Height is affected not only by one's own nutrition but also by one's mother's nutrition. Small mothers are more likely to produce small fetuses who are more likely to be small adults.
For example: a woman has a gene which means that, with good nutrition, she should be very tall. However she grows up during a famine and is therefore small. Because she is small, all her fetuses are relatively small (regardless of their genes).
So basically, the purely non-genetic, environmental factors affecting
your mother, also affect you. This means that it takes generations for
people to reach the full height which their genes give them the