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The evolutionary reasons why women are colder than men

The researchers: "The phenomenon is not unique to humans. In many species of mammals and birds, the females prefer warm places, while the males prefer a cooler temperature." The researchers suggest that this is an inherent difference between the temperature sensing systems of the two species, which developed during evolution. The gap creates a spatial separation between males and females, which reduces competition and aggressiveness between couples

A woman and an air conditioner. Illustration:
A woman and an air conditioner. Illustration:

A scientific explanation for the war over the air conditioner remote: Researchers at Tel Aviv University's School of Zoology offer a new evolutionary explanation for the well-known phenomenon where women bring a sweater to work, while their male colleagues feel comfortable in a tank top in the air-conditioned space. The researchers state that the phenomenon is not unique to humans, and if we broaden our point of view, we find that in many species of birds and mammals the males prefer a cooler temperature than the females.

The researchers: "We suggest that males and females sense temperature differently. This is a built-in evolutionary difference between the heat-sensing systems of the two sexes, which is related, among other things, to the reproduction processes and the care of the offspring."

The research was conducted under the leadership of Dr. Eran Levin and Dr. Tali Maguri Cohen from the School of Zoology and the Steinhardt Museum of Nature at Tel Aviv University, Yosef Kiat from the University of Haifa and Dr. Hagi Sharon - a pain specialist from the Faculty of Medicine at Tel Aviv University and the Ichilov Hospital. The article was published in the journal Global Ecology and Biogeography.

The new study included an in-depth statistical and spatial analysis of the distribution of dozens of species of birds and bats living in Israel, alongside a comprehensive review of the international research literature on the subject. Dr. Levin, who researches among other things the physiology and behavior of bats, noticed in his previous studies that during the breeding season the males and females usually separate, with the males inhabiting cooler areas. For example, entire colonies in the caves on the slopes of Hermon consist of only males this season, while in the warmer Kinneret region there are mainly females who give birth and raise the cubs there. The phenomenon aroused his curiosity.

In addition, an extensive review of the research literature revealed that a similar phenomenon has been observed in many species of birds and mammals, and there are many examples of this: in migratory bird species, the males spend the winter in colder areas than the females (it is important to note that in birds the separation between the sexes occurs outside the breeding season, since the males participate in raising the chicks); In many mammals, even in species that live in pairs or in mixed herds all their lives - the males will prefer shade while the females warm up in the sunlight or the males will go to mountain tops while the females will stay in the valleys.

Following the literature review, the researchers conducted their own study. They sampled information collected in Israel for nearly 40 years (2018-1981) on thousands of individuals of 13 species of migratory birds from 76 sites (data from the Israeli Habitat Center and the Steinhardt Museum of Nature) and 18 species of bats from 53 sites (Data from the researchers and the Society for the Protection of Nature). In total, the study included over 11,000 individuals, from Hermon in the north to Eilat in the south.

The reason for choosing birds and bats is the fact that they fly and are therefore very mobile, and the researchers hypothesized that the spatial separation between the couples - sometimes to the extent of staying in different climate zones - would be particularly clear in these groups. Moreover, the great climatic diversity of Israel allowed them to examine individuals of the same species living in very different climatic conditions.

The research findings clearly showed that the males prefer a lower temperature than the females, and this preference creates a separation between the sexes during certain periods in the breeding cycles, when the males and females do not need, and may even interfere, with each other.

Dr. Levin: "Our research proved that the phenomenon is not unique to humans: even among many species of birds and mammals, the females prefer a warmer environment than the males, and in certain periods these preferences cause a separation between the two sexes. In light of the findings, and the fact that this is a widespread phenomenon, we hypothesized that it is a difference between the heat sensing mechanisms of females and males, which developed during evolution. This difference is essentially similar to the well-known differences between the pain sensations of the two couples, and is influenced by differences in the neural mechanisms responsible for the sensation and also by a hormonal difference between males and females.

Dr. Magori Cohen points out that the difference has several evolutionary explanations: first, the separation between males and females reduces the competition for resources in the environment, and keeps males away from the females who may be aggressive and endanger the puppies. And in addition, females of many mammals are required to protect childbirth at a stage when they are not yet able to regulate their body heat by themselves, so the preference for a relatively warm place has developed in them;

Dr. Levin and Dr. Magori Cohen conclude: "Bottom line, if we return to the world of humans, it can be said that the difference in temperature sensation is not meant to make us fight with our daughters/partners over the air conditioner, but on the contrary: it is meant to make the couple take some distance from each other sometimes, so that both parties will be more comfortable and quieter. The phenomenon can also be linked to sociological phenomena observed in many animals and even in humans, in a mixed environment of females and males: the females tend to make a lot of contact with each other, while the males are more distant and shy away from contact."

More of the topic in Hayadan:

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