from the pages of Discover Magazine, October 2015,

The height of an average Dutchman has increased nearly 8 inches over the past 150 years. By comparison, the average American male’s height grew only about 2.5 inches over that same period. Dutch people are now, on average, the tallest in the world. Researchers credit all those inches to a number of factors, including heavy consumption of dairy products, universal health care and natural selection.

So I decided to check Google. The average world height of an adult male is 5 feet 6 inches, the average American white male is 5 ft 10 in.

Wikipedia shows the following by Country
Netherlands 6 ft
Norway, Sweden 5 ft 11.5 in
Denmark, Finland, 5 ft 11 in
Ireland, Russia 5 ft 10 in
Canada, U.S. 5 ft 9 in
China 5 ft 7 in
Cuba, Mexico, South Africa 5 ft 6 in (right on that average)
Vietnam 5 ft 5 in

The only gene so far attributed with normal height variation is HMGA2. Genetically speaking, the heights of mother and son and of father and daughter correlate, suggesting that a short mother will more likely bear a shorter son, and tall fathers will have tall daughters.

Today the tallest race of humans is the Nilotic peoples of Sudan such as the Dinka they have been described as the tallest in the world, with the males in some communities having average heights of 6 ft 3 in and females at 5 ft 11 in.

This doesn’t agree with the Discover Magazine exactly. According to Discover Magazine, 150 years ago, the Dutchman were 8 inches shorter, making them 5 ft 4 in. To grow 8 inches (12 %) on the average in only 150 years makes me wonder if perhaps immigration didn’t also have something to do with it.