Identifying human versus non-human skeletal remains in the field Amy E. Kelly Forensic Investigator Coconino County Medical Examiner’s Office

Human vs. Non-human In modern forensic cases, 25-30% of the presented cases are non-human in origin. 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. 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). 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. 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.

Human vs. Non-human The first question that should be asked is “Is it bone?” and not wood, shell or plastic or rock. 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) 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. 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. Then, look to see if the bone is whole or fragmented. Also, are the bones adult in age or juvenile? (Fused or unfused epiphyses) Also, are the bones adult in age or juvenile? (Fused or unfused epiphyses) And lastly but most importantly, could this be human? And lastly but most importantly, could this be human?

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. 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. 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 children’s hands. 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 children’s hands.

Human vs. Non-human Which hand is human versus bear?

Human vs. Non-human Human versus raccoon Human versus raccoon

Human vs. Non-human Easy identifications Easy identifications

Human vs. Non-human But what if you come across bones like these? But what if you come across bones like these?

Human vs. Non-human Humans: bipedal Humans: bipedal Pelvis is broad and shallow (bowl-shaped) Pelvis is broad and shallow (bowl-shaped) The femur is the longest bone in the body with a single linea aspera 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 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 Long and narrow foot with multiple bones for bipediality Other mammals: Quadrupedal (mostly) Other mammals: Quadrupedal (mostly) Pelvis is long and narrow Pelvis is long and narrow The femur is short relative to the body size. If the femur’s 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 femur is short relative to the body size. If the femur’s 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. 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 Legs of larger mammals are modified toes and fingers for speed and agility

Human vs. Non-human Humans: Humans: Large, broad and flat vertebral body Large, broad and flat vertebral body Short spinous process (2-3 inches at the most) 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 Sacrum is triangular in shape and composed of 5 fused vertebrae, which are broad compared to length and flattened anteriorly-posteriorly Other mammals: Other mammals: Small vertebral body, often convex on one side and concave on the other Small vertebral body, often convex on one side and concave on the other Long spinous process (>6 inches in some larger mammals) Long spinous process (>6 inches in some larger mammals) Sacrum is long and narrow with fewer fused vertebrae (3-4) Sacrum is long and narrow with fewer fused vertebrae (3-4) Vertebrae

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

Human vs. Non-human Juvenile Remains Juvenile Remains The most common human bones to be mistaken for animal bones are bones from infants. 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 The ends of the long bones, bones of the hands and feet and clavicle are not fused These unfused bones have indistinct edges These unfused bones have indistinct edges Multiple ossification centers and unfused epiphyses increase the number of bones in infants and children 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 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 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 it’s dense nature, often survives burial better 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 it’s dense nature, often survives burial better Can be confused with smaller mammals such as raccoon, rabbit or even bird Can be confused with smaller mammals such as raccoon, rabbit or even bird

Human vs. Non-human

Mandibles from infants Mandibles from infants Petrous bones circled

Human vs. Non-human Human infant and fetal bones, recovered from a burial Human infant and fetal bones, recovered from a burial

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 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 macroscopically by morphology** Ids can be done microscopically (histological examination) Ids can be done microscopically (histological examination) **For our purpose, we only need to discuss macroscopic analysis

Human vs. Non-human Skull Fragments? Skull Fragments?

Human vs. Non-human Fragmentary and burnt bison bones. Fragmentary and burnt bison bones.

Human vs. Non-human Traumatized and burned pig bones

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

Human vs. Non-human Review: Review: Ask first, “Is it bone?” 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?) 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) 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 If in doubt, no matter how much, GPS, photograph and document the remains, then collect or call me or the on-call investigator

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