Why Are They Small?
The pygmies of today all live in the African forest. People who live in tropical forests, where the climate is very humid, are generally very small. Examples are the peoples of southern India, Indonesia, the Philippines, and New Guinea, as well as the Maya of Central America and the inhabitants of the Brazilian tropics. The pygmies, though, are the smallest of all.
The climate of the equatorial forest is unusual - similar to that in a greenhouse, it is not very hot, but humidity stays around 100 percent. Although it is not very warm, the humidity is so high it prevents the body from shedding internal heat. Under normal hot conditions with lower humidity, one sweats intensely, which helps cool us down since perspiration chills as it evaporates. The same mechanism is used to keep food cold: A special fluid evaporates in a dosed container, absorbing heat from the inside of a refrigerator. It then returns to its liquid state, only to be evaporated once more, in a continual cycle.
But near 100 percent humidity, the body's normal ability to cool down is hampered or stopped completely. If perspiration does not evaporate, it does not cool the body. In such critical conditions, we risk overheating, with the body temperature rising above the normal 98.6 degrees Fahrenheit or passing the survival limit of 107 to 108 degrees. Heatstroke may be fatal and we must protect ourselves in some other way.
Pygmies sweat a lot, but not enough - it is their small stature that protects them, in two ways. First, the surface area of a small body is greater in relation to its volume. It is a mathematical fact: if cube A in Fig. 1.4 is 1 centimeter along each side and cube B is 2 centimeters, then A's surface area is one-quarter that of B, but its volume is eight times smaller. Heat is produced in the mass of the body, particularly in the liver and muscles, and is lost through the surface; if the latter is larger relative to body mass because a person is small, heat loss is easier and cooling more efficient. In a warm and humid environment, it is best to be small.
Second, small stature is an advantage if a person must use a lot of energy, since less energy is needed to move the small person's body weight. Athletes can produce large amounts of heat - marathon runners, for example, have to sustain intense muscular effort over a long period; they are usually relatively short, although it may seem better to be tall because of the longer stride. Pygmies use less effort to move than a larger people because the weight they have to shift is smaller.
Similarly, ponies are more efficient than large horses in terms of the energy produced from the food consumed. You need a big horse to shift a large load; but for traveling or drawing a small cart, a small horse or even a donkey will do. In the nineteenth century, U.S. transport companies used pack horses, but express mail delivery was performed by ponies.
Small stature, therefore, would appear to be an adaptation to life in the forest, which may have taken many years or only about three to five thousand. If, as some say, the tropical forest did not exist five thousand years ago, it may be that the pygmies adapted over this period. It is, however, possible, and I believe probable, that the forest already existed and that the pygmies have been there much longer. There are no fossils as proof, and we do not know enough about the climate in other times to be sure.
Although their bodies are small, the pygmies' heads are the same size as ours. The torso is muscular, and the arms and legs are slim and tapered. Their legs are rather short, but the overall effect is graceful. They are athletic: the men can climb trees one hundred or more feet with amazing agility.
They have elongated eyes and the widest nose in the world, also an adaptation to the forest. Small nostrils are useful when it is cold, since air has time to heat up before it reaches the lungs. In the forest, however, the air is warm and humid; there is no need to alter temperature and humidity through the filter of the nose, so wide nostrils are better.