How hair is formed is important to understanding cause and treatment of hair loss. We know that genes can play a large part in some kinds of scalp hair loss. Genes involved in the formation of hair follicles and their influence can be seen early in the development of an embryo (see Hair Science: How and Why Hair Grows).
Genes have a long evolutionary history (see Hair Science on the Cutting Edge). It all starts at the beginning. After the hair follicle is formed in the embryo, it continues to acquire the signaling pathways it will need to produce, maintain and cycle hair for its lifetime. Production of hair requires synthesis of the proteins (keratins) and other molecules from which a hair is constructed, patterned (straight, wavy, curly, frizzy) and pigmented (blond, red, brown, black). (see Hair Science: How and Why Hair Grows).