What Makes Humans Grow Tall?
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Demographics
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Human beings started out as relatively compact organisms and grew taller as they adapted to standing upright. Certain demographic factors have contributed to human height. Population density appears to minimize the increase in height from one generation to the next; people were taller in the Middle Ages when population was sparse. The Middle Ages were also a period of widely available food and other resources. By the 1600s, however, the population had grown, and land consumed by promogeniture. Over-farming and over-mining diminished Europe's resources. The average Frenchman was just a bit over five feet tall, shorter than his medieval predecessors. The Age of Exploration bloomed in 17th-century Europe for good reason; the population density was growing without resources or room to support it. As new frontiers opened and new resources developed, humans began to grow taller with each generation until today's Frenchman averages closer to six feet tall, and his New World relatives in Michigan are a few inches taller than their cousin.
Genetics
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The first gene linked to tallness in humans was isolated by researchers working in hospitals in association with Harvard and Oxford Universities. Humans inherit a copy of the HMGA2 gene from each parent. A specific form of the gene can add a little over an inch to the child, while inheritance of two of the genes can add about two and a half inches to the child's adult height. Other genes that affect height are associated with gigantism, a condition in which the entire body grows to be exceptionally large, and dwarfism, in which certain bones grow in a way that result in an unusually short human being.
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Nutrition
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Growing tall is the result of more than just genetics and demographics, though. The allocation of resources that results in proper nutrition (including protein for muscle and calcium for bone density) has been a major factor in the growth spurt that humanity has enjoyed for the last century and a half. Studies, including one at Princeton University and an ongoing survey by the Centers for Disease Control, have focused on the correlation between adequate nutrition on human height and health. Improved health spots and corrects endocrine system problems and nutritional deficiencies to keep children growing strong. For the last half of the 20th century, Americans, with a bountiful supply of food and best health care, were the tallest people in the world, regardless of genetic heritage or how crowded the city they inhabited. Today, several Scandinavian countries outgrow Americans. Two factors, overnutrition and obesity, may play roles in the slowdown. Over-consumption of vitamins and proteins appear to trigger the early onset of puberty, "topping out" adolescents at an earlier age. Obesity resulting from a high-fat and complex-carbohydrate-heavy (as in "fast-food") diet may limit the intake and inhibit the absorption of nutrients and trace elements needed for growth. Nutrition and health care may provide the key to human growth in an increasingly interdependent world.
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- Photo Credit Public Domain, DRW & Associates, Inc
