The Dutch are currently the tallest people on Earth, reports a new study, due to natural selection as well as good environmental conditions in the Netherlands.
Since there is a connection between height and lifespan -- with taller individuals tending to live longer than shorter people -- lessons can be learned from the Dutch.
Most Dutch enjoy "low social inequality, good access to good health care (and) regular healthcare checks for children," lead author Gert Stulp told Discovery News. His team's research is published in the latest issue of the Proceedings of the Royal Society B.
Stulp, a researcher at the University of Groningen and the London School of Hygiene and Tropical Medicine, and his colleagues analyzed data from what's known as the LifeLines study. LifeLines has been examining the health and health-related behaviors of 167,729 people living in the Netherlands, covering several generations. The researchers also examined data on height over the past recent centuries.
In the mid-18th century, the average height of Dutch men was only about 5'4", based on military records. Now, the average height of men from the same region is over 6 feet. The average height of Dutch women is 5'8".
What's more, the Dutch are continuing to grow taller.
"The Dutch have shown a remarkable increase in height that has been rather linear with little evidence of leveling off, which itself suggests that the limit might not have been reached," Stulp said. "And further improvements in environmental quality may well mean that we see a further increase in height."
In contrast, some research suggests that people in the United States are now growing shorter on average. Currently, the average height of American men is about 5'10" and the average height of American women is about 5'4 ½".
"One reason may be the larger -- and increasing -- inequality in the U.S.," Stulp said. "Inequality leads to shorter heights, because the costs in terms of height of being poor are larger than the benefits of being rich."
He also said that natural selection could be favoring shorter heights in the United States. That isn't the case in The Netherlands, where the LifeLines study revealed that taller women experienced higher child survival. He explained that they could have more bodily resources to invest in their offspring.
Height was also consistently related to the number of children born, with taller people tending to have more kids.
Overpopulation and limited resources can keep human growth in check.
"Taller individuals require more resources, bigger planes, bigger beds and the like," Stulp said.
Not every region can therefore support such people, as a collective whole, over long periods.
Another factor is nutrition.
"A nice example may be the large quantities of milk and cheese products that the Dutch consume, which have been shown to have substantial effects on growth," Stulp said.
John Komlos, who has also studied human height, told Discovery News that he agrees with the primary findings of the new study, and pointed out that evolution by itself cannot explain what's going on in the Netherlands.
"If the tall Netherlands population was based on evolution, then why were they not already the tallest in the 19th century?" asked Komlos, who is a professor emeritus from the University of Munich.
"In other words," Komlos added, "the fact that they are the tallest today is due to their social policy: terrific health care provided for expectant mothers, social safety nets, etc. Otherwise, they would be only as tall as the British or Americans."