Why is man getting bigger and bigger?

The size of a person is determined by two things: the “environment” and the “genes”.

By the environment is meant: nutrition of the mother during pregnancy and lactation, and nutrition of the child until adolescence (when growth stops). An optimal diet does not only contain sufficient calories, but also sufficient proteins, minerals and vitamins. Only with an optimal diet can one reach the maximum length that is genetically fixed, ie in the genes that one has inherited from one’s parents. In addition to nutrition, better hygiene and medical care also play a role. They are all much better in our regions now than they used to be, and that is why there are now more grown-ups than there used to be.

Doorways are made according to the average dimensions of people. Since there are more tall people than before, we are on average taller than before and doorways are thus made higher.

As for the genes that determine our maximum size, they may have evolved effectively to allow for greater heights. That doesn’t necessarily have a direct benefit. The pygmies and bushmen, for example, show that it is rather an advantage to have a shorter stature because the hunters can walk better in forest or undergrowth or because they are less visible to their prey in long grass.

But taller stature in our ancestors is thought to have been selected by a female preference for taller males – this is called sexual selection. If taller men were more successful in finding mates, they will have given birth to more children than shorter men. The genes that allow for a larger size, and that are passed on to the children, will therefore become more abundant in the population in the long term and supplant the “short genes”. Result: people have grown taller on average.

It seems that our modern women still prefer tall men instead of short ones!

Incidentally, the described evolution through sexual selection could only take place in communities where women were allowed to choose their partner themselves. In communities where the parents chose a partner for their daughter, this mechanism could not come into play (unless the women subsequently “cheated”).