Study shows why women have grown at half the rate of men in past century
Women around the world have increased their height and weight at half the rate of men over the last century, widening the physical gap between the sexes, new research finds.
For the study, titled 'The sexy and formidable male body: men’s height and weight are condition-dependent, sexually selected traits', a team from the University of Roehampton used data from the World Health Organisation, UK records and overseas experts to examine sexual size dimorphism – or the difference in height and weight between men and women – in relation to living conditions over the years.
Quality of life was measured by the human development index (HDI), a number based on life expectancy, time in education and per capita income, and falls between zero and one.
Dizzying heights
Professor Lewis Halsey and his colleagues found that, for every 0.2 point increase in HDI, women were on average 1.7 cm taller, while men were 4 cm taller, showing that men's height increased twice as fast as women's.
The researchers also looked into past height records in the UK where HDI rose from 0.8 in 1900 to 0.94 in 2022. From 1900-1950, average female height increased 1.9% from 159 cm (just over 5"2) to 162 cm (5"3), while average male height grew 4% from 170 cm (5"6) to 177 cm (5"8) – 2.76 times more than women's.
To illustrate this more clearly, Professor Halsey explained: 'About one in four women born in 1905 was taller than the average man born in 1905, but this dropped to about one in eight women for those born in 1958.'
A weighty issue
For every 0.2 point increase in HDI, women were on average 2.7 kg heavier, while men were 6.5 kg heavier, again indicating a disparity of over 200% in weight increase between the sexes.
Professor Halsey and his colleagues theorised that women's appetites may have fed the trend for more muscular, taller men, although with obesity a growing issue heavy did not necessarily equate to muscularity. They found that variability in weight was greater in nations with higher HDIs, probably because richer countries had access to more energy-dense processed foods, leading to weight gain in certain individuals.
Why the shortcomings?
Overall, the team suggested that a combination of improved social and environmental conditions, including reductions in disease, and sexual selection could be responsible for the disparity. They thought 'it was clear' that men were more sensitive to living conditions when it came to physical development.
Evolution has favoured traits such as stature and build in men, indicators of health and vitality. While height could also be considered 'more formidable', said Halsey, it also signals that 'they've reached more of their height potential' as they haven't been impaired by 'a bad environment'.
Michael Wilson, professor of ecology, evolution and behaviour at the University of Minnesota, commented the faster increase in male height and weight was 'striking'. He noted it was consistent with the notion that females are 'the more ecologically constrained' sex because of the demands of reproduction, particularly in mammals where pregnancy is 'energetically expensive'.
'Investment in greater body size by males appears to be sensitive to nutritional conditions,' he said. 'When men grow up with more energy-dense food, they grow bigger bodies, to a greater extent than women.'
The authors also thought they could have overstated sexual size dimorphism across countries, because their results may have been affected by different populations' maximum potential height for men and women. However, they believed the findings were accurate given that there was a very great sexual size dimorphism when they looked at just one population and country (the UK).
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