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Tuesday
Jul102012

Forensics 101: Race Determination Based on the Skull

The three key factors required to identify skeletal remains are age, sex and race. In previous Forensics 101 posts I’ve reviewed age estimates of an adult versus a pre-pubescent victim, age estimates based on epiphyseal fusionadult age based on the pelvis, and sex determination based on features of the pelvis and skull. The final aspect of general skeletal identification is race.

Physical anthropology considers that there are six main races—black, white, American Indian, East Asian, Polynesian and Melanesian/Australian, but for simplicity’s sake, we’re only going to consider the first three as they are the most comprehensively described.

Racial differences in skeletal structure originally arose when small genetic changes developed in populations isolated by geography. Now, as world travel increases and people of different racial backgrounds intermix and produce children, it is becoming harder to differentiate individuals of different races. But there are some key features of the skull that can help forensic anthropologists:

  • Mouth: Whites tends to have smaller teeth, often with significant crowding and impacted third molars, and frequently exhibiting an overbite. Blacks rarely have crowding and the upper teeth often project outwards due to the angled shape of the maxilla. American Indians have well spaced teeth but often exhibit sclerosed dentition—when calcium deposits build up inside the tooth, thinning the root canal—leaving teeth loose within the mandible and easily cracked.
  • The palate and palatine suture:  The hard palate is the bony structure at the top of the mouth bordered by the upper teeth. In American Indians, the palate is elliptical, with the ‘U’ shape angling in at the back teeth. In blacks, the palate is hyperbolic—a perfect ‘U’ shape with straight lines. And in whites, the palate is parabolic with the ends of the ‘U’ flaring outwards. The transverse palatine suture that horizontally transects the palate also varies by race: It is straight in American Indians, curved in blacks, and a jagged line in whites.

 

  • Incisors: The shape of the incisors is the most important indicator of race in the teeth. In American Indians (and East Asians, both of Mongoloid ancestry), the incisors are shovel-shaped, named because the inner surface is scooped or curved. Black and whites both have blade-form incisors where the tooth has a flat profile.
  • The nose: The nose provides multiple race indicators. In whites, the nasal aperture is long and narrow, with a high bridge and a sharp nasal sill (the lower edge of the nasal aperture projects sharply outwards). In blacks, the nasal aperture is short and wide with a low bridge and a guttered or trough-like nasal sill. In American Indians, the nasal aperture is medium-sized with both a medium bridge and nasal sill.

 

  • The mastoid process: The shape of the mastoid process differs between the races. In blacks, the bony projection is wide, in whites it is narrow and pointed, and in American Indians, a secondary smaller projection forms on the back surface of the mastoid process.

 

Rarely do all of these indicators point firmly to a single race. Instead, it is the story told by the majority of physical characteristics that suggests the victim’s ethnic background. If in doubt, additional post-cranial (skeletal features in the rest of the body) can help indicate race as well.

The information gathered by a forensic anthropologist concerning age, sex and race can lead criminal investigators to a narrowed missing persons search and hopefully to a definitive victim identification.

Illustrations: Gray’s Anatomy

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