In the modern view, the external differences between the various races due to the peculiarities of natural and geographical conditions. That is, the outward signs of the people of any race are the result of adaptation to the conditions of the climate in which they live. Negroid (or rather - Negro-Australoid, or Equatorial) race is formed in the tropical climate of Africa, South and South-East Asia, Oceania and Australia. In these places people are in hot, humid climates and high levels of ultraviolet radiation. External signs of negroidal - evidence of how this race has adapted to this climate.
1. The hard hat curly hair to protect them from solar radiation.
2. Dark skin is a result of the high content in the skin and also in hair and retina) of the pigment melanin, which protects the skin from harmful ultraviolet damage.
3. Wide nostrils necessary for intensive heat transfer in the process of breathing.
4. And what about the lips? The fact that the thicker lips, the larger the area of the mucous membrane through which evaporates excess moisture.