Presence of hair is one of the most gripping features in mammals and those vary within species or mostly among animal groups. Differences and similarities of hair among species have been important in forensic studies. Katz (2005) defines the hair as an appendage of the skin that grows out of a hair follicle. It is a complex chain of proteins, mainly keratin, interconnected and formed fibrils. The outermost layer of a hair shaft is known as the cuticle, which is scaly and very different within species. Inside or the cortex of a hair shaft is also different in both inter and intra species as the medulla and pigmentation vary according to the localities. These features should be looked at in order to differentiate human and animal hair.
Hair grows everywhere on the human body except mucus membranes and glabrous skin (lips, penis, labia minora, palms, and feet). There are four types of human hair known as; primordial, lanugo, vellus, and terminal. Primodial and lanugo hairs occur before the birth inside the mother before three and six months respectively. Vellus hairs are distributed all over the body and they are fine and lack medullae inside cortex. Terminal hairs are prominent in appearance and hard in structure, present on the scalp / head, eye brows, eye lashes, face, armpits, and around genital organs. Mongoloids have the thickest terminal hairs among all the human races (90 – 120 µm). Caucasian hairs measure the diameter between 70 and 100 micrometres while, in Negroid race it is from 60 to 90 micrometres. There are two types of pigments, eumelanin and pheomelanin, that result in different hair colours according to the concentrations inside the cortex. In red hair, pheomelanin is prominent while eumelanin is dominant in black, blond, and brown hairs. Grey hair is a result of lowering or disappearing of pigments from the hair cortex. It is hypothesized that, straight hair in human evolved later in Caucasians and Mongoloids.
This exclusive feature has been a blessing for all the mammals to overcome heat and sometimes to win sexual mates but, some animals viz. Aardvark prefer scales over hairs. The animal hair are of three types; vibrissae, bristle, and wool. All those three types are very important for their lifestyles as they are incorporated with different functions. Vibrissae make the whiskers to function in tactile and sensitivity. Coat or guard hairs are made up of bristle hairs. Colours of bristle hairs vary within animal species and other taxonomic groups, giving the animals a distinctive appearance. Bristle colour is also inherited through generations, i.e. the coat colour patterns could vary among individuals (e.g. dogs and cats). Wool hairs are fine that make the fur of an animal, functioning as insulators (e.g. sheep, goat). The cuticle and the medullar patterns vastly differ among animals. The tail and mane hairs in horses are more like human terminal hair.
What is the difference between human hair and animal hair?
Hairs in mammals vastly vary in structure, colour, location on the body, present period of the life stages, and function. Sometimes the naturally inherited hair is removed or changed in order to attract others, which has been becoming extremely common among humans and mostly in females. Men usually shave or leave their facial hair and trim or grow their hairs on scalp for better presentation to the others. However, animals have not invented such techniques instead they have attractive coats to threaten others.