Transcript anthropology powerpoint

Forensic Anthropology:
Studying Bones
http://people.stu.ca/~mclaugh/skeleton8a.GIF
What are 3 questions that would
be very important to answer
when a set of “bones” (or
material that might be bones) is
discovered?
First Three Questions:
1. Are the remains actually bone?
macroscopic and microscopic study
2. Are the remains Human?
appearance and DNA if available
3. Are the Remains Ancient or Modern?
look for clothing, historic remains, teeth
If human, then proceed to identify the remains
So Why Study Bones?...
Why Study Bones?
• They constitute the evidence for the study of fossils.
• 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
A Caveat
• Informative features about the age, sex, race
and stature of individuals based on bones is
based on biological differences between sexes
and races (males are generally taller and more
robust) as well as differences due to ancestry
(certain skeletal features of the skull)
• However, it is imprecise because so much
human variation exists and because racial
differences tend to homogenize as populations
interbreed
• Still differences do exist and the more features
you survey, the more precise your conclusions
will be
-What can we learn from bones
(characteristics)?
-What are the specific bones that can tell us
this?
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)
http://en.wikipedia.org/wiki/Forensic_anthropology
- What does bone do? What are the
functions of bones in the body?
- What about Cartilage, Tendons, and
Ligaments?
Tissues and Functions of the Human
Skeletal System
• Bone
– Movement
– Support
– Calcium Storage
– Red Blood Cell Production
– Protection of Internal Organs
Tissues and Functions of the Human
Skeletal System
• Cartilage
– In a fetus, skeleton is made of cartilage, later
replaced by bone
– Covers ends of bones (especially at joints)
• Tendons
– Connect muscles to bone
• Ligaments
– Connect one bone to another bone
What is bone?
• Organic material (collagen= spongy protein) inside
of an inorganic matrix (mostly calcium and
potassium)
– Osteocytes: bone cells
How does bone form and grow?
• By early twenties, most human bone
growth is complete.
• Osteoclasts circulate and recycle
damaged bone cells…”remodeling”
– Most obvious where bone ends (epiphysis)
meet the bone shaft (diaphysis)
– “growth plate” or “epiphyseal” plate (Can tell
age of person)
• Growth in periosteum (membrane acting
as a bone cover—not at joints)
How many bones are in the human body?
How many?
• About 206- depending on age of person
• 176 in a newborn baby
- A lot of bones have not turned from
cartilage to bone yet
What kind?
• Long bones (femur, humerus,
radius, ulna, tibia and fibula)
• Short bones (metacarples and
metatarsals—hand bones and
foot bones)
• Flat bones (cranial bones, hip
bones, shoulder blades)
• Irregular bones (vertebra,
carpals, tarsals, many cranial
bones)
Parts of the skeleton
• Axial skeleton:
– skull (cranium), vertebral column, ribs
• Appendicular skeleton:
– Pectoral girdle (scapula and clavicleforms shoulder)
– Pelvic girdle (innominate or hip bones)
– Upper limbs (humerus, radius, ulna, etc)
– Lower limbs (femur, tibia, fibula, etc)
1. Determination of Sex
• Pelvis is the best bones (differences due to
adaptations to childbirth)
1. females have wider subpubic angle
2. females have a sciatic notch > 90°
3. females have a broad pelvic inlet
2.
3.
3.
1.
1.
2.
1. Determination of Sex
• Pelvis best (another view)
1. females have wider subpubic angle
2. females have a broad, shovel-like ilium
3. females have a flexible pubic symphysis
2.
3.
1.
2.
1.
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)
Sex Determination - Skull
Trait
Female
Upper Edge of Eye Orbit
Male
Sharp
Blunt
Round
Square
Zygomatic Process
Not expressed beyond
external auditory
meatus
Expressed beyond external
auditory meatus
Nuchal Crest (Occipital
Bone)
Smooth
Rough and bumpy
External Occipital
Protuberance
Generally Absent
Generally present
Frontal Bone
Round, globular
Low, slanting
Mandible shape
Rounded, V-shaped
Square, U-shaped
Ramus of mandible
Slanting
Straight
Shape of Eye Orbit
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 305.9 mm, while it is
339.0 mm in males
Determination of Race
• It can be extremely difficult to determine the true race of
a skeleton for several reasons:
– Forensic anthropologists generally use a three-race model to
categorize skeletal traits: Caucasian (European), Asian
(Asian/Amerindian), and African (African and West Indian).
– Not all individuals have skeletal traits that are completely
consistent with their geographic origin.
– 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.
– the vast majority of the skeletal indicators used to determine
race are non-metric (not involving measurements) 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.
European, Asian, African
From: Beyers, S.N. (2005). Introduction to Forensic Anthropology
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
Maxillae
Note shapes of nasal openings…
African
Asian
Shovel-shaped incisors
European
Spatulate (flat backed) incisors
General Shapes of the Eye Orbits
From: Beyers, S.N. (2005). Introduction to Forensic Anthropology
Determination of Race:
European
Trait
Orbital openings:
round
Nasal Index:
<.48
Nasal Spine:
Prominent spine
Nasal Silling /
Guttering:
Sharp ridge
(silling)
Prognathism:
Straight
Shape of
Orbital
Openings:
Rounded,
somewhat
square
Nasal spine:
Prominent
Progathism: straight
http://upload.wikimedia.org/wikipedia/en/c/cc/Skullcauc.gif
Determination of Race:
Asian (Asian decent
and Native American
decent)
Trait
Nasal Index
Nasal Spine
.48-.53
Somewhat
prominent
spine
Nasal Silling/
Guttering
Rounded ridge
Prognathism
Variable
Shape of
Orbital
Openings
Rounded,
somewhat
circular
http://upload.wikimedia.org/wikipedia/en/b/b3/Skullmong.gif
Determination of Race:
African: (people 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
http://upload.wikimedia.org/wikipedia/en/5/5e/Skullneg.gif
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
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)
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.
Cartilage is darker on xray
than solid bone. Epiphyses
aren’t fused yet.
No cartilage visible. Epiphyses
are fused.
Epiphyseal Fusion:
A General Guide
2a. Age Determination: Use of
Teeth
http://images.main.uab.edu/healthsys/ei_0017.gif
http://www.forensicdentistryonline.org/Forensic_pages_1/images/Lakars_5yo.jpg
2b. Determination of Age from Bone: Signs
of wearing and antemortem injury
Occupational stress wears
bones at joints
Surgeries or healed wounds
aid in identification
http://library.med.utah.edu/kw/osteo/forensics/pos_id/boneid_th.html
3. Estimation of Stature
• Intact Corpse – easy
• Dismembered – must be based on long
bones of the corpses
• Trotter Method – mathematical regression
formula based on the Terry collection and
hundreds of servicemen from WW II and
the Korean War.
• Ideally all long bones are available for stature
determination.
• Bones are measured using an osteometric board for
accuracy.
• The measurements are then put into standard formulae
3. Determination of Stature
(cont’d.)
• 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) + 78.10 cm
= 2.89 (30.8) + 78.10 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)
http://library.med.utah.edu/kw/osteo/forensics/index.html
Clues to Cause of Death
• Beveling
– Exit side is larger in
diameter than entrance for a
high velocity projectile
(bullet)
• Cut Marks, Chop Marks,
Scrape Marks
– Caused by a tool
• Gnaw Marks
– Postmortem- caused by animal
activity
Clues to Cause of Death
• Hyoid Bone
– Attachment for tongue, mandible, larynx,
etc…
– U-shaped bone in neck
– Fracture suggests strangulation
Identification of an Individual
• Dental records
• Antemortem x-rays (show old fractures,
implants, etc)
• Frontal Sinuses
• DNA (if possible- in teeth and marrow)
Time Since Death
• Bones are subject to weathering and
scatter.
• Bodies left on the surface are
skeletonized within 8 months.
• If buried, it will take between 1 and 2
years to become completely
skeletonized and in arid areas bodies
may become mummified.
Time of Death
• Scatter is important to the Forensic Anthropologist in
estimating time of death and burial.
• The number and types of bones available at the scene
indicates the amount of time the body has been in that spot
(smaller bones get lost first).
– 3 weeks: articulated bones
– 5 weeks: some scatter, some articulated
– 4 months: disarticulated, within 10’ circle
– 7 to 8 months: most bones within 10’ circle and all within
20’
– 1 year: small bones missing, complete disarticulation
– 2 to 4 years: some bones broken, scattered 40’, some
large bones missing
– 12+ years: bone rot
“The Body Farm”
• Facility instituted at the University of
Tennessee by Dr. William Bass
• Human decomposition is scientifically
studied to help us understand decay
process as well as how to determine a
better estimate of time since death and
cause of death
Sources:
• A very good website with photos and information
on forensic anthropology (including estimating
age, stature, sex and race):
– http://library.med.utah.edu/kw/osteo/forensics/index.ht
ml
• A good site with a range of resources:
– http://www.forensicanthro.com/
• Another good primer for determining informtion
from bones:
– http://www.nifs.com.au/FactFiles/bones/how.asp?page
=how&title=Forensic%20Anthropology
• Great, interactive site:
– http://whyfiles.org/192forensic_anthro/