|MadSci Network: Genetics|
The size and shape of an individual is determined by their genes, as well as by the environmental conditions that they have grown up in. It is difficult to say whether environmental or genetic conditions are more responsible for the stature of many Asian populations. Different body sizes have different benefits associated with them. Bodies will adapt themselves to their environment in a number of ways. People growing up in hot climates tend to have longer bodies and limbs to get rid of excess heat. People in cold climates tend to have shorter broader bodies to hold in heat. (Bergman's Rule and Allen's Rule). Being smaller is, in general, more energy efficient, can make locomotion over different types of terrain easier (think of the mButi, or "pygmies", that live in dense forest in Central Africa) and a shorter height means less weight and a lower center of gravity, which means that injuries may be overall less likely to occur. (Especially from bonking your head on things.) The height of Asians may be a product of what sizes were beneficial to their ancestors in environments that shaped them. How large a person grows is also related to nutrition and health. In many underdeveloped countries of the world, people do not get as much to eat and are subject to less sanitary conditions, without healthcare. When people don't have plenty of food or are lacking certain key nutrients, they don't have the abundance of energy necessary to grow larger, especially when they are constantly fighting off sickness caused by living in unhealthy circumstances. Over the last century, many Asian (and other) populations have gotten taller due to changes in their diets, especially when they eat more protein. But obviously not all Asians are living in impoverished circumstances. So in short, (so to speak) body size has to do with how an individual has adapted to different stresses (or lack thereof) in their environment, coupled with any genetic predisposition for a particular body shape and size. For a much more in depth look into this issue, check out this website: http://www.unm.edu/~kimhill/101/lect3/lect3.html
Try the links in the MadSci Library for more information on Genetics.