A new study has revealed the evolutionary reason why women tend to feel colder than men, something that not only happens with human beings, and that seems to be related to reproduction, according to an article published in the journal Global Ecology and Biogeography.
Researchers at the Faculty of Zoology at Tel Aviv University in Israel now offer a new evolutionary explanation for the familiar scenario in which women wear a sweater to work, while their male counterparts are comfortable wearing short sleeves in an office with air conditioning.
In addition, they concluded that this phenomenon is not unique to humans, since in many species of endotherms (birds and mammals) males prefer a cooler temperature than females.
“We propose that males and females feel temperature differently,” the researchers note. This is a built-in evolutionary difference between the heat detection systems of both sexes, which is related, among other things, to the reproduction process and the care of the young.
The study was led by doctors They were Levin and Tali Magory Cohen, from the Faculty of Zoology and the Steinhardt Museum of Natural History, Tel Aviv University, Yosef Kiat, from Haifa University, and Dr. Haggai Sharon, a pain specialist from Tel Aviv University Sackler School of Medicine and Tel Aviv Sourasky Medical Center (Ichilov Hospital).
Both researchers explain that “this difference in thermal sensation did not arise so that we could argue with our partners about the air conditioning, but rather the opposite: it is intended for the couple to take a certain distance from each other so that each individual can enjoy something of peace and tranquility ».
“The phenomenon can also be related to sociological phenomena observed in many animals and even in humans, in a mixed environment of females and males – they add -: females tend to have much more physical contact with each other, while the males maintain more distance and avoid contact with each other.
The new study included an in-depth statistical and spatial analysis of the distribution of dozens of bird and bat species living in Israel, along with a comprehensive review of the international research literature on the subject.
Dr. Levin, who among other things studies the physiology and behavior of bats, observed in his previous studies that during the breeding season males and females tend to segregate, with males inhabiting colder areas. For example, entire cave colonies on the slopes of Mount Hermon are made up of only males during the breeding season, while in the warmer part of the Sea of Galilee there are mainly females, who give birth and raise their young there. It was this phenomenon that piqued his curiosity.
Furthermore, a study of the research literature reveals several examples of a similar phenomenon that is observed in many species of birds and mammals. In migratory bird species, males spend the winter in colder areas than females (it must be taken into account that, in birds, segregation between the sexes takes place outside the breeding season, since the males participate in raising chicks).
Among many mammals, even in species that live in pairs or in mixed groups all their lives, males prefer shade while females prefer sunlight, or males ascend to mountain peaks while females remain in the valleys.
After reviewing the literature, the researchers conducted their own research. They sampled information collected in Israel over the course of nearly 40 years (1981-2018) on thousands of birds from 13 species of migratory birds from 76 sites (data from Birdlife Israel and the Steinhardt Museum of Natural History) and 18 species of bats from 53 sites (data from researchers and the Society for the Protection of Nature).
In total, the study included more than 11,000 individual birds and bats, from Mount Hermon in the north to Eilat in the south.
The reasoning behind the choice of birds and bats for the study is the fact that they fly and are therefore highly mobile, and the researchers hypothesized that the spatial separation between the sexes – which sometimes extends to different climatic zones- would be especially clear in these groups. Furthermore, Israel’s significant climatic diversity allowed them to study individual animals of the same species living in very different climatic conditions.
The results of the study clearly demonstrated that males prefer a lower temperature than females, and that this preference leads to a separation between the sexes at certain periods of the breeding cycles, when males and females are not needed, and even they can interfere with each other.
‘Our study has shown that the phenomenon is not unique to humans; among many species of birds and mammals, females prefer a warmer environment than males, and at certain times these preferences cause segregation between the two species, ”he explains.
‘In light of the findings, and the fact that it is a widespread phenomenon, we have hypothesized that it is a difference between the heat sensing mechanisms of females and males, which has evolved throughout evolution, ”he explains.
In this sense, he adds that «this difference is similar in its essence to the known differences between the sensations of pain experienced by the two sexes, and is affected by the differences in the neuronal mechanisms responsible for the sensation and also by the hormonal differences between males and females ».
Dr. Magory Cohen points out that this difference has several evolutionary explanations. First, the separation between males and females reduces competition for environmental resources and drives away males who can be aggressive and endanger the young. In addition, many female mammals must protect their young at a stage where they are not yet able to regulate their body temperature on their own, so they developed a preference for a relatively warm climate.