Human height is the distance from the bottom of the feet to the top of the head in a human body, standing erect. When populations share genetic background and environmental factors, average height is frequently characteristic within the group. Exceptional height variation (around 20% deviation from average) within such a population is sometimes due to gigantism or dwarfism, which are medical conditions caused by specific genes or endocrine abnormalities. In regions of extreme poverty or prolonged warfare, environmental factors like chronic malnutrition during childhood or adolescence may account for delayed growth and/or (in severe cases) marked reductions in adult stature even without the presence of any of these medical conditions.
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