Have humans finally reached peak height?

Exactly what that upper height limit is appears to vary among countries. Different nationalities, even ones that seem to have peaked, do so at different heights. For example, while the men of Scandinavian countries appear to be approaching an average height just north of 180 centimeters, Japan’s men topped out nearly 10 centimeters below that, despite plateauing in the 1960s, among the earliest of any country in the study.

So what explains the differences? At the population scale, average heights have likely been increasing thanks to nongenetic environmental factors, like maternal size, nutrition, and access to health care. It is therefore not terribly surprising that the world map of heights seems to correlate pretty closely with gross domestic product—higher income increases access to better food and quality health care, which in turn makes a population healthier and eventually, taller.

What these findings indicate, in part, is that there may be a convergence point, a limit in human height under these preferable conditions—a biological asymptote.