Sexing of Skeletal Material

Sex Determination in Skeletal Remains

Outline• Determination of sex (cranial and postcranial

methods)

– Bioprofile: Ancestry, Sex, Age, Descriptive traits: Stature, Handedness, Cranial and post cranial indices, Non metric traits

Determination of Sex• Refers to biological sex as indicated by the X and the Y

chromosomes! • Does not refer to culturally defined gender identities!

• 50% chance of correct assessment!

• Sex should be determined before age as there are morphological changes that depend on sex!

• The techniques are based on the theories of growth and sexual dimorphism - the relative size and the distinctive physical differences between males and females.

• Overlapping features are not uncommon!

Determination of Sex

• Scoring system 1-5:

»1 = Female, »2 = Possible Female»3 = Ambiguous»4 = Possible Male,»5 = Male

• Subjective methods!• If too many ambiguous features or features lean towards both sides

equally = conclude ”sex undetermined”!

Parameters for Sex Determination• The sexual characteristics develop after puberty at different

rates for males and females

• In elderly individuals, the traits in both sexes may appear more masculine

• The Pelvic bones – The most accurate attributes for sex diagnosis– Becomes distinctive during the adolescent growth

• The Skull• Other skeletal and dental elements via metrical data

Accuracy• No method is 100% accurate, but some

of them come close.

• The Pelvis alone gives an accuracy of 95%• The skull alone 90%• The pelvis and skull together 98%• Long bones alone 80-90%• Long bones and pelvis 95%• Long bones and skull 90-95%

(Krogman & Iscan 1986)

Male

Female

Inlet

Outlet

Pelvic Cavity

Inlet

Outlet

Pelvic Cavity

The female pelvis is broad and squatter

The male pelvis is narrow and long

Subpubic Angle

Female = Large angle (>90 degrees) Male = Small angle (<90 degrees)

V-shaped, narrow and sharpU-shaped, wide and rounded

Subpubic Concavity

Female = Narrow and slightly concave Male = Broad and strait

Width of the Pubic Body

Female = Broad Male = Narrow

Ischiopubic Ramus(Medial aspect)

Female = Sharp edge Male = Broad edge

Ventral Arch

Female = Marked ventral arch Male = No marking

Obturator Foramen

Female = Triangular shape Male = Ovoid shape

Greater Sciatic Notch

Female Male

Female angle is larger and wider, more than 68º

Male angle is smaller, narrow and acute, less than 68º

The Auricular SurfaceFemale = Small and more L-shaped Male = Large and flat

Preauricular Sulcus

Female = well developed marked sulcus

Actually only present in about 25% of women

Male = small sulcus. Or more often just absent

Female Male

The preauricular sulcus is a groove frequently seen on the iliac bone, adjacent and parallel to the inferior surface of the sacroiliac joint.

Acetabulum

Female = Small-MediumFaces anterolaterally

Male = Medium-LargeFaces laterally

Sacrum

Female = Broad and short. Marked curvature at S1-2 and S3-5

Male = Narrow and large with an evenly distributed curvature.

Sacral alae are broad relative to body Sacral alae are narrow relative to body

See Bass (1995)

Sex Differences of the Cranium

• The skull is the second most useful structure for determining sex.

• Dimorphic characteristics vary between the ancestral groups!

Sex Differences of the Cranium

• The size and architecture• Frontal Bone• Supra-Orbital Ridge (Glabella)• Supra- Orbital Margin• Occipital Protuberance/Nuchal Crest • Mastoid Process • Zygomatic Arch • Mandible:

– Mental Eminence– Ascending ramus – Gonial angle

Frontal Bone

Forehead is high and rounded with juvenile gracile appearance

Forehead is low and slopes posteriorly. Loss of juvenile appearance

Supra-Orbital Ridge (Glabella)

Female Male

Female = smooth Male = Prominent

Supra-Orbital Margin

Female Male

Female = sharp margins

The overall orbital outline is rounded

Male = rounded margin

The overall orbital outline is squared

Occipital Protuberance/Nuchal Crest

Female Male

Female = No marked muscle attachments or protuberance(Not rugged)

Male = Marked muscle attachments and pronouncedprotuberance(Rugged)

Mastoid ProcessThe Sterno-cleidomastoid muscle, which holds the head up, attaches here!

Female Male

Female = Small – medium Male = Medium – Large. Drop-shaped

Zygomatic Arch

Female = Ends superior to acustic meatus.

Zygomatic process is thin.Zygomatic bone is smooth and low.

Male = Ends posterior to acustic meatus, superior to mastoid process.

Zygomatic process is thick.Zygomatic bone is smooth and low.

Mental Eminence/Protuberance

Female Male

Inferior view of mandible

Male = Large and projectingLower margin of mandible is thick

Female = small and roundedLower margin of mandible is thin

Ascending Ramus

Female = Narrow Male = Broad

Gonial Angle

Female = Angle is wide (> 120 degrees)

Male = Angle between 90-100 degrees

Slight or no angle flaring Prominent angle flaring

Discriminent Functions of the Cranium

Metrical Data Used for Sexing

Epicondyle breadth of Humerus(>61mm=M, <61mm = F)(From France 1983, cited in AFIP 2005: 40)

Range charts of male (light) and female (dark)Caucasoid Negroid

From Byers (2002:187)

Metrical Data Used for Sexing

12th Thoracic vertebraYu et al. (2008)

• Most pronounced sexual dimorphic traits evident in:

• 1. Coronal diameter of superior endplate of vertebral body

• 2. Ratio of anterior middle height of body

• 3. Length of mammilary process and pedicle

• Accuracy: up tp 90%Based on 102 Korean autopsi samples

Other Methods• Discriminate functions for sex determination using

(for example):

• The Internal Acoustic Meatus of the petrous portion– Diameter: 70% accuracy (Lynnerup et al. 2006)– Angle: 83% accuracy (Norén et al. 2005)

• DNA!

The Skeletal Report Layout• Titel Page• Abstract• Introduction• Inventory and Preservation• Analysis:

– Ancestry – Sex– Age– Descriptive traits:

• Stature• Handedness• Cranial and post cranial indeces

– Non metric traits– Pathology (incl. Trauma)

• Discussion & Conclusion• References• Appendices:

– Recording forms – Photoes– Radiographs

IntroductionCase background:

• What (e.g. single burial or part of a cemetry, mass grave)• Where (site name, parish, county)• When

– when was it excavated– When does it date (forensic or archaeological (e.g. AD 16th -17th Century)

• Who excavated it? (e.g. museum, police department, organisation etc)

Inventory and Preservation

• Fill in present bones on a skeleton drawing and substantiate by text.

• Pictures/drawings can speak a thousand words!

• Nobody wants to read a very descriptive inventory in words only!!!!

• MNI –any additional remains should be identified and data derived from these should be stated.

Preservation

Fragmented/Complete

Complete = >75% presentPartial = 50% - 75% presentPoor = 50-25% presentVery Poor = <25% present

Perimortem vs postmortem damage

• Perimortem : Occurs at or near the time of death

– Regular, linear, polished, sharp, smooth edges; Discolouration of bone. Staining from surrounding soil.

• Postmortem: Occurs after death

– Irregular, crumbly, rough white edges . No evidence of remodelling. Absence of associated fracture lines.

– E.g. Erosion, weathering, scavenging, excavation

– Describe surface structure of bone (e.g. porous, flaky)

– Density of bone –dense or fragile/light bone (age and pathology may lead to weakness of bone, but no conclusions at this stage)

– Describe the postmortem damage (where it is analtomically).

– Describe colour of bone (e.g. dark brown, light yellow)

– Brief conclusions regarding the taphonomic history of the skeleton (burial environment; Acidic/alkine soil, moisture/dryness, evidence of scavenging, weathering (bleaching etc). Usually with reference to archaeological record.

Preservation

Ancestry

Methodology:

Anthroposcopy: Cranio-facial variation and post-cranial variations

and

Osteometry: Metric observations (Cranid/Fordisc)

Results

Sex• Describe what you see

• Reference the methods you use!

• State the accuracy rate of the methods (only in forensic reports)

• Results

Age

• Describe

• Reference methods

• Discuss accuracy (forensic reports)

• Results

Descriptive Traits

• Stature (methods, bones used, results, accuracy)

• Craniometrics (e.g. Brachycrany = broad and round headed)

• Handedness

• Parity?

Non Metric Variation

Cranial

Post-cranial

Dental

And more….

• …pathologies

• Discussion of findings

• Conclusion

Literature cited

• Acharya AB and Mainali S. (2008) Sex Discrimination Potential of Buccolingual and Mesiodistal Tooth Dimensions. Journal of Forensic Science 53(4):790-792

• AFIP (Armed Forces Institute of Pathology) (2005) 18th Annual Forensic Anthropology Manual. National Museum of Health and Medicines,National Transportation Safety Board Training Academy, Ashburn, Virginia

• Black T (1978) A new method for assessing the sex of fragmentary skeletal remains femoral shaft circumference. American Journal of Physical Anthropology 25:333-339

• Byers, SN (2002) Introduction to forensic anthropology. A textbook. Allyn and Bacon, Boston.• De Vito C and Saunders SR (1990) A discriminant function analysis of deciduous teeth to determine sex. Journal

of Forensic Science 35:845-858• France D (1983) Sexual dimorphism in the human humerus. Unpublished Ph.D dissertation, University of

Colorado, Boulder.• Hunt EE and Gleser I (1955) The estimation of age and sex of pre-adolescent children from bones and teeth.

American Journal of Physical Anthropology 13:479-487• Jantz RL and Moore-Jansen PH (1988) A database for forensic anthropology: Structure, content and analysis.

University of Tennessee, Knoxville, Department of Anthropology. Report of Investigations No 47. Submitted to National Institute of Justice.

• Krogman WM and Işcan MY (1986) The human skeleton in forensic medicine. 2nd ed. Springfield IL: Charles C Thomas.

• Lynnerup N, Schulz M, Madelung A and Graw M (2006) Diameter of the human internal acoustic meatus and sex determination. International Journal of Osteoarchaeology 16:118-123.

• Norén A, Lynnerup N, Czarnetzki A and Graw M (2005) The Lateral Angle. A method for sexing using the petrous bone. American Journal of Physical Anthropology 128(3):318-323

• Schutkowski H (1993) Sex determination of infant and juvenile skeletons: I morphological features. American Journal of Physical Anthropology 90:199-206

• Stables D and Rankin J (2004). Physiology in childbearing with anatomy and related biosciences. England: Elsevier.

• Washburn SL (1948) Sex differences in the pubic bone. American Journal of Physical Anthropology 6(2):199-208

• Washburn SL (1949). Sex differences in the pubic bone of Bantu and Bushman. American Journal of Physical Anthropology 7(3):425-432

• Wilson LA, Macleod N and Humphrey LT (2008) Morphometric criteria for sexing juvenile human skeletons using the ilium. Journal of Forensic Sciences 53(2): 269-278

• Yu S-B, Lee U-Y, Kwak D-S, Ahn Y-W, Jin C-Z, Zhao J, Sui H-J and Han S-H (2008) Determination of Sex for the 12th Thoracic Vertebra by Morphometry of Three-dimentional Reconstructed Vertebral Models. Journal of Forensic Science 53(3):620-625