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HUMAN VARIATION

DR KORI FILIPEK

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WHAT COULD BE IMPROVED

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REVIEW FROM PREVIOUS WEEKS

  • Foundation of Forensic Anthropology:

    • Based on human osteology and a fundamental understanding of human anatomy.

    • Biological growth and development inform key aspects of a biological/osteoprofile, including:

    • Age

    • Biological sex

    • Ancestry (to a limited extent)

    • Other key identifying features

    • Goal: Aid in human identification.

    • Primary Stakeholder: The victim.

    • Limitations in assessing characteristics:

    • Unable to assess eye/hair color or skin color from skeleton.

AIMS

  • Familiarization with Concepts:

    • Human skeletal variation

    • Distinguishing between metric and non-metric traits

  • Understanding Basis:

    • Looking at human variation in forensic anthropology

  • Appreciating Benefits and Limitations:

    • Human variation in forensic anthropology

ASSESSMENT OF HUMAN VARIATION

  • Methods:

    • Assessed through metric and non-metric analyses.

WHY ARE WE INTERESTED IN HUMAN VARIATION?

  • Individual Level Factors:

    • Age/Sex

    • Stature

    • Identity

  • Population Level Factors:

    • Biodistance

    • Mobility

    • Evolutionary processes

METRIC ANALYSES

  • Key Areas in Metric Analyses:

    • Anthropometry

    • Osteometry

    • Stature

    • Craniometry

BASIS OF METRIC ANALYSES

  • Anthropometry:

    • Systematic measurement of humans for:

    • Identification

    • Understanding proportions (size and shape)

    • Ergonomic design

    • Prostheses

    • Historical Interest:

    • The concept has been of interest since antiquity.

    • Protagoras (c. 490 BC):

    • Stated: "ἄνθρωπος μέτρον" (Man is the measure of all things).

VITRUVIUS AND DAVINCI

  • Vitruvius:

    • A Roman architect who wrote De architectura, describing perfect proportions of buildings using human attributes.

    • E.g.,

    • A palm is four fingers.

    • A foot is four palms.

    • A cubit is six palms.

    • Head length x 8 = height.

  • DaVinci's Contributions:

    • Created ‘Vitruvian Man’ as a basis of ‘perfect’ human proportions.

    • Formed an early basis for anthropometry.

DAVINCI’S VITRUVIAN PROPORTIONS

  • Key Proportions Analyzed:

    • Length of a man's outspread arms is equal to his height.

    • Maximum width of shoulders is a quarter of a man's height.

    • Distance from elbow to the tip of the hand is one quarter of a man's height.

    • Length of the hand is one-tenth of a man's height.

    • Distance from bottom of chin to nose is one-third of the length of the head.

    • Distance from hairline to eyebrows is one-third of the length of the face.

    • Length of the ear is one-third of the length of the face.

ANTHROPOMETRY IN FORENSIC SCIENCE

  • Historical Usage:

    • First used in 1883 by Alphonse Bertillon at Paris police.

    • Developed measurement systems for identifying criminals (repeat offenders).

  • Characteristics Measured:

    • Height, breadth, foot size, length and width of the head, middle finger length, left forearm length, and distinguishing features.

  • Bertillonage:

    • A photo system adopted as standard forensic practice in 1894.

CESARE LOMBROSO AND PHYSIOGNOMY

  • Contributions:

    • Founded 'anthropological criminology' in the late 19th century.

    • Believed moral character could be judged by outer appearance (biological determinism).

  • Criminality Indicators:

    • Measurements and craniofacial features related to criminality:

    • Large nose

    • Sloping forehead

    • Large jaws

    • Large brow ridges

    • Facial asymmetry

    • Large ears, lips, scars, tattoos

    • Left-handedness, thick eyebrows

    • Oblique eyes, facial prognathism, thin hair and beard, broad shoulders

NAZI ANTHROPOMETRY

  • Historical Misuse:

    • Misused human measurements to classify people by ‘race’.

    • Developed devices and measurement systems to assess size differences between Aryan vs non-Aryan skulls.

    • Illustrated the historical abuse of metrics.

OSTEOMETRY

  • Purpose in Forensic Anthropology:

    • Uses anthropometry to assess metric dimensions of bone, focusing on the relationship between skeletal and soft tissue appearance.

  • Definition:

    • Osteometry is the quantifiable description of morphological differences/characteristics in bone.

  • Standardized Measurements:

    • Measurements should always be taken from the left side of complete bones.

    • Must possess a research question/objective associated with measurements.

STATURE ESTIMATION

  • Importance:

    • A key aspect of the biological/osteoprofile.

    • Distinction between living stature vs anatomical stature.

  • Height Variation Factors:

    • Taller in the AM than PM (approximately 2-3 cm).

    • Average 6-8 mm decrease in intervertebral discs (IVD) every decade after age 30.

    • Self-reported heights often overestimate (men > women).

    • Height may be measured with shoes on.

CALCULATING STATURE

  • Estimating Stature:

    • Living height may be estimated from measuring skeletal elements.

    • Ideally requires estimation of sex, age, and ancestry (influenced by genetics and environmental factors).

    • Body proportions vary due to adaptation in climatic zones.

    • Stature increases during childhood and puberty - growth rates vary significantly, hence focus on adults.

  • Methodological Framework:

    • Use of mathematical formulae vs anatomical methods.

STATURE METHODS

  • Anatomical Method (Fully Method):

    • Involves measuring the height of each skeletal element contributing to living height.

    • Dependent on skeletal completeness.

    • Most accurate, considers varying body proportions (e.g., long trunk vs. short legs).

    • Corrections for missing soft tissue necessary.

  • Mathematical Method (Regression Formulae):

    • Measures long bones and uses sex-ancestry-specific regression equations to extrapolate living height.

    • Faster and applicable even from incomplete skeletons but produces a range due to population averages.

ANATOMICAL METHOD

  • Overview:

    • Adds up partial measurements of the axial skeleton.

    • Requires correction factors to attain final living stature estimations.

    • Revisions by Raxter et al. (2006) clarified metric dimensions.

MATHEMATICAL METHOD

  • Regression formulae for estimating stature from long bones in adults include:

    • Trotter (1970):

    • Stature = 70.45 + 3.08(Humerus) ± 4.05 cm

    • = 79.01 + 3.78(Radius) ± 4.32 cm

    • = 61.41 + 2.38(Femur) ± 3.27 cm

    • = 78.62 + 2.52(Tibia) ± 3.37 cm

    • = 63.29 + 1.30(Femur + Tibia) ± 2.99 cm

    • Jantz (1992):

    • Similar regression equations exist for estimating stature using long bones.

ESTIMATING BODY MASS

  • Relevance for Forensics:

    • Useful for forensic applications, though accurate methods are still under development.

  • Body Mass Index:

    • Categorized as:

    • Underweight (< 18.5)

    • Healthy weight (18.5-24.9)

    • Overweight (25.0-29.9)

    • Obese (> 30)

  • Method Summary:

    • Methods tested for estimating body mass show various prediction errors based on femoral head breadth (FHB), stature and living bi-iliac breadth (St/LBIB), with ranges provided for methods by different scholars (Ruff et al., Elliott et al.).

CRANIOMETRY

  • Historical Viewpoint:

    • From the 18th to 20th centuries, cranial shape and size were incorrectly correlated with cognitive ability and social traits.

  • Definition:

    • Involves measuring dimensions of the skull, such as maximum and minimum length or width and measurements between anatomical landmarks.

  • Purpose:

    • Identify patterns in skull shape that may not be appreciated visually.

CRANIOMETRIC CASE STUDIES

  • International Standards:

    • Measurements conducted under internationally standardized conditions (e.g., Martin (1928), Moore-Jansen et al. (1994)).

    • Noted that environmental factors affect genetic potential and there is variation due to congenital discrepancies.

CRANIAL INDICES

  • Cranial Index Calculation:

    • CI = width ÷ length × 100

    • Categories:

    • Dolichocephalic (long-headedness): CI < 76

    • Brachycephalic (broad-headedness): CI > 80

    • Note:

    • This simplification is questionable and its value is limited.

SUMMARY OF METRIC ANALYSES

  • Objective vs. Obstacle:

    • Osteometry is a standardized technique that produces more objective data.

    • When undertaking metric analyses, a clear question or objective is essential.

    • E.g., stature and proportions over time, sex assessment (forensics), migration patterns.

    • Variation in data is both a source of insight and a challenge.

NON-METRIC ANALYSES

BASIS OF NON-METRIC ANALYSES

  • Variation Types:

    • There is variation within (intra) and among (inter) populations.

    • Biodistance Measure:

    • A measure of relatedness or divergence among groups separated by time and/or geography, based on morphological variation.

    • Assumption:

    • Direct relationship between phenotype (non-metric variation) and genotype (genetic makeup).

TERMS & DEFINITIONS

  • Non-metric Traits:

    • Also known as: anatomical variants, discrete traits, discontinuously varying traits, epigenetic traits.

    • Essential to distinguish from pathology/manner of death.

CRANIAL NON-METRIC TRAITS

  • Common Examples:

    • Variation in cranial bones referred to as ‘Wormian bones’, ossicles, or extrasutural bones.

    • Can be associated with malnutrition, metabolic diseases, or inherited traits.

METOPISM

  • Definition and Significance:

    • Retention of the metopic suture; generally closes between 2-8 years.

    • Persistent metopism occurs in 1 to 15% of populations; can influence frontal sinuses.

    • Possible genetic or pathophysiological influences (e.g., iron deficiency anemia).

POST-CRANIAL NON-METRIC TRAITS

  • Examples:

    • Squatting facets often discussed as non-metric traits but have habitual causes.

DISCOVERIES OF NEW ANATOMICAL VARIATIONS

  • Recent Findings:

    • Presence of variations such as the fabella bone has increased in detection to the extent that it is now thought to be three times as common as 100 years ago.

MAIN CLINICAL PUBLICATIONS ON NON-METRIC TRAITS

  • Discussion Points:

    • Are these traits informative about population relatedness or better explained by lived experience?

DENTAL NON-METRIC TRAITS

  • Genetic Linkage:

    • Show potential linkage to genetic relatedness.

    • Scoring systems used for evaluation, with certain traits (e.g., shovel-shaped incisors) showing stronger links than others.

SUMMARY OF NON-METRIC TRAITS

  • Potential Uses:

    • Assessing potential relatedness within and between populations; revealing aspects of human identity and habitual behavior.

    • Importance of visibility for determining key traits.

LAB TODAY!

  • Upcoming Activities:

    • Engaging with various metric analyses, including practical measurement exercises and an osteology test.