Ch.10: Age Estimation

Estimation requires…

…extensive knowledge on the “nature, sequence, and timing of skeletal changes across the life span” (p.247)

• Estimations should use populaton-specific methods

Skeletal age estimation…

…correlates biological age with chronological age

• Use this estimation to include or exclude individuals on a list of missing persons or presumptive identifications

With older age, the discrepancy between biological and chronological age…

…increases

• The trajectory effect

Skeletal Age

• Subadult (juvenile)

• Adult

• Completion of growth and development

Subadult (juvenile)

• “Embryonic, fetal, infant, child, and adolescent periods (p. 248)

• Growth and development of bones and teeth

• Emphasis on dental development and eruption

Adult

• Ages “occurring during the mature, degenerative stages of skeletal change” (p. 248)

• A “function of our evolutionary history and maintenance of bodily homeostasis” (p.248)

Completion of growth and development

• All permanent teeth have erupted

• All epiphyses have fused

Dental Anatomy

• “Teeth articulate with bone via the alveoli or tooth sockets” (p. 59)

  • Maxilla

  • Mandible

• Tooth Structure

  • Two major portions

  • Three types of calcified tissue

Maxilla

Upper teeth

Mandible

Lower teeth

Two major portions tooth structure

• Root

• Crown

Three types of calcified tissue

• Dentin

• Enamel

• Cementum

Subadult Age: Dental Methods

• Birth

• 1 year old

• 2-4 years old

• 6-12 years old

Birth

All deciduous teeth have begun to mineralize

1 year old

Permanent incisors and canines begin mineralizing

2-4 years old

• Premolars and second molars begin mineralizing

• By three years old, “all deciduous teeth have erupted with the completion of their roots” (p. 249)

6-12 years old

Third molar crowns form

Dental development stages

• Assess the degree of development and position of each tooth

  • AlQahtani et al., 2010; Demirjian et al., 1973; Moorrees et al., 1963a, 1963b

  • Estimate age using calculated mean ages for the developmental stages of each tooth

• Third molar eruption

Females’ dentition tends to develop more…

…quickly than males’ dentition

Third molar eruption

Used to estimate the probability of the individual being older or younger than 18 years of age

Subadult Age: Osteological Methods

• Diaphyseal growth

• Primary ossification centers

• Epiphyseal Union

Diaphyseal growth

Strong “linear relationship between diaphyseal length and age, especially during fetal development” (p. 250)

Primary ossification centers

• Appearance and fusion

• Cranial sutures and fontanelles, long bones, hands, feet, “ribs, vertebrae, clavicle, and scapula” (p. 251)

Epiphyseal Union

• Predictable sequences of fusion

• Usually between the ages of 10-25 years old

• Reliable method

Adult Age: Pubic Symphysis

• The “best-documented area of the skeleton for adult age estimation” (p. 253)

• Features on and around the pubic symphysis

• Methods:

  • Brooks & Suchey 1990 and Hartnett 2010

Adult Age: Auricular Surface

• Degenerative changes of the auricular surface and the area of the ilium posterior to it

• Often more well-preserved than the pubic symphysis and sternal rib ends

• Methods tend to be difficult

Adult Age: Sternal Rib End

• Area of the rib where the bone connects to the costal cartilage 

• Changes in rib shape and bone quality 

Adult Age: Histological Methods

• Bone histomorphology

• Ellis Karley first developed this method in the 1960s

  • Methods have since been modified and improved

• Osteon population density (OPD)

• Considerations

Osteon population density (OPD)

• Number of complete osteons and osteon fragments per unit area

• After maximum OPD is reached, the individual can be no older than the method’s specified age

Considerations for Histological Methods

• Variation by element

  • Methods are bone-specific

• Differences in remodeling rates due to “age, sex, population affinity, physical activity, and nutritional/health status” (p. 256)

General Indicators of Advanced Age

• Regional changes in the skeleton

  • Reflect generally advanced age (not specific)

• Cranial suture closure

  • Complete obliteration is indicative of advanced age

• Osteoarthritis

• Osteoporosis

Osteoarthritis

• More common in advanced age

• Osteophytic lipping, porosity, eburnation

Osteoporosis

• Increase in bone porosity

• When bone resorption outpaces bone formation

  • More common in females

Other Considerations for Age Estimation

• An increased knowledge of microstructural and biochemical processes has improved age estimation methods

• Multifactorial age estimation

• Transition analysis

Multifactorial age estimation

The use of multiple “age indicators which are statistically combined to produce a single age estimate” (p. 258)

Transition analysis

• Bayesian approach

• Estimates “the mean age of the transition from one phae of state to the next”

Age slope

• Development

  • Young

• Middle

• Slope of Degradation

  • Old