Hair Identification
Animal Versus Human Hairs
Human hairs are distinguishable from hairs of other mammals. Animal hairs are classified into the
following three basic types.
• Guard hairs that form the outer coat of an animal and provide protection
• Fur or wool hairs that form the inner coat of an animal and provide insulation
• Tactile hairs (whiskers) that are found on the head of animals provide sensory functions
Other types of hairs found on animals include tail hair and mane hair (horse). Human hair is not
so differentiated and might be described as a modified combination of the characteristics of guard
hairs and fur hairs.
Human hairs are generally consistent in color and pigmentation throughout the length of the hair
shaft, whereas animal hairs may exhibit radical color changes in a short distance, called banding.
The distribution and density of pigment in animal hairs can also be identifiable features. The
pigmentation of human hairs is evenly distributed, or slightly more dense toward the cuticle,
whereas the pigmentation of animal hairs is more centrally distributed, although more dense
toward the medulla.
The medulla, when present in human hairs, is amorphous in appearance, and the width is
generally less than one-third the overall diameter of the hair shaft. The medulla in animal hairs is
normally continuous and structured and generally occupies an area of greater than one-third the
overall diameter of the hair shaft.
The root of human hairs is commonly club-shaped (figure 22), whereas the roots of animal hairs
are highly variable.
Figure 22. Photomicrograph of Human Hair Root
The scale pattern of the cuticle in human hairs is routinely imbricate. Animal hairs exhibit more
variable scale patterns. The shape of the hair shaft is also more variable in animal hairs.
Human Hair Classifications