Human Variation

Sexual Dimorphism

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KIN-ScaleProportionality Profile

KIN-Scale data composed of data from Kin 303 students 2004-2011.

Means and SEMs of z-values for KIN-Scale Males (n=230) and Females (n=336)

Visual test of significance allows for a lot of information to be portrayed in one figure

Sexual Dimorphism in KIN-Scale subjects

No difference in proportional weight

Male-Female difference greatest in: Triceps, Biceps, Front Thigh and Medial Calf Skinfolds Secondary sexual adiposity

Sexual Dimorphism in KIN-Scale subjects

Representative Measures

Muscle Mass Muscle X-sectional Area Skinfold-Adjusted Arm Girth – Muscularity Indicator

G

Ga = G - (3.14xS)

S = Skinfold ThicknessG = GirthGa = Skinfold adjusted Girth

Ga

SG

Girth adjusted for Skinfold at that site

Girth Skinfold

s.a. Arm girth Relaxed Arm Girth Triceps

s.a. Chest girth Chest Subscapular

s.a. Thigh girth Thigh Front Thigh

s.a. Calf girth Calf Medial Calf

s.a. Forearm girth Maximum Forearm Forearm

s.a. Girth (cm) = Girth (cm) - (Π x Skinfold (mm) / 10)

Sexual Dimorphism in KIN-Scale subjects

s.a. Girths are Muscularity indicators

Greatest differences between the sexes in the upper body

Greatest potential for hypertrophy in the upper body

Muscularity profile is very sensitive to the specific activity of the individual

Sexual Dimorphism in KIN-Scale subjects

Proportionally larger sitting height in females

Males tend to have proportionally longer limbs.

Biggest difference in distal segments

Sexual Dimorphism in KIN-Scale subjects

Humerus to Femur Width differences reflects muscularity differences

Males have broader and deeper chests proportionally.

Classic hip-shoulder dimorphism:

Males proportionally wider shoulders

Females have proportionally wider hips

Shoulder-Hip Dimorphism

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  Sex N MeanStd.

Deviation

Biacromial/Biiliocristal Breadth Male 69 1.44 0.12

  Female 115 1.31 0.12

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2D:4D Ratio(2nd digit length to 4th digit length ratio)

Sex N Mean Std. Deviation

Male 136 0.947 0.029

Female 137 0.965 0.026

2D 4D

a Allison A. Bailey, Peter L. Hurda, Department of Psychology, University of Alberta. 2004

2D:4D Ratio

Ratio determined in utero 2D:4D is negatively correlated with prenatal testosterone and

positively correlated with prenatal estrogen

Larger ratio in females Married women had higher 2D:4D ratios than unmarried women Significant negative associations were found between 2D:4D in

men and reproductive success and significant positive relationships between 2D:4D in women and reproductive success

Found to be related to: Aggression Competitive success Sexual orientation

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Histogram of Both Sexes Combined

Sex N Mean S.D.

Male 76 0.975 0.037 Female 66 0.994 0.043

Ethnicity and Race

Ethnic group a socially defined category of people who

identify with each other based on common ancestral, social, cultural or national experience.

Race a group of people identified as distinct from

other groups because of supposed physical or genetic traits shared by the group.

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Racial/Ethnic and Individual Differences

Chinese South Asian European

MANUS – Papua New Guinea

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Most naturally mesomorphic group yet measured with Heath-Carter somatotype

DINKA - Sudan

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Most naturally ectomorphic group yet measured with Heath-Carter somatotype

Manute Bol (7’ 7” Dinka)

Spud Web (5’ 7” African-American)

Both former NBA players