reported to have more sexual partners.
• 🤝 The study of female orgasm in relation to sexual behavior suggests it may be part of female mate choice, influencing the fertilizing capacity of male ejaculate.
• 💡 Cryptic female choice involves subtle preferences that are invisible if only measuring classical male mating success, such as adjusting mating duration or the decision to lay eggs.
• 🔑 Female orgasm may serve as a mechanism for differential allocation of male ejaculate, favoring the sperm of certain partners over others.
• 🌐 The concept of cryptic female choice has broadened the understanding of female mate selection beyond simply choosing a partner, to include more nuanced behaviors.

Q & A

What is the significance of bilateral symmetry in the perception of attractiveness?

Bilateral symmetry is a marker of developmental health and quality of an individual. It indicates that the organism has developed without significant disruptions, which is seen as an attractive trait in potential mates across various species, including humans.

How does bilateral symmetry relate to movement efficiency?

Bilateral symmetry is important for reducing drag during movement. An organism with perfect bilateral symmetry moves more efficiently, as asymmetry can create resistance and reduce the effectiveness of motion.

What was the method developed in the early 90s to measure facial symmetry?

A method was developed to measure the symmetry of the two sides of the human face, which involved precise measurements that had not been successfully achieved in previous studies.

How does facial symmetry relate to the perception of attractiveness in different age groups and ethnicities?

Facial symmetry is a consistent marker of attractiveness across different age groups, from infants to the elderly, and among various ethnicities, indicating a universal preference for symmetrical faces.

What role does movement symmetry play in attractiveness?

Symmetry of movement contributes to the perception of attractiveness by indicating fluidity and grace, which are associated with good health and physical fitness.

How is physical attractiveness related to health certification?

Physical attractiveness is fundamentally a subconscious assessment of an individual's health and developmental status, with traits like bilateral symmetry serving as indicators of good health.

What was the outcome of the research on the relationship between facial symmetry and perceived attractiveness?

The research showed that there is a positive correlation between facial symmetry and how attractive a person's face is perceived to be by others.

How does body symmetry relate to mating success in men?

Men with higher body symmetry, indicating better developmental health, are found to be more physically attractive and have more sexual partners, which is a measure of mating success.

What is the concept of cryptic female choice in the context of sexual behavior?

Cryptic female choice refers to the subtle ways in which females can influence the fertilizing capacity of sperm from different males, such as through orgasm, which can pull ejaculate closer to the cervix for better fertilization chances.

What is the evolutionary purpose of female orgasm according to the script?

Female orgasm may serve as a mechanism for cryptic female choice, where the uterine contractions during orgasm can help to pull the male's ejaculate closer to the cervix, potentially increasing the chances of fertilization.

How does the concept of cryptic female choice extend to other species, such as scorpion flies?

In scorpion flies, cryptic female choice is observed through behaviors like adjusting mating duration to receive more sperm from larger, higher-quality males, and making decisions about egg fertilization based on the last male they mated with.

Outlines

00:00

🔍 Perception of Attractiveness and Bilateral Symmetry

This paragraph discusses the speaker's research on the perception of attractiveness, focusing on the role of bilateral symmetry in determining physical attractiveness. The speaker explains that symmetry is a marker of developmental health and is valued by animals, including humans, as a sign of a healthy mate. The research found that facial symmetry can be measured effectively and is related to attractiveness. The speaker also touches on the broader implications of symmetry in movement and its impact on health and attractiveness.

05:01

👶 Infant Preference for Symmetrical Faces

In this paragraph, the speaker delves into the preferences of infants for symmetrical faces, highlighting that research has shown infants tend to look longer at symmetrical faces, indicating a natural preference. The discussion extends to the broader impact of facial symmetry on attractiveness across different age groups and the role of symmetry in everyday life, including its correlation with mating success and sexual behavior. The speaker mentions further studies on body symmetry and its connection to attractiveness and sexual partners.

10:03

🌟 Female Orgasm and Mate Choice

The speaker explores the evolutionary purpose of the female orgasm, suggesting it may be part of female mate choice rather than a direct adaptation for pregnancy. The paragraph explains that orgasms in females can facilitate the movement of ejaculate towards the cervix, potentially influencing the fertilizing capacity of sperm from different partners. This concept is linked to the idea of 'cryptic female choice,' where females may unconsciously prefer the sperm of certain males, thus affecting the genetic quality of their offspring.

15:03

🦂 Cryptic Female Choice in Insects

The final paragraph shifts the focus to the concept of cryptic female choice in insects, specifically scorpion flies. The speaker describes how females in these species adjust mating duration based on male body size, favoring larger, fitter males by receiving more sperm from them. Additionally, the speaker discusses how females make post-mating decisions about egg-laying, which can also influence the use of sperm from specific males, thus demonstrating a form of cryptic choice that is not immediately apparent from traditional measures of mating success.

Keywords

💡Attractiveness

Attractiveness in the context of the video refers to the physical appeal of an individual, which is influenced by factors such as facial and body symmetry. It is a key theme as it is discussed in relation to sexual selection and mate choice, with the script mentioning that humans and other animals use symmetry as an indicator of health and genetic quality.

💡Bilateral Symmetry

Bilateral symmetry is a concept that describes the balanced and mirror-image characteristics of an organism's body. In the video, it is highlighted as a marker for attractiveness and developmental health, with the script discussing a method developed to measure facial symmetry and its correlation with perceived attractiveness.

💡Sexual Selection

Sexual selection is an evolutionary process where certain traits are favored because they increase an individual's chances of attracting mates and reproducing. The video discusses how traits like bilateral symmetry are preferred in sexual selection due to their association with health and genetic quality.

💡Developmental Health

Developmental health in the script refers to the well-being and proper growth of an organism. Bilateral symmetry is used as an indicator of developmental health because perfect symmetry is difficult to achieve and thus signifies a high-quality individual, as explained in the video.

💡Mating Success

Mating success is a measure of an individual's reproductive success, often quantified by the number of sexual partners an individual has had. The video script discusses how more symmetric men have higher mating success, indicating a link between physical symmetry and reproductive outcomes.

💡Cryptic Female Choice

Cryptic female choice is a concept where females exert subtle influence over the reproductive process, such as choosing which male's sperm to use for fertilization. The video describes this as a form of female mate choice that is not immediately apparent but can significantly impact the genetic makeup of offspring.

💡Orgasm

In the context of the video, orgasm is discussed as a potential mechanism in female mate choice. It is suggested that the act of a female having an orgasm can facilitate the movement of a male's ejaculate towards the cervix, potentially increasing the chances of fertilization with a preferred partner.

💡Infidelity

Infidelity within the video is mentioned in the context of more symmetric men engaging in more extra-pair mating. It is suggested that this behavior is part of their mating success strategy, indicating a link between physical traits and mating behavior.

💡Sire Choice

Sire choice refers to the preference a female may have for a particular male's genetic material when choosing a partner for reproduction. The video script discusses how cryptic female choice can manifest as a preference for the sperm of certain males over others, based on factors like symmetry.

💡Evolutionary Purpose

The evolutionary purpose of certain traits or behaviors, such as female orgasm, is discussed in the video. It suggests that behaviors may have evolved to increase reproductive success, such as by facilitating fertilization or signaling genetic quality.

💡Genetic Quality

Genetic quality is the concept of an individual possessing desirable genetic traits that can be passed on to offspring. The video script suggests that females may seek high genetic quality partners to ensure the health and survival of their offspring.

Highlights

Research on the perception of attractiveness, focusing on bilateral symmetry and averageness in relation to sexual selection.

Development of a method to measure facial symmetry in humans as an indicator of developmental health and attractiveness.

Bilateral symmetry's role in reducing drag for forward-moving organisms, contributing to its importance in mate selection.

The difficulty in achieving perfect bilateral symmetry as a marker of an individual's developmental quality.

The preference for bilaterally symmetrical designs in human-made objects like cars and airplanes.

The correlation between facial symmetry and perceived attractiveness in various studies.

Infants' preference for symmetrical faces as demonstrated through attention span in research.

The extension of symmetry research to include movement and its fluidity as an aspect of attractiveness.

Physical attractiveness as an unconscious health certification based on evolutionary traits.

The relationship between a man's facial and body symmetry and his reported number of sexual partners, indicating mating success.

The connection between a man's symmetry and his likelihood of engaging in infidelity.

A study on female orgasm patterns during mating and their correlation with male reports, indicating attention to female arousal.

The hypothesis that female orgasm may serve as a cryptic choice mechanism, influencing fertilization potential.

The concept of cryptic female choice, where females may prefer the sperm of certain males over others.

Examples of cryptic female choice in insects, such as scorpion flies, adjusting mating duration based on male body size.

The broader implications of cryptic female choice for understanding female mate selection and offspring quality.

Transcripts

you so I've come across your research a

number of times in my career struck by

its uh its originality and and its

impact I I'd like to ask you first about

something I I probably ran into maybe

it's 20 years ago maybe it's 15

something like that you did some work on

the perception of attractiveness

bilateral symmetry averageness and

sexual selection can you outline what

you found and

why yes um I did work um some years ago

now in uh uh human uh attractiveness and

um that turned out to to be very uh

productive about attractiveness in

general in animals and one of the key uh

traits that animals look at in judging

uh physical

attractiveness of of Partners of Mates

is a bilateral symmetry and uh a

colleague and I in the early 90s uh came

up with a way to measure uh facial

symmetry in humans it had been U worked

on before and but the measurements that

they used were uh didn't work uh so we

came up with a with a method that did

work measuring bilateral symmetry in the

face so that is a symmetry of the two

sides of the face why is that important

and why is it a marker for

attractiveness it turns out that that

bilateral symm is a measure of

Developmental health and so the the

organism uh when it starts developing

it's designed by evolution by selection

to to uh achieve a bilaterally symmetric

form you can think of that this is the

case when I say organisms I mean all

forward moving organisms all forward

moving

organisms uh have uh have have

adaptations developmental adaptations to

achieve a bilaterally symmetric body

because first of all that reduces drag

so if you're moving

forward and you're bilaterally symmetric

you don't have any drag in your movement

you can think about a person with a a

leg uh a bit shorter than the other and

there's drag in the move in the forward

movement the more of that asymmetry the

more drag so you lose efficiency in

movement

that's fundamental to what bilateral

symmetry is about but next bilateral

symmetry is very hard perfect bilateral

symmetry is very hard to achieve by

development so it's a marker of quality

of the individual pertaining to its

developmental Health we see in many

things that human beings design to move

forward bilateral symmetry cars are

automobiles are bilaterally symmetrical

airplanes are bilaterally symmetrical so

we like our world to be that way yeah we

like to be that way actually it turns

out and you're associating it with

principle if you had if you had one side

of the car uh asymmetric compared to the

other side of the car then there'd be

more drag you know it's not an offish

you you'd use more gas think about it

that way uh in driving down the road

with an asymmetric car um but so this

this is one component of physical

attractiveness bilateral symmetry and we

looked first when we developed this uh

way to measure facial symmetry uh that

became a a a very hot research topic we

did the first and then others followed

very quickly and lots and lots of

research has been done now but there's

you know symmetry of movement that's

important in in how fluid one's movement

is and how attractive therefore for one

this movement is you're not dragging

your foot or whatever and um all that is

really a a

component of the importance of Health in

physical attractiveness So Physical

attractiveness fundamentally is a health

certification that's how we judge uh

people's attractiveness we don't think

about it consciously it's an unconscious

calculation of the traits important in

uh health and developmental Health as

bilateral symmetry is one of these so

you measure the symmetry of the two

sides of the face and we showed in our

first study of this way back now that um

that measurement uh relates to how

attractive faces are perceived faces of

the same sex or opposite sex and then

that research went on to look at uh kids

looking at faces and uh different ethnic

groups looking at faces it works like a

charm wherever you do it lots and lots

of research and so does it mean that if

you show people symmetrical or

asymmetrical faces that they obviously

have a preference for the symmetrical

faces will they look longer at the

symmetrical faces will infants look

longer at symmetrical faces yes they do

yeah that's the way the infant infant

Beauty research is done you just look at

whether the whether the bab and they got

it down now to almost newborns you know

looking at

faces and um judging these faces

basically on the basis of how long they

look at the face versus getting

distracted to something else and

symmetry is one compart part of the uh

Beauty whether you're talking about

babies or kids or old people or young

people or whatever facial symmetry is is

very important it's not the only Beauty

marker in the face we look at we can

talk about that in a moment too because

that gets us into uh some other research

we've done but symmetry is a very

important one now that research went on

to look at how symmetry plays out in the

everyday lives of people and we did uh

the initial studies on that but again

that that research bloomed and uh lots

of people have have done it and still

it's an active part of research but the

first thing we did not just

attractiveness we did a bunch of that in

relation to symmetry but we looked at U

sex lives of uh people romantically

paired people uh studies of uh couples

and um looked at uh looked at uh uh

reports by men and women of sex partner

number that they've had in their

lifetime that was one component of

because that's that's a that's a measure

in Men in particular of uh what

biologists call mating success so number

of number of uh sexual partners one has

and uh that that research showed that

for in the more symmetric the man uh the

more sex partners he had and a technical

detail there after we we you know

initially started with facial symmetry

but then we moved to the body of people

we came up with a metric for body

symmetry measuring 11 traits on both

sides of the body these traits are um

ear length and ear

width um and

and then we measure elbow there's some

elbow anatomy there that we measure some

bones wrists fingers all those then

measure of course on both sides measure

foot width ankle width Trace like that

and we put that together in a composite

as a measure of body bilateral symmetry

that correlates highly with facial

symmetry because the Symmetry is a

developmental Health measure throughout

the body and um that Cor relates with

mating success of men more more

symmetric men are physically more

attractive and they have more sex

partners uh we also got into um looking

at Men's infidelities in Mar

relationships and found that more

symmetric men uh engage in more uh

meetings outside the parabond as well so

that's that's part of their mating

success we did uh the first study of um

uh kind of modern study we would call it

of female

orgasm uh in Rel in in in uh copulatory

orgasm uh so in part looking at women uh

200 romantically paired couples and

asking the women about their orgasm

patterns during mating with their

partner and separately asking the men

and we found that the men's reports and

the women's reports a frequency of

ulatory orgasm by the women were very

highly correlated so men are paying

attention to this phenomenon of whether

the female is sexually aroused to the

Zenith level of orgasm of course and

more symmetric men were firing uh more

copulatory orgasms too that was a very

classic study in human I have a specific

question about that I've always wanted

to ask a biologist interest in sexual

behavior but I know that there's been a

lot of discussion about the hypothetical

evolutionary purpose of female orgasm

and I was wondering if female orgasm is

disproportionately likely to trigger

trigger male

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orgasm because it could be it could be

an adaptation that's used to elicit

pregnancy essentially yeah I don't think

it is it's there's no there's there's no

evidence that

females that orgasm very

infrequently have fewer babies

and actually women who don't ever orgasm

can be quite fertile so I don't think

it's fundamentally that I think what it

is is it's part of female mate choice

and more and more basically sire choice

of the female let me

explain so when a female uh has an

orgasm uh she has uterine contraction of

course and that pull it works like a

suction it pulls the uh content

of the vagina up to the cervix so it

puts the puts the content of the vagina

in a good place and if that content

includes the male's ejaculate and she's

pulling the male's ejaculate up to the

cervix where it's easier for him to get

you know either for the Jack ejaculate

to get into the right place to conceive

so if she imagine a female who has two

mating Partners she orgasms with one

pulling his Ed it up to the cervix and

she skips orgasm with the other partner

so she in effect is mated with both men

so that is you know same mating success

of the two men if you just look at

mating success but she's doing something

more

subtle that is differentially affecting

the fertilizing capacity of the

ejaculate of the two men the men the

jacket she pulls up has more potential

for fertilization and that's a component

of cryptic female choice so uh in the

80s I discovered uh what I labeled as

cryptic female Choice first in insects

and then uh it it applied to uh female

orgasm uh too in in humans as cryptic

female choices is just the the kind of

female choice that is invisible if

you're only measuring mating success so

in the example we talked about the two

guys mating with this female had the

same mating success they both mated with

her but one had was was preferred over

the other by the female's orgasmic

capacity with him that pulled his e

jacket it up and so females by showing

this differential uh um orgasm pattern

that I described with symmetry are

favoring symmetric Partners over other

men

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15th and hypothetically healthier

partners and and hypothetically

providing their kids with with an

advantage that's right higher genetic

quality and then that's that's an issue

behind all this discussion so far is

that uh female organisms uh are

after um High gen Quality Partners when

when they're you know to be fathers of

their offspring so it's a sire Choice

more the a cryptic female choice is more

of a sire Choice than just a mate choice

and darwinian dar Darwin Charles Darwin

discovered female choice and did a lot

with it for sure and biologists had

viewed um female choice in a darwinian

framework up until very recently until

cryptic female Choice came along but

female are far more sophisticated than

just choosing one male over another as a

mate they do they do these subtle things

and involved in cryptic choice to prefer

some the uh sperm of some mates over the

sperm of others whole site of now that's

a big area of well what other elements

are what other elements make up cryptic

choice you you describe the orgasm what

else what else first discovery was was

in some insects called scorpion flies

and what the females do there is they

adjust mating

duration and hence the amount of

ejaculate that the male transfers

there's no orgasm in these insects but

the longer the male can mate the long

the bigger his the the more sperm he

transfers to the female so females are

adjusting ejaculate duration on the base

of body size of the male so and but

bigger males are more fit males and so

forth better growth and more resource is

growing up they're higher quality males

the females are receiving more sperm

from bigger males that's one thing I did

with these insects another was the

female after she mates with a male makes

a choice of whether to lay eggs or not

if she chooses to lay eggs then she will

fertilize we know from other research

I've done she will fertilize those eggs

with the last male sperm she made it

with so if she makes the decision leg

egg she's going to use that M last male

sperm sheet and and large males again um

are preferred in that component of

cryptic female choice so cryptically

these female scorpion files are

preferring large-bodied males by both uh

receiving more sperm from them and

making decisions to lay eggs uh with

them and not other males so those kind

of subtle things that uh females do that

aren't apparent if you're just measuring

classical

male mating success you know

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