We all know the families populated by towering basketball players versus the petite households with builds best suited for, say, horse jockeying or wrestling. There’s probably a fair amount of height variation within friend groups, too: The tallest friend takes the selfies, while the shortest struggles to fit in the frame. But despite these drastic variations, humans pretty much fall within a normal height range: In the United States, healthy men are, on average, 5 feet and 9 inches tall while women are typically 5 feet and 4 inches. Thanks to middle school science class, we know that we inherit height from our parents. Why, though, do most people stay within these standard limits? Why don’t we all grow to be 10 feet tall?