You've probably noticed, either from museum exhibits or visits to colonial houses, that humans these days are generally taller than we used to be. In fact, over the last 150 years, the average height of people in industrialized nations has increased approximately 10 centimeters (about four inches).  In the first half of the 18th century, the average height of an English male was 165 cm (5 ft 5 in) and the average height of an Irish male was 168 cm (5 ft 6 in). American men at the time were taller. By the following century, they'd have an extra 3-9 cm on their European counterparts. These days, the male population in England measures in at 175.4 cm (5 ft 9 in) while the U.S. still has them beat with an average height of 177.6 cm (5 ft 10 in).

When you consider all of human history, this species-wide growth spurt is actually a rather new phenomenon. Prior to that, average heights were variable based on particular environmental and socioeconomic factors. For example, low population density during the Middle Ages meant abundant food and, consequently, taller people.

But are people still getting taller? Will we eventually have to rebuild all our infrastructure and raise the height of basketball hoops? Most likely not. Our increasing height seems to have leveled off lately, and while there will always be outliers, this is probably as tall as we get as a species. To understand why that is, we have to first understand why we started growing in the first place.

The answer is relatively straightforward and harkens back to the Middle Ages example. Easier access to better food and healthcare since the mid-1900s have allowed people to develop to their full physical potential. Modern science and technology led to improvements in childhood nutrition and fewer childhood illnesses, which also drove height up. This is corroborated by the fact that historically, conditions of poor access to sufficient food are well correlated to shorter populations.

But now that most people in industrial countries are not suffering from malnutrition or epidemics, the human population has settled at a relatively stable average height. Which is probably good for architects and basketball hoop manufacturers.