Data from dozens of countries reveal that gender -size and weight differences increased during the 20th century. This has a name: “sexual dimorphism”.
- During the 20th century, the size and weight gains of men were more than twice higher than those of women, which increased sexual dimorphism of size.
- This has happened with the transnational and transgenerational improvement in living conditions, more precisely when the environmental stressors decrease.
- According to the researchers’ hypothesis, women’s preferences may also have fueled a trend towards larger and more muscular men.
“Sexual dimorphism.” This is the name given to a phenomenon described by researchers from the universities of Genoa (Italy), Missouri-Columbia (United States) and Roehampton (England) in a recent study. These are all the differences between the male and the female of the same species, apart from those of the sexual organs themselves. Observed in many species, sexual dimorphism “may result from the fact that the sexes occupy different food niches, that the larger females are more fruitful or that larger males have advantages linked to the choice of the female or to competition between males it is frequent in terrestrial mammals, including humans “, explained the team.
The more living conditions improve, the more size and weight increase
Indeed, men are on average larger and heavier than women in all countries, which probably reflects the evolutionary history of physical competition between men for status and control of resources. According to scientists, these size size dimorphisms are accompanied by vulnerabilities due to higher maintenance and development costs for sex with the largest size. “These costs comply with evolutionary theory which postulates that large, elaborate and sexually selected features are health and vitality signals, because exposure to a stress factor (for example, early disease) will compromise (for example, a shorter stature) more than other features. “
As part of the works, published in the journal Biology Lettersthe authors wanted to test this high -scale hypothesis in humans. The latter used data from the World Health Organization (WHO), foreign authorities and British archives to see how size and weight changed with living conditions. The human development index (HDI), a score based on life expectancy, the time spent in education and income per capita, which goes from zero to one, has been used. According to the results, for each 0.2 point increase in the HDI, women measured an average of 1.7 cm more and weighed 2.7 kg more, while men measured 4 cm more and weighed 6, 5 kg more. This suggests that as living conditions improve, size and weight increase, but more than twice as fast in men than in women.
The average size of men climbed 4 % against 1.9 % for women
In order to see if similar trends occurred within the countries, the researchers examined the historic size records in the United Kingdom, where the HDI went from 0.8 in 1900 to 0.94 in 2022. During the First half of the century, the average size of women increased by 1.9 %, from 159 cm to 162 cm, while the average size of men increased by 4 %, from 170 cm to 177 cm. “To put things in perspective, about one in four women born in 1905 was greater than a average man born in 1905, but this figure fell to around one in eight for those born in 1958”, told the GuardianLewis Halsey, who participated in research.
The team suggests that the preferences of women may have fueled a trend towards larger and more muscular men. “Stature and physique are first -rate health and vitality indicators, while sexual selection also promotes men who are more likely to protect and defend their partners and children against others.”
