Human height varies widely across the world. Men and women can be very tall or very short. Genetics, environment and certain medical conditions play an important part in how tall humans grow. According to Chao-Qiang Li, a molecular biologist at the U.S. Department of Agriculture Human Nutrition Center, 60 to 80 percent of height is genetic. Another 20 to 40 percent of height is attributed to environmental factors. A third factor is age. As we age, we tend to lose a few inches. Regardless of how tall you may grow to be, science hasn't made any definite pronouncement as to how tall human beings are capable of growing.
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There are a wide variety of factors that contribute to how tall a man or women becomes. Research has shown that genetics play a large role in height. Research indicates there's a strong correlation between the height of a mother and her son, as well as the height of a father and his daughter. Scientists have isolated a gene known as HMGA2. This gene is believed to contribute to height variations.
Diet, exercise and living conditions play a large role in determining the height of men and women. Those living in areas that are stricken with poverty, war or natural disasters are more likely to have a lower average height than those living in areas where the population is healthier. Ethnicity also plays a role in height. For example, males in China are -- on average -- 1 inch shorter than males who live in the United States.
More often than not, men are taller than women. While women have a tendency to grow and reach their full height at a young age, men frequently surpass women in height by the time they reach their early 20s. Sex chromosomal differences account for the differences in height. The XY chromosome -- male -- and the XX chromosome -- female -- play a large role in the height differences between males and females.
In a 2004 study conducted by the Centers for Disease Control and Prevention, the average height of men between the ages of 20 and 74 is 5 feet 9 inches tall. Women are an average of 5 feet 4 inches tall.
As of 2010, Sultan Kosen is known to be the tallest living man. According to the Guinness Book of World Records, Kosen measures in at 8 feet 1.047 inches. He was born in 1982 in Mardin, Turkey. Kosen is one of 12 individuals in the world who are confirmed to be over 8 feet tall. The world's tallest woman is De-Fen Yao of China. She stands 7 feet 9 inches tall. While never confirmed, Yao is thought to suffer from acromegaly. This disease is the result of a tumor on the pituitary gland. An acromegaly tumor can cause the pituitary gland to produce excessive amounts of growth hormones.