Hair grows in the skin from a small hole called a hair follicle. In this hole, hair cells reproduce and push out the older ones. The older hair eventually falls out, and the newer hairs are added to the root of the hair. The follicles are made up of layered cuticle cells and a bulb at the bottom. A micrograph of the hair shaft shows that the cells are surrounded by a keratin matrix.
Hair is the most common trace material and may be the only forensic evidence. The condition of hair can reveal the “history” of a crime scene. If the hair is follicle-tangled or ripped, it may be a weapon, or it could be a sample of the victim. Not analyzing hairs, however, limits crime scene analysis and leaves important questions unanswered. Therefore, hair examination is vital to identify the source of a murder.
Human beings have several types of hair, referred to as lanugo. These hairs develop on the body during the third or fourth month of fetal life and fall off shortly after birth. All mammals have hair of some sort. Adult whales, elephants, rhinoceroses, and sirenians have sparse, scattered bristles. Humans have hair on most of their body. The only exceptions are the undersides of the fingers and palms.
Some studies have suggested that the origin of human hair is derived from the common ancestor of mammals, the synapsids. However, most synapsid fossils do not reveal soft tissue, so hair acquisition can’t be that far back. However, if hair were discovered on the bones of hominids, the age at which it appeared would have been 299 million years ago. In addition, hair may have been used as a symbolic sign of sexual maturity.
The follicles in our hair determine the texture and color of our hair. Hair can be straight or curly. Some people have curly or wavy hair, and others have very light or dark skin. Despite our genetics, we are often born with a color that resembles our parents. Hair type is also determined by the shape of our hair follicles. Some people are born with naturally curly hair, while others are born with thick and coarse strands of hair.
Melanin in hair is what gives our hair color. A darker pigment gives hair a more dark color, while a lighter one is white or gray. Melanin decreases as we age, and hair becomes gray or white. The pigment is not completely lost, but it can be weakened by stress. In some cases, a stressful event or hormonal imbalance may trigger this affliction. Hair can also be tested for DNA to determine paternity.