Identifying human versus non-human skeletal remains in the field

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Identifying human versus non-human skeletal
remains in the field

• Amy E. Kelly
• Forensic Investigator
• Coconino County Medical Examiners Office

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Human vs. Non-human

• In modern forensic cases, 25-30 of the presented
  cases are non-human in origin.
• Access to and using a comprehensive comparative
  collection is necessary.
• Using a variety of literature in the field is
  helpful and an easy and efficient means to
  improve animal vs. human identification
  (Cruz-Uribe and Klein 1994, Gilbert 1990,
  Ubelaker 1989).
• If in any doubt, GPS, photograph and describe the
  specimen and scene before moving or collecting
  the remains and bringing it to the CCME office
  for analysis. If appropriate, call me or the CCME
  investigator on-call.

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Human vs. Non-human

• The first question that should be asked is Is it
  bone? and not wood, shell or plastic or rock.
• If yes, is it cranial or post-cranial? (cranial
  bones are usually thin, flat or even irregular in
  structure look for sinuses, sutures or sockets)
• Post-cranial bones are typically long, skinny and
  can be flat. Exceptions are the bones of the
  hands and feet, vertebrae and the pelves.
• Then, look to see if the bone is whole or
  fragmented.
• Also, are the bones adult in age or juvenile?
  (Fused or unfused epiphyses)
• And lastly but most importantly, could this be
  human?

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Human vs. Non-human

• Most mammalian bones share similar morphological
  features between species. The exceptions are
  marine mammals and some unusual critters like
  tree sloths.
• The primary difference is size. However some
  animals, such as deer, have bones that are very
  close in size to an adult human.
• Other mammals that cause confusion are bear and
  raccoon for their paws (Klepinger 2006). Bear
  paws look similar to adult hands and raccoon paws
  are easily confused for childrens hands.

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Human vs. Non-human

• Which hand is human versus bear?

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Human vs. Non-human

• Human versus raccoon

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Human vs. Non-human

• Easy identifications

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Human vs. Non-human

• But what if you come across bones like these?

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Human vs. Non-human

• Humans bipedal
• Pelvis is broad and shallow (bowl-shaped)
• The femur is the longest bone in the body with a
  single linea aspera
• The tibia and fibula are separate bones and the
  tibia is triangular in cross-section with a small
  tibial tuberosity
• Long and narrow foot with multiple bones for
  bipediality
• Other mammals Quadrupedal (mostly)
• Pelvis is long and narrow
• The femur is short relative to the body size. If
  the femurs length is comparable to an adult
  human femur, the diameter may be twice as thick
  as a human femur (i.e., cow) with a double or
  plateau linea aspera
• The tibia and fibula are often fused and the
  tibia is more rounded in cross-section with a
  large tibial tuberosity or longitudinal ridge.
• Legs of larger mammals are modified toes and
  fingers for speed and agility

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Human vs. Non-human
Vertebrae

• Humans
• Large, broad and flat vertebral body
• Short spinous process (2-3 inches at the most)
• Sacrum is triangular in shape and composed of 5
  fused vertebrae, which are broad compared to
  length and flattened anteriorly-posteriorly
• Other mammals
• Small vertebral body, often convex on one side
  and concave on the other
• Long spinous process (gt6 inches in some larger
  mammals)
• Sacrum is long and narrow with fewer fused
  vertebrae (3-4)

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Human vs. Non-human
Forelimbs

• Humans
• Designed for rotation (i.e., throwing, swinging)
• Long axis of scapula is perpendicular to scapular
  spine, which is why its triangular shaped
• Clavicle present
• Humerus, radius and ulna are not weight bearing
  so they are not robust. Ulna and radius not fused
• Large thumb
• Other mammals
• Designed for front-back stride
• Long axis of scapula is parallel to scapular
  spine, which is why its rectangular shaped
• Clavicle absent in most non-human mammals
• Humerus, radius and ulna are weight bearing and
  robust. Ulna and radius are often fused to
  support these weight bearing limbs
• Small thumb, even on mammals with similar hands
  (bear and raccoon)

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Human vs. Non-human

• Juvenile Remains
• The most common human bones to be mistaken for
  animal bones are bones from infants.
• The ends of the long bones, bones of the hands
  and feet and clavicle are not fused
• These unfused bones have indistinct edges
• Multiple ossification centers and unfused
  epiphyses increase the number of bones in infants
  and children
• Epiphyses (the ends of long bones) when separated
  from the rest of the skeleton do not look human
  to the untrained eye
• Long bones are thinner in cross-section
• Cranial bones can separate and lack the diploe
  structure, are uniform in thickness and can be
  confused with tortoise carapace. Petrous portion
  is separate in infants and due to its dense
  nature, often survives burial better
• Can be confused with smaller mammals such as
  raccoon, rabbit or even bird

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Human vs. Non-human
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Human vs. Non-human

• Mandibles from infants

Petrous bones circled
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Human vs. Non-human

• Human infant and fetal bones, recovered from a
  burial

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Human vs. Non-human

• Fragmented and burned remains are more
  challenging to correctly identify than intact
  remains for distinguishing between human and
  non-human remains
• Ids can be done macroscopically by morphology
• Ids can be done microscopically (histological
  examination)
• For our purpose, we only need to discuss
  macroscopic analysis

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Human vs. Non-human

• Skull Fragments?

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Human vs. Non-human

• Fragmentary and burnt bison bones.

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Human vs. Non-human
Traumatized and burned pig bones
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Human vs. Non-human

• Macroscopic characteristics cortical bone much
  thicker in animal long bones than in human
  humeral and femoral cortical thickness in humans
  is about ¼ of total diameter
• Bone macroscopic characteristics cranial bone
  diploe relative to cranial cortical (tabular)
  bone is thinner in animals compared to humans

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Human vs. Non-human

• Review
• Ask first, Is it bone?
• Ask second, Could it be human and why? (i.e.,
  context, size/shape of bones, do the bones fit
  bipedal locomotion?)
• Have some reference material to aide in more
  accurate assessment of human versus animal (I can
  provide photocopies)
• If in doubt, no matter how much, GPS, photograph
  and document the remains, then collect or call me
  or the on-call investigator

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Human vs. Non-human
Call me directly if you ever come upon this
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Human vs. Non-human

• Thanks to the following
• Staff at CCME for support while I write lectures
  and play with bones.
• CCSO CI and SAR for all your hard work and
  selfless dedication to helping victims and their
  families with the multitude of hours and energy
  invested to ensure recovery.
• My dear friends and boyfriend who watch my child
  so I can present these lectures.

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For Joe