Sex Determination

Question 1

Define:
Sex
Gender

Answer 1

Sex = The biological genotype (the genetic material)
          The phenotype (the physical form)
          Can be determined from the human skeleton

Gender = An individual’s self-conception: male or female?
Can’t be determined from the skeleton

Question 2

Define Sexual Dimorphism

Answer 2

• Distinct difference in size or appearance between the
  sexes in addition to the sexual organs themselves.
• There are 25 sex-determination characteristics

Question 3

Skeletal Consequences of Sexual Dimorphism

Answer 3

SIZE:
- Adult males = Larger joint surfaces, greater muscle bulk,
Stronger muscle attachments
- In general men have bigger attachment sites

REPRODUCTION:
- Females = hip bones and sacrum adapted for child birth,
and occasional show parturition scars

BIOCHEMISTRY:
- Sex differences in DNA

Question 4

Differences in Bone Measurements

Answer 4

Measurement: Females Males
Scapula - length of glenoid cavity <26mm >28mm

Humerus - diameter of head <43mm >47mm

Radius - Diameter of head <21mm >24mm

Radius - transverse diameter of <33mm >36mm
distal articular surface

Femur - diameter of head <43mm >48mm

Femur - bicondylar breadth <72mm >78mm

Question 5

Stature

Answer 5

• Taller = likely to be male
• Smaller = likely to be female
• Bone appearance is a key indicator of sex

Question 6

Morphological adaptations in the skull

Answer 6

• Supraorbital Ridge: (Bit across forehead)
  
  • Women = Smooth
  • Men = Pronounced
• Supraorbital Margin: (Within the eye socket)
  
  • Women = Sharp
  • Men = Rounded
• Mental Eminence: (Chin shape)
  
  • Women = Rounded
  • Men = Sharp
• Mastoid Process: (Bottom Back of skull)
  
  • Women = Small
  • Men = Large
• Nuchal Crest: (Middle back of skull)
  
  • Women = Smooth
  • Men = Hooked, Strong, Predominant

Question 7

Morphology of the pelvis

Answer 7

FEMALE:
- Lower/Broader
- Flatter iliac blades
- Wider Pelvic inlet
- Less angulated iliac crest
- Hip joint or acetabulum faces more anteriorly
- Widening at the sacro-iliac joint results in wider sciatic
notch
- Auricular surface tends to elevated medially above the
surface of the illium

MALE:
- Converse of the above!

Question 8

The Female pubis

Answer 8

• Phenice characters
  
  • The ventral arc = arcs away from centre
  • Sub-Pubic concavity = swoops up and away
  • Sub-pubic Ramus = Thick bone, thicker in females
• Larger Sub-pubic angle than males
• Longer pubic rami

Question 9

Accuracy of Skeletal sex determination

Answer 9

• Identification of sex - influenced by age, population
  affinities, preservation and completeness of the
  skeleton
• Typical accuracies for adult skeletons:
  
  • 95% = whole skeleton
  • 90% = pelvis
  • 80% = Cranium
  • 70% = Long bones
• Accuracy can be tested by :
  DIRECT TEST = classification of individuals of known sex
  INDIRECT TEST = Calculation of numbers of males and
  females in a skeletal sample of known (inferred) sex ratio

Question 10

Sexing Juvenile Skeletons

Answer 10

• Reliable sex difference appear at puberty

- Some with developed permanent teeth can be sexed