Why do we have apocrine and sebaceous glands?

Abstract

The secretions of sebaceous and apocrine glands fulfil an important thermoregulatory role in cold-stressed and heat-stressed hunter-gatherers. In hot conditions the secretions emulsify eccrine sweat and thus encourage the formation of a sweat sheet and discourage the formation and loss of sweat drops from the skin. In colder conditions sebum changes its nature and repels rain from skin and hair.