WEEK 2- sex estimation in adults Flashcards
What is biological sex?
Based on reproductive system
phenotypical expression of chromosome X or Y
caused by natural and sexual selection over evolutionary time
What Is gender?
Social construct/ concept
social structuring based on various factors including biological sex differences
reflects different political, economic, social and reproductive strategies
what are the key difference between male and females?
- Skeletal consequences of sexual dimorphism
- Size- adult males are often larger than females- males have more muscle attachments, can look at molar teeth
- Robusticity- males greater muscle bulk, stronger muscle attachments and larger joint surfaces
- Reproduction- the female pelvis is adapted for childbirth and my show evidence of parturition trauma
- Bone chemistry- sex differences in bone mineral content, trace element levels, dietary stable isotopes and DNA
- Behaviour- culturally induced sex differences in patterns of trauma, body modification and stress markers (tattoo- soft tissue, but cutting teeth into pattern may assist in identifying)
What is estimation of sex of a skeleton influenced by?
Age, population affinities and preservation
Accuracy of sexing the skeleton by different bones?
- 90-95% for whole skeletons
- 90% pelvis
- 80% cranium
- 70% long bones
Accuracy and bias estimation
Direct tests= effectiveness in classifying known sex individuals
Indirect tests= calculation of the sex ratio in a representative sample of skeletons
Main diagnostic traits are
Skull and pelvis
What are most of the traits form?
Most traits relate to either muscle attachment of child birth- muscles of mastication leave marks on males
How many diagnostic traits are there for the skull?
25
Main diagnostic traits
- nuchal crest- Female= smooth, male= ridged
- mastoid process- female= small and inflected, male- large and vertical
- orbital margin- female= circular and sharp, male= quadrangular and rounded
- Supra-orbital ridge/glabella, Female= slight, male= prominent
- mental eminence, female= small and rounded, male= large and projecting
What are the osteological catergories?
Definite female- F possible female- f? indeterminate- ? possible male - m? definite male- M
What do sex diagnostic traits of skull depend on?
Ethnicity
European different from Asian
example- mastoid process in Asians not as pronounced
Overall difference in male and female pelvis
Female- shallower, broader and more rectangular in anterior view, with wider subpubic space
Which parts of the pelvis can be measured?
1, smaller acetabulum
- medial extension of pubis
- triangular obturator foramen
How many sex diagnostic traits are there for the pelvis?
25 main ones: pubic inlet- broad and oval in F greater sciatic notch- U shaped, obtuse >60 F sub pubic angle- Broad and U shaped F
Where are sex difference of the pelvis found?
Anterior aspect of the pubic symphysis and the medial aspect of the inferior pubic ramus
When do the characteristics of the pelvis develop?
Late adolescence
reliable indicators of sex in several populations
How can the femur determine sex?
Middle of the shaft
width measured
Discriminant function analysis of hip bone
DF= (25.15x A /P )/ (0.132 x I) - 31.84 A= acetabulum diameter I= ischial length- upper acetabulum to lower margin of ischial tuberosity P= pubic length- upper margin of pubic symphysis to nearest point on rim of ac
Results of DF
NEG= female Pos= male
Accuracy of the DF measurements?
98% Accuracy
Measurements of the femur
Length, prox and head diameter
femur mids diameter
talus length
clavicle diameter
Discriminant analysis
linear combinations of multiple measurements provide evidence for discrimination between defined groups
different measurements are weighted by coefficients then all weighted measurements are summed and given discriminant score
Potential skeletal indicators of pregnancy
- Discrete zones of cortical resorption (pits) on the hip bone, particular along the posterior region of the pubic symphysis
- extended pubic tubercle (attachment of inguinal ligament and rectus abdominal muscle)
- scarring where ligaments torn or made in pitting into bone
What can the pelvis say about birth?
If its been had
NOT how many times
Prominent pubic tubercle
Pitting along the posterior (dorsal) margin of the pubic symphysis
Sexing immature skeletons
Before puberty
no real way to tell
reliable skeletal sex difference emerge at puberty
What influences sex diagnostic trait development
hormones
Sexing kids using teeth
Permanent tooth crowns- M1 and M2 children with those teeth statistically (6-8 years)
Sex diagnostic traits in children
- mandibular symphysis
- gonial angle on mandible
- greater sciatic notch
- iliac crest curvature
- orbital margins
Sex specific genetic material
Used to estimate well preserved sub adult skeletons
Biomolecular methods of sex estimation
Amplification of amelogenin genes
- small lengths of DNA are amplified with short 6bp differences detected between X and Y
- these sequences are only present as single copies per chromosome
- allelic dropout can also affect the accuracy of procedure, resulting in an XY individual being recorded as X
Amplification of Y- repeat sequences
- Y repeat are short sequence present in multiple copies within the y chromosome
- presence of Y repeat DNA indicates a male, but absence of the sequence could result from failure of the method
Method
Costly
Worth doing for small numbers
Pick out Y chromosome to say if its male but cant see if its female as it might but also might be an error
Measurements of the humerus for sex
measure the head width and the bi-epicondular width
Measuring the radius
Transverse width
head width
Femur width
Head and bicondylar width
