Over a period of 100 years, men's height and weight have increased twice as much as women's, which has made the physical differences between the sexes greater.
This is stated by researchers at British Roehampton University in a new study.
With the help of data from the World Health Organization (WHO), the researchers have investigated how people have become larger as living standards have increased. The latter is based on the UN's Human Development Index (HDI), which with a figure between 0 and 1 provides a measure of different countries' average life expectancy, education level, and income per capita.
Fell to one in eight
Based on statistics from 62 countries, it is found that for every HDI increase of 0.2, women have on average become 1.68 centimeters taller and 2.7 kilograms heavier – while men have grown by 4.03 centimeters and 6.48 kilograms.
About one in four women born in 1905 was taller than an average man, but this fell to one in eight women among those born in 1958, says Professor Lewis Halsey to The Guardian.
"More formidable"
In the study named "The sexy and formidable male body: men's height and weight are condition-dependent, sexually selected traits" – the researchers also argue that sexual selection governs the size difference between the sexes. That women simply prefer tall and muscular men.
Women may think that men's height is attractive because it potentially makes them more formidable, but also because it indicates that they are well-built. Since they have grown tall, they have not been affected by a poor environment and have reached more of their potential height, says Lewis Halsey to The Guardian.
"There is a ceiling"
Patrik Lindenfors, a researcher in biological and cultural evolution, affiliated with the Institute for Futures Studies, thinks the study is interesting.
Men's growth is more sensitive to environmental impact. It's easy to understand, since women need to conserve resources to be able to go through pregnancy, while men can put everything into growth, he says.
But will men continue to grow at the same rate?
No, there is an upper ceiling. If you get more food, you have a greater potential to become larger, but it's not an evolutionary change, it's environmental. It means there is a ceiling for how big you can become, and it's genetic.
