Forensic Anthropology: Studying Bones. Forensic Anthropology

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1 Forensic Anthropology: Studying Bones Forensic Anthropology Forensic anthropology is the application of the science of physical anthropology and human osteology in a legal setting, most often in criminal cases where the victim's remains are in the advanced stages of decomposition. 1

2 Forensic Anthropology A forensic anthropologist can assist in the identification of deceased individuals whose remains are decomposed, burned, mutilated, or otherwise unrecognizable. Skills of a Forensic Scientist The analysis of skeletal, badly decomposed, or otherwise unidentified human remains is important in both legal and humanitarian contexts. In addition to assisting in locating and recovering human skeletal remains, forensic anthropologists work to assess the following features from a skeleton. the age, sex, ancestry, stature, and other unique characteristics. 2

3 The Bones Know Bones offer amazing clues to the trained eye. A trained forensic anthropologist, using techniques favored by archeologists, can identify illness, pregnancies, and possible careers of the deceased. It is also possible to determine other activities the deceased individual was involved with in life. The Bones Know Craniosacral measurements (skull measurements) have been established for all ages and race groups, which allow forensic anthropologists to establish a better picture of the deceased. The skull features unique racial identifiers such as the length of jaw and the distance between eye sockets. 3

4 The Bones Know The bones also hold clues to what work the person did. Bony ridges form where the muscles attach and have pulled over the years. A bony ridge on the wrist may indicate that the decedent used their hands for a living, such as a chef or seamstress. Forensic Anthropology It s the application of physical anthropology to the legal process. Identify skeletal, badly decomposed or unidentified human remains for legal and human reasons. Started during the 19 th century, popular during 1930s because of WWII and the Korean War. 4

5 Forensic Anthropologists can often answer many questions: Are the remains human? Are the remains a single individual or mixed remains of several individuals? When did the death occur? What are the gender, age, and race of the individual? Forensic Anthropologists can often answer many questions: What caused the death? What kind of death was it a homicide, a suicide, and accident or a natural death, or is the cause still undetermined? Did the individual have any anatomical peculiarities, signs of disease, or old injuries? 5

6 Forensic Anthropologists can often answer many questions: Can the individual s height, body weight, and physique be estimated? Forensic Anthropology Role of the Forensic Anthropologist: Recover Human Remains Identify Human Remains Determine Time or Cause of Death 6

7 Forensic Anthropology > Recovering Remains Locating Human Remains Cadaver dogs Remote sensing methods Forensic Anthropology > Recovering Remains Anthropologists can help: Find small bones or bone fragments Recover clothing and trace materials associated with bones Prevent damage of bones Map the location of bones and maintain chain of custody 7

8 Why Study Bones? They constitute the evidence for the study of fossil man. They are the basis of racial classification in prehistory. They are the means of biological comparison of prehistoric peoples with the present living descendents. They bear witness to burial patterns and thus give evidence for the culture and world view of the people studied. They form the major source of information on ancient diseases and often give clues as to the causes of death. Their identification often helps solve forensic cases. From: "Human Osteology - A Laboratory and Field Manual" 3rd Edition, 1987 What Can We Learn? Determination of Sex Pelvis Skull Determination of Race Skull Approximate Age Growth of long bones Approximate Stature Length of long bones Postmortem or antimortem injuries Postmortem interval (time of death) 8

9 Determination of Gender Male vs. Female Pelvis The best indicators of gender : Some bones display specific features which can be used to help determination of the sex of the skeleton. The best indicators are the: Skull Pelvis Head of the Femur 9

10 Sex Estimation Adult Usually related to size in adult long bones Male bones: usually larger, longer in a single population be cautious if different populations are involved Maximum diameter of head of humerus and head of femur may be used. Much more difficult to estimate sex in children s skeletons. Sex Estimation: Skull Good area for sex determination Generalization: male skull more robust, muscle marked than female: Sex estimation: face, mandible, vault 10

11 Sex Estimation: Face 1. Supraorbital (Brow) ridges: more prominent in males 2. Superior orbital margin: sharper in females 3. Palate: larger in males 4. Teeth: larger in males (Bass) 5. Mastoid process: more prominent and rugged in males. 6. Orbit (Eye socket): Rounder in females, more rectangular in males 7. Chin: more pronounced in males and larger jaws. 8. Sloping forehead in males higher, rounded in females 11

12 Skull differences 12

13 Angle of the Jaw 1. Determination of Sex Pelvis is the best bons (differences due to adaptations to childbirth) 1. Females have wider subpubic angle > 90 o in women < 90 o in men

14 Why does a female s subpubic angle need to be greater than 90 o? 1. Determination of Sex Pelvis is the best bones (differences due to adaptations to childbirth) 2. Females have a sciatic notch >

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16 1. Determination of Sex Pelvis is the best bones (differences due to adaptations to childbirth) 3. Females have a broad pelvic inlet Males have a more narrow pelvic inlet

17 Determination of Sex The acetabulum - the socket in the pelvis, which is used to secure the head of the femur - is larger in males than in females. Gender with Skulls Male vs. Female Skull 17

18 Forensic Anthropology Determining Sex using the skull Male (left) and female (right) skulls 1. Determination of Sex: Cranium Crests and ridges more pronounced in males (A, B, C) Chin significantly more square in males (E) Mastoid process wide and robust in males Forehead slopes more in males (F) 18

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20 Sex Determination - Skull Trait Female Male Upper Edge of Eye Orbit Sharp Blunt Shape of Eye Orbit Round Square Zygomatic Process Nuchal Crest (Occipital Bone) External Occipital Protuberance Not expressed beyond external auditory meatus Smooth Generally Absent Expressed beyond external auditory meatus Rough and bumpy Generally present Frontal Bone Round, globular Low, slanting Mandible shape Rounded, V-shaped Square, U-shaped Ramus of mandible Slanting Straight 1. Determination of Sex Normally, the long bones alone are not used alone to estimate gender. However, if these bones are the only ones present, there are characteristics that can be used for sex determination. E.g. maximum length of humerus in females is mm, while it is mm in males 20

21 Determination of Race It can be extremely difficult to determine the true race of a skeleton for several reasons: First, forensic anthropologists generally use a three-race model to categorize skeletal traits: Caucasian (European), Asian (Asian/Amerindian), and African (African and West Indian). Although there are certainly some common physical characteristics among these groups, not all individuals have skeletal traits that are completely consistent with their geographic origin. Second, people of mixed racial ancestry are common. Often times, a skeleton exhibits characteristics of more than one racial group and does not fit neatly into the three-race model. Also, the vast majority of the skeletal indicators used to determine race are non-metric traits which can be highly subjective. Despite these drawbacks, race determination is viewed as a critical part of the overall identification of an individual's remains. White, Asian, African From: Beyers, S.N. (2005). Introduction to Forensic Anthropology 21

22 Features of the Skull Used in Race Determination Nasal index: The ratio of the width to the height of the nose, multiplied by 100 Nasal Spine Feel the base of the nasal cavity, on either side of the nasal spine do you feel sharp ridges (nasal silling), rounded ridges, or no ridges at all (nasal guttering)? Prognathism: extended lower jaw Shape of eye orbits (round or squareish Nasal spine Nasal Silling and Guttering From: Beyers, S.N. (2005). Introduction to Forensic Anthropology 22

23 General Shapes of the Eye Orbits From: Beyers, S.N. (2005). Introduction to Forensic Anthropology 23

24 Determination of Race: Caucasian Trait Nasal Index: <.48 Orbital openings: round Nasal Spine: Prominent spine Nasal Silling / Guttering: Sharp ridge (silling) Nasal spine: Prominent Prognathism: Straight Shape of Orbital Openings: Rounded, somewhat square Progathism: straight Determination of Race: Asian (Asian decent and Native American decent) Trait Nasal Index Nasal Spine Nasal Silling/ Guttering Prognathism Shape of Orbital Openings Somewhat prominent spine Rounded ridge Variable Rounded, somewhat circular 24

25 Determination of Race: African: (everyone of African decent and West Indian decent) Trait Nasal Index >.53 Nasal Spine Very small spine Nasal Silling/ Guttering No ridge (guttering) Prognathism Prognathic Shape of Orbital Openings Rectangular or square Determination of Age The long bones are those that grow primarily by elongation at an epiphysis at one end of the growing bone. The long bones include the femurs, tibias, and fibulas of the legs, the humeri, radii, and ulnas of the arms, and the phalanges of the fingers and toes. As a child grows the epiphyses become calcified (turn to hard bone) 25

26 Cartilage is darker on xray than solid bone. Epiphyses aren t fused yet. No cartilage visible. Epiphyses are fused. 2. Determination of Age from Bones Ages 0-5: teeth are best forensic odontology Baby teeth are lost and adult teeth erupt in predictable patterns Ages 6-25: epiphyseal fusion fusion of bone ends to bone shaft epiphyseal fusion varies with sex and is typically complete by age 25 Ages 25-40: very hard Ages 40+: basically wear and tear on bones periodontal disease, arthritis, breakdown of pelvis, etc. Can also use ossification of bones such as those found in the cranium 26

27 Epiphyseal Fusion: A General Guide Epiphyseal Fusion The figures below are of the Epiphyses of the femur or thigh bone (the ball end of the joint, joined by a layer of cartilage). The lines in the illustrated Image 1 show the lines or layers of cartilage between the bone and the epiphyses. The lines are very clear on the bone when a person, either male or female is not out of puberty. In Image 2, you see no visible lines. This person is out of puberty. The epiphyses have fully joined when a person reaches adulthood, closing off the ability to grow taller or in the case of the arms, to grow longer. Figure 1. Figure 2. 27

28 2. Determination of Age from Bone: Signs of wearing and antemortem injury Occupational stress wears bones at joints Surgeries or healed wounds aid in identification 2. Age Determination: Use of Teeth

29 3. Determination of Stature Long bone length (femur, tibia, humerus) is proportional to height There are tables that forensic anthropologists use (but these also depend to some extent on race) Since this is inexact, there are confidence intervals assigned to each calculation. For example, imagine from a skull and pelvis you determined the individual was an adult Caucasian, the height would be determine by: Humerus length = 30.8 cm Height = 2.89 (MLH) cm = 2.89 (30.8) cm = 167 cm (5 6 ) ± 4.57 cm See your lab handout for more tables 4. Other Information We Can Get From Bones: Evidence of trauma (here GSW to the head) Evidence of post mortem trauma (here the head of the femur was chewed off by a carnivore) 29

30 Sources: A very good website with photos and information on forensic anthropology (including estimating age, stature, sex and race): ml A good site with a range of resources: Another good primer for determining informtion from bones: =how&title=forensic%20anthropology Great, interactive site: 30