Living Conditions Have Improved For Us All, So Why Are Men Growing Twice As Fast As Women?

“To put this in perspective, about one in four women born in 1905 was taller than the average man born in 1905,” Lewis Halsey, a professor of environmental physiology at the University of Roehampton and one of the authors of the new paper, told The Guardian. But “this dropped to about one in eight women for those born in 1958,” he said.

Using data from the World Health Organization, various studies from the UK, and Wikipedia (the authors claim to have verified the sources cited and excluded those they deemed “less reliable”) Halsey and colleagues analyzed the changes in height and weight against two different variables: time, and human development index, or HDI. The latter attribute is “a measure of national levels of human well-being,” the team explains in the paper; “Individuals living in countries with low HDI scores are more likely to suffer from infectious diseases, chronic poor nutrition and larger overall disease burden than are individuals living in countries with high HDI scores.”

In other words – given the improvement in living conditions over the past century – these are two different ways of looking at the same thing: how do human bodies change as our environments improve? 

From that perspective, this study suggests far more than just a difference in how much men and women have changed on average. Rather, it adds weight to a long-standing idea that women are “more ecologically constrained” than men, Michael Wilson, a professor of ecology, evolution and behavior at the University of Minnesota who was not involved in the study, explained to the Guardian – possibly due to the demands of pregnancy and childbirth. 

“Investment in greater body size by males appears to be sensitive to nutritional conditions,” Wilson said. “When men grow up with more energy-dense food, they grow bigger bodies, to a greater extent than women.”

This effect could be compounded by the impact of sexual selection. Of course, we all appreciate a Short King, but “There seems to be an almost universal agreement among men and women that they would prefer to be in a relationship where the man is taller,” Abigail Weitzman, lead author of a study investigating the link between men’s height and their success in love, told the Washington Post in 2014.

Their tall genes, therefore, get pushed into the next generation, increasing the height of the species over time – but the new study suggests something more subtle, too. Since being taller and bigger is related to an easier, more bountiful life, a man’s height could act as a sort of proxy for how successful his offspring will be, Halsey told the Guardian

“Women can find men’s height attractive because, potentially, it makes them more formidable, but also because being taller suggests they are well-made,” he said. “As they’ve grown up, they haven’t been affected by the slings and arrows of a bad environment.”

Of course, that’s mostly supposition – the authors are keen to point out that, by its very nature, the study can only show correlation, not causation. Future studies, which track subjects based on their level of exposure to environmental stresses, might be able to further pin down the potential link between living well and growing big.

But for now, it’s a plausible theory. Big, tall men could be more successful in love not purely for the aesthetics of their body, but because “they’ve reached more of their height potential,” said Halsey.

“It’s an indicator that they’re well-made.”

The study is published in the journal Biology Letters.