The origin of hair. The evolution of the trichocyte

is important in mammals for thermoregulation – the regulation of temperature that allowed mammals to adapt to a wide range of environments. Early mammals first appeared around 180 million years ago. They were able to be nocturnal, since their evolution of hair kept them warm during the cool night hours and increased the amount of time they could spend on activities such as hunting or foraging. The earliest known evidence of hair is actually the presence of whiskers – functional hairs used to sense the surrounding environment – on therapsids, mammal-like reptiles which existed around 290 million years ago and are known as the ancestor of modern mammals.