FromFrom DarwinDarwin ExamplesExamples ofof ArbitraryArbitrary CulturalCultural StandardsStandards ArbitraryArbitrary CulturalCultural StandardsStandards ArbitraryArbitrary CulturalCultural StandardsStandards BeautyBeauty isis inin thethe eyeeye ofof thethe beholder,beholder, oror isis it?it? ►►TheThe standardstandard claimclaim isis thatthat conceptionsconceptions ofof beautybeauty areare culturallyculturally determineddetermined andand thereforetherefore arbitrary.arbitrary. ►►ResearchResearch overover thethe lastlast dozendozen yearsyears oror soso revealsreveals thatthat howhow wewe evaluateevaluate beautybeauty inin thethe humanhuman bodybody appearsappears toto bebe basedbased onon aa universaluniversal setset ofof standards.standards. Therefore,Therefore, somesome conceptionsconceptions ofof beautybeauty areare notnot culturallyculturally determined.determined. WhatWhat isis Beautiful?Beautiful? RelativeRelative andand AbsoluteAbsolute StandardsStandards inin AttractivenessAttractiveness

► UniversalUniversal model:model: holdsholds thatthat therethere areare absoluteabsolute standardsstandards thatthat peoplepeople useuse toto assessassess attractivenessattractiveness ► AssortativeAssortative modelmodel (like(like attractedattracted toto like):like): holdsholds thatthat standardsstandards areare relativerelative toto thethe viewer.viewer. ThatThat is,is, wewe areare attractedattracted toto thosethose whowho areare similarsimilar toto us.us. AlsoAlso knownknown asas positivepositive assortativeassortative mating.mating. ► WeWe willwill beginbegin withwith thethe universaluniversal (or(or absolute)absolute) andand followfollow withwith thethe assortativeassortative (or(or relative)relative) BasesBases forfor femalefemale physicalphysical attractivenessattractiveness ¾General ƒSymmetry: low fluctuating asymmetry (applies to males also) ¾Body form ƒWaist to hip ratio of approximately 0.7 (?) ¾Face ƒAverage (applies to males also) ƒsmall lower jaw (nasion to chin) ƒhigh upper and lower lips ƒsmall mouth (width) ƒlarge eyes ƒlight skin ƒhomogenous skin texture SymmetrySymmetry HowHow symmetrysymmetry isis measuredmeasured SymmetrySymmetry measures:measures: 11 SymmetrySymmetry measures:measures: 22 SymmetrySymmetry measures:measures: 33 SymmetrySymmetry measures:measures: 44 SymmetrySymmetry measures:measures: ““What?What? MeMe Worry?Worry?”” PhysicalPhysical developmentdevelopment andand symmetrysymmetry areare regulatedregulated by:by: ƒgrowth rates ƒhormone levels ƒnutrition ƒdisease 9The level of symmetry is a measure of developmental stability. 9Developmental stability is an indication of an individual's ability to withstand genetic and environmental stress during growth. 9High FA is associated with increased morbidity and decreased heterozygosity SymmetrySymmetry isis positivelypositively associatedassociated withwith ► StatureStature ƒ Tall males less asymmetrical (positive association) ƒ Small females less asymmetrical (negative association) ► IQIQ ► NumberNumber ofof lifetimelifetime partnerspartners andand RSRS (males(males && females)females) ► DiseaseDisease resistanceresistance ► RunningRunning speedspeed ► AggressionAggression ► DepressionDepression Behavior

Source: JT Manning et al., 2002, Evolution and Human FacialFacial AveragenessAverageness Examples:Examples: facialfacial averagenessaverageness (Asian)(Asian) CreatingCreating aa facialfacial averageaverage (N.(N. Amer.)Amer.) AverageAverage plusplus reducereduce jawjaw andand peakedpeaked lipslips AveragenessAverageness isis associatedassociated withwith

high levels of heterozygosity which, in turn, is associated with enhanced pathogen resistance. That is, average looking people tend to be healthier. MaleMale AttractivenessAttractiveness andand SpecificSpecific FacialFacial FeaturesFeatures ►►ProminentProminent cheekcheek bonesbones andand longerlonger lowerlower facesfaces areare bothboth judgedjudged asas attractiveattractive inin males.males. ►►WhenWhen thesethese twotwo factorsfactors areare combinedcombined aa masculinitymasculinity indexindex isis created,created, andand thisthis indexindex isis moremore stronglystrongly correlatedcorrelated withwith attractivenessattractiveness thanthan cheekbonecheekbone oror longerlonger lowerlower faceface alone.alone. ►►Finally,Finally, malemale facialfacial symmetrysymmetry andand thethe masculinitymasculinity indexindex werewere correlated.correlated.

Source: Scheib, Gangstead, and Thornhill “Facial attractiveness, symmetry and cues of good genes. Proc. R. Soc Lond. B (1999) FeminineFeminine andand MasculineMasculine FacesFaces

►►MalesMales favorfavor womenwomen withwith femininefeminine facesfaces ƒƒ SmallSmall chinchin andand highhigh cheekcheek bonesbones ƒƒ FullerFuller andand moremore peakedpeaked lipslips ƒƒ LargeLarge eyeseyes (relative(relative toto face)face) ►►FemalesFemales seemseem toto favorfavor malesmales whowho areare slightlyslightly toto moderatelymoderately faciallyfacially masculinemasculine butbut notenote extremelyextremely soso ƒƒ ChinsChins broaderbroader andand longerlonger ƒƒ LargeLarge browbrow ridgeridge WaistWaist toto hiphip ratiosratios

WHR is a reliable index of age, hormonal status, parity, fecundity, and health. Before puberty boys and girls have similar ratios. However, with females pelvis widens and fat is deposited on hips and thighs at puberty. Healthy women have ratios of 0.67 to 0.80 while healthy men have 0.80 to 0.95. For attractiveness, ideal for men is 0.90 and female ideal is 0.7 (for Western populations only). WaistWaist toto HipHip Ratio:Ratio: standardstandard stimulusstimulus setset WHRWHR andand femalefemale matemate valuevalue

WHR increases with each pregnancy and increases slightly with age. However, a 17 year old will have nearly the same WHR as a 22 year woman and at menopause it reaches the level of a male's WHR (about 1). High WHR is strongly negatively associated with the probability of conception and positively associated with age. WHRWHR ratioratio andand healthhealth correlatescorrelates

High WHR in women is a sign of: • menstrual irregularity • Hirsutism (abnormal growth & distribution of hair) • elevated plasma triglycerides • diabetes and insulin intolerance • hypertension •stroke • gall bladder disease • reproductive cancers (endometrial, ovarian, and breast) WHRWHR andand BehavioralBehavioral CorrelatesCorrelates inin WomenWomen

►►PositivelyPositively correlatedcorrelated withwith ageage ofof firstfirst intercourse.intercourse. ►►NegativelyNegatively correlatedcorrelated withwith numbernumber ofof lifelife-- timetime sexualsexual partnerspartners andand EPCEPC’’s,s, Examples:Examples: 0.70.7 WHRWHR (the(the moremore thingsthings change,change, thethe moremore theythey staystay thethe same)same) FurtherFurther exampleexample ofof WHRWHR’’ss WHRWHR ofof 0.70.7 aa reflectionreflection ofof WesternWestern standards?standards? ► Recent research by anthropologists reveals that a WHR ratio of about 0.8 is preferred in the following ethnic groups: ƒ Hadza ƒ Shuar ƒ Machiguenga ► This is greater than the 0.7 ratio reported in the west. ► May be a consequence of living in a food short and/or high pathogen environment which suggests that men are concerned with energy status when it is relevant (i.e., not relevant in the West but relevant in tribal populations) ► What about BMI? Additional research in the West suggests that BMI is more important than WHR. The problem with BMI and WHR is that they are strongly correlated with each other. Therefore it is difficult to determine which is the factor that influences perceptions of attractiveness in human body form. BMI/WHRBMI/WHR Brits & SA Zulus andand CultureCulture

“Changing perceptions of Brit Zulu & attractiveness as SA Zulus observers are exposed to a different culture” B. Martin J. Toveé et al. Evolution and Human Behavior(2006)

Brits of African Origin & Brit Zulus LocalLocal ConditionsConditions forfor SASA Zulus:Zulus: factorsfactors underlyingunderlying preferencepreference forfor aa highhigh BMIBMI Poverty & Hunger: People in rural South Africa are living in a low-resource, economically deprived society. Fifty-six percent report going hungry, and most households do not have electricity, running water, or significant amounts of household durable goods. In South Africa a higher female body weight is perceived to reflect affluence, high status, and good health. It is therefore not surprising that our results suggest that a higher female BMI is regarded as attractive. Health Problems: These preferences may be reinforced by the current health problems prevalent in South Africa. There are long-standing problems with infectious diseases, including lower respiratory tract infections, meningitis, diarrhea, septicemia and TB, which, when combined with low levels of immunization, make potential infection a serious possibility. The health consequences linked to these serious diseases include weight loss, and this is reflected in the perception that a lower body mass may signal potential parasitic infection or disease. ConclusionsConclusions ofof BritishBritish andand ZuluZulu StudyStudy

►►BritsBrits havehave aa preferencepreference forfor lowerlower BMIBMI thanthan SouthSouth AfricanAfrican ZulusZulus ►►WhenWhen SASA ZulusZulus areare rearedreared inin BritainBritain theirtheir preferencespreferences forfor BMIBMI movemove fromfrom thatthat ofof nativenative SASA ZulusZulus towardtoward nativenative BritsBrits ►►ItIt seemsseems toto bebe thethe casecase thatthat BMIBMI preferencespreferences areare influencedinfluenced byby toto dietarydietary andand healthhealth issuesissues andand culture.culture. AA finalfinal malemale attributeattribute SHR:SHR: shouldershoulder toto hiphip ratioratio anan introductionintroduction toto aa malemale signsign ofof fitnessfitness ►►Measurement:Measurement: ƒƒ hiphip measuredmeasured asas largestlargest circumferencecircumference aroundaround thethe hipships andand buttocks.buttocks. ƒƒ shouldershoulder measuredmeasured asas greatestgreatest widthwidth ofof shouldshould bladesblades withwith armsarms atat sides.sides. ►►Results:Results: ƒƒ menmen rangedranged fromfrom 1.031.03 -- 1.40,1.40, meanmean ofof 1.181.18 ƒƒ womenwomen rangedranged fromfrom 0.90.9 -- 1.22,1.22, meanmean ofof 1.031.03

SHR 1 of 2 SHRSHR inin men:men: behavioralbehavioral correlatescorrelates

►►NegativelyNegatively correlatedcorrelated withwith ageage atat firstfirst sexualsexual intercourseintercourse (narrow(narrow shoulders=latershoulders=later firstfirst sex)sex) ►►PositivelyPositively correlatedcorrelated with:with: ƒƒ reportedreported numbernumber ofof sexualsexual partnerspartners ƒƒ EPCEPC (extra(extra pairpair copulations)copulations) oror cheatingcheating onon youryour ownown partnerpartner (broad(broad shoulders=moreshoulders=more infidelity)infidelity) ƒƒ AttractivenessAttractiveness ratingsratings byby womenwomen

SHR 2 of 2 HeightHeight andand AttractivenessAttractiveness

► InIn thethe westwest malesmales preferprefer femalesfemales whowho areare shortershorter thanthan averageaverage whilewhile femalesfemales preferprefer malesmales whowho areare tallertaller thanthan average.average. ► Correspondingly,Correspondingly, talltall menmen havehave higherhigher RSRS thanthan shortershorter malesmales andand shortershorter femalesfemales havehave higherhigher RSRS thanthan tallertaller females.females. ► InIn ruralrural GambiaGambia thisthis relationshiprelationship seemsseems notnot toto hold.hold. ƒ Tall women had higher fertility & higher survivorship of their children ƒ While taller men were only very slightly more likely to have higher RS than shorter men

Sear “Height and Reproductive Success”. Human Nature 17(4) 2006. AssortativeAssortative oror relativerelative models:models: ““LikeLike seekingseeking likelike””

► People marry those who resemble themselves ► Known as positive assortative mating ► Couples correlate or resemble each other for most traits (height, weight, personality, social attributes, hair color, etc.) ► Presumably, this optimizes outbreeding to avoid excessive genetic variance that would interfere with coadaptive gene complexes ► You can’t always get what you want: while people who have greater symmetry, etc are more attractive, people tend to marry those who are physically most like them. ConclusionConclusion

► ThereThere areare universaluniversal standardsstandards ofof beautybeauty whichwhich include:include: ƒ Symmetry, WHR (or perhaps BMI), averageness, SHR, etc ƒ These are measures of health and other factors associated with fitness ƒ They also may vary with environmental factors (e.g., BMI preferences in Zulus and Brits) ► AtAt thethe samesame timetime likelike tendtend toto marrymarry likelike (positive(positive assortativeassortative mating)mating) ► BothBoth factorsfactors affectaffect humanhuman matemate choicechoice