Skeletons and written records show that human beings today are inches taller than humans just a century or two ago. And yet even today average heights vary among different nationalities, even among genetically homogenous populations, like the South Koreans and North Koreans. (South Koreans are taller.) John Komlos, professor of economics at the University of Munich and a pioneer in studying human well-being through history, explains what governs human height, and why some populations are taller than others.
Q: Why are people taller today than yesterday?
A: There are two main reasons. One is that the diet has improved considerably. In spite of some very negative aspects of the diet of industrialized populations, we have much better vitamin, mineral and protein intake than 100 or 200 years ago. As a consequence the body can grow much better.
In addition, our health has improved considerably along with medical technology. We have fewer endemic diseases, and fewer epidemic diseases. That is important because an incidence of disease usually means that the nutrients we do consume are not absorbed by the body sufficiently. Diseases lay a claim on our energy intake, so that there is not enough left over for the body to grow. These two factors play a considerable role.
We have been increasing in height for about 140 years. Prior to that, there were cycles in height, depending on economic circumstances and agricultural productivity and so forth. We were relatively tall in the Middle Ages, when population densities were relatively low and food supplies were still fairly adequate. The low point was in the 17th century. Frenchmen, for example, were about 162 cm on average [not quite 5 ft. 4 in.], which is extremely small. Only since about the middle of the 19th century has there been a general trend upwards.
The American population was the tallest in the world from about the American Revolution to World War II that's a long time. (There is a genetic component to [population] height, but there is very little genetic difference between European populations or their overseas offshoots.) America had a very resource-rich environment, with game, fish and wildlife. In fact we have data on disadvantaged people in America, such as slaves. They were obviously among the most mistreated populations in the world, but given the resource abundance and given the fact that the slave owners needed their work they had to be fed relatively decently. So slaves were taller than European peasants. It's no wonder that Europeans were just flooding to America.
[Americans today are no longer the tallest people in the world.] After the Second World War, many Western and Northern European countries began to adopt certain favorable social policies. There is universal health insurance in most of these societies that, of course, makes a difference in health care. You can also consider income inequality in America, since people who are at the low end of the totem pole have considerable adversity making ends meet. I suspect the difference [in height between Americans and Europeans] is due to both diet and health care.
Americans today suffer from an additional problem: obesity. If children are too well nourished, then they're not able to grow optimally. There are certain hormones that control the onset of the adolescent growth spurt and the onset of adolescence. Nutrition is one of the factors, along with genetic and hormonal ones, that are associated with the onset of puberty. Overnutrition prior to adolescence may affect the hormonal system and may produce too much growth hormone prior to puberty, so that sex steroids are produced earlier. And if that comes too early, then the youth will peak out sooner, and will not become as tall in adulthood as someone who had better nutrition. Also, the overload of carbohydrates and fats in a fast-food diet may hinder the consumption of micronutrients essential to growth.