Asked by: Robert Craddock, by email
Height in humans is about 70 per cent genetic and 30 per cent environmental, but there are many different genes that all contribute to your final height. Women generally stop growing any taller around the age of 15, whereas men keep going for another three years. For this reason men tend to be taller than women, for a given set of height genes.
In a sense, you could say that the Y chromosome is itself one of those height genes. If a mother and father are the same height, their daughters will be roughly the same height, but their sons will be taller. This is because in order for the mother to be the same height as her husband, she must have more of the other ‘tall genes’ than him, and these get passed onto her sons. And often women marry someone slightly taller, which makes her sons taller still. For them to be shorter, she needs to marry someone much shorter than her, or there need to be significant environmental influences at work which serve to offset the genetic contribution.
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