Scientists try to answer why Dutch people are so tall
The Netherlands is the land of giants: on average, its women stand almost 1.71 metres (5.6 feet) tall, and its men 1.84 metres.
But how the Dutch became the world’s tallest people has been somewhat of a mystery. After all, two centuries ago they were renowned for being among the shortest. What happened since then?
A popular explanation is nutrition – a calorie-stuffed diet rich in meat and dairy products. But that can’t be the whole story, experts say.
Other European countries, too, have enjoyed similar prosperity and a rise in living standards, yet their citizens have not shot skywards as much. The average male height in the Netherlands has gained 20 cm (eight inches) in the last 150 years, according to military records. By comparison, the height of the average American man has risen a mere six centimetres over the same period.
Researchers led by Gert Stulp, a specialist in population health at the London School of Hygiene and Tropical Medicine, combed a Dutch database for clues.
Called LifeLines, the record contains exhaustive detail about the lives and health of more than 94,500 people who lived in the northern the Netherlands from 1935 to 1967. In this three-decade snapshot, the people who had the most children were tall men, and women of average height, the team found.
For example, the most fertile men were seven centimetres above the average height. Statistically, they had 0.24 more children on average than the least fertile men, who were about 14 cm below the average height.
Compared to counterparts in other countries where they often tended to have fewer children, taller women also reproduced more in the Netherlands. Many postponed having children until after their studies, but once they forged a successful relationship, often had a large family.
There seems to be a cultural preference as well.
Stulp pointed to figures showing that, in the United States, shorter women and men of average height have the most reproductive success.
“There is much variation in what men and women want,” he said. “When it comes to choosing a mate, height tends to have (only) a small effect, which is not very surprising given the many other, more important, traits people value in their mate.”
Dutch men are tall, and Dutch women apparently like it that way.
Scientists have found that natural selection—women choosing taller men to mate with—is a factor in the height of Dutch men, which has rocketed up by 20 cm (7.9 inches) over the past 200 years, while the heights of people in other similarly developed nations has—literally—only inched up.
In the mid 18th century, Dutch soldiers measured an average height of 165 cm (5 feet 4 inches). Back then, American soldiers “towered over” the Dutch by up to eight centimeters, according to research published today by the Royal Society in the UK.
But things have changed. Dutch men are now the tallest in the world, with an average man reaching 184 cm (6 feet). The Dutch are closely followed by Scandinavians, and are far taller than Americans, who have only grown by 6 cm (2.4 inches) over the same time period, to around 178 cm (5 feet 10 inches).
Taller than average men had more children overall, and more children that survived, while shorter men were less likely to reproduce.
Because tall men are likely to pass on the genes that made them tall, the outcome suggests that—in contrast to Americans—the Dutch population is evolving to become taller, Stulp says. "This is not what we've seen in other studies—that's what makes it exciting," says evolutionary biologist Simon Verhulst of the University of Groningen in the Netherlands, who was Stulp's Ph.D. adviser but wasn't involved in the current study. Verhulst points out that the team can't be certain that genes involved in height are actually becoming more frequent, however, as the authors acknowledge.
The study suggests that sexual selection is at work in the Dutch population, Stearns says: Dutch women may prefer taller men because they expect them to have more resources to invest in their children. But there are also other possibilities. It could be that taller men are more resistant to disease, Stearns says, or that they are more likely to divorce and start a second family. "It will be a difficult question to answer.”
Another question is why tall men in Holland are at a reproductive advantage but those in the United States are not. Stulp says he can only speculate. One reason may be that humans often choose a partner who's not much shorter or taller than they are themselves. Because shorter women in the United States have more children, tall men may do worse than those of average height because they're less likely to partner with a short woman.
Apparently the Dutch and Americans have different preferences
Stulp himself is Dutch and 6 feet 7 inches tall. But his parents are not especially tall.
"It must be all the milk [I drank]," he says.
Good diet is, in fact, a major factor in the stature of his countrymen.
"We have also the welfare state and an excellent health care system and we also have low levels of social inequality, which also has been shown to increase a nation's height," he says, "But our study also suggests that, on top of those things, natural selection may also have a role."
There is no concrete explanation for why taller Dutch people have more children. But Stulp has a few guesses.
"One reason might be that, for some reason, Dutch value height a little bit more in their partner," he says. "Height may [also] be associated to variables like health and income a little bit more strongly in the Netherlands or the United States."
He adds the data was controlled for ethnicity.
Asked if Dutch men, like himself, are simply more attractive mates, he demurred.
"Well, I have my own experiences, but it might have something to do with attractiveness indeed."