The Dutch are, on average, the world's tallest people, but it hasn't always been that way.

In fact, 150 years ago they were almost three inches (7.5cm) shorter than the average American.

So what happened? Scientists believe a number of factors are responsible, such as genetics, better diet and medical care.

But now there's another theory. Research from the London School of Tropical Medicine suggests that natural selection may also have something to do with it.

Jane O'Brien went to the Netherlands to find out more.

Edited by Bill McKenna; Filmed by David Botti

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