The “secular change” refers to the phenomenon that the physical characteristics of the human body changes in a long period of time compared to the human longevity. The most well observed secular change is that of the stature. In many countries in the world, stature has been increasing in last 100 years.  Figure 1 shows the changes in the mean stature of adult male Japanese in Kanto region from Jomon Period (until about 300 BC) to present. The mean stature decreased since the Kofun period (250 AD to 538 AD), and was the lowest at the end of Edo period (1603 – 1867). Since then, it increased very rapidly.

The rapid secular changes have also been observed in European countries, and there is evidence that the secular change has ceased in the Netherlands and North European countries.
Since the pattern of secular change in stature follows that of environmental factors relating to the nutritional status, the main cause is considered to be environmental rather than genetic.