Racial Classification Based on Skin Colour
Racial classification is based on various physical traits, with skin colour being a major criterion. Globally, people can be broadly grouped into three categories based on skin colour:
(i) Leucoderma (White-skinned): Includes Europeans, Western Asiatics, North Africans, and Polynesians. Skin tones range from pinkish-white to light brown.
(ii) Xanthoderma (Yellow-skinned): Mainly includes Asiatic Mongoloids, some Amerinds, Bushmen, and Hottentots.
(iii) Melanoderma (Black-skinned): Includes Negroids, Papuans, Melanesians, and Pre-Dravidians.
Skin Structure and Pigmentation: Human skin has two layers – epidermis (outer) and dermis (inner). Skin pigment called melanin is present in the epidermis. The amount of melanin granules determines skin colour.
Climate and Skin Colour:
(i) Dark skin offers protection against intense sun rays and prevents excess Vitamin D production, reducing risk of sunburn and skin cancer.
(ii) Light skin is suited for cold climates and aids Vitamin D production.
Exposure to sunlight increases melanin production, making skin darker. People in forests or hilly areas receive less sunlight and thus tend to have lighter skin compared to those in open plains.