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Ever argue over the “correct” temperature for the house?

Next time, you can use evolution to back you up. 

Scientists have discovered female members of species are naturally drawn to warmer temperatures because of a built-in ‘evolutionary difference.’ Researchers in Israel studied 13 species of birds and 18 bat species to determine if the animals displayed geographical separation between the sexes. The research was published in the journal Global Ecology and Biography journal.

Turns out, they do!

The researchers at Tel Aviv University found that the males preferred lower temperatures than females, leading to physical distance between them at certain times of the year.

Research has previously suggested that the sexes experience temperature differently in humans, with women feeling the cold more because of variations in metabolism and the production of body heat.

Metabolism is a factor because it dictates how quickly heat energy is produced. On average, women have a lower metabolic rate than men.

Higher muscle mass leads to higher resting metabolism, which is linked to burning more calories and increased blood flow, both of which help keep a person’s arms and legs warm.

Men and women have roughly the same core body temperature, at over 98°F. Some studies have found it slightly higher in women. 

Regardless of this, however, our perception of temperature depends more on skin temperature. It tends to be lower for women.

One study estimated that the average temperature of women’s hands when exposed to the cold was almost 5.4°F (3°C) lower than in men.

Previous research has revealed that women often feel colder around ovulation when estrogen levels are high because it slightly thickens the blood, reducing the flow to the capillaries that supply the tips of fingers and toes, especially when it’s cold. 

In this most recent study, Dr. Levin, co-author, says, ‘We have hypothesized that what we are dealing with is a difference between the females’ and males’ heat-sensing mechanisms, which developed throughout evolution.” 

In his previous research, Dr. Levin found that males and females tend to separate during the breeding season, with the males inhabiting cooler areas. In addition, among many mammals, even in species that live in pairs or mixed groups, males tend to prefer shade, whereas females prefer sunlight. The study included around 11,000 birds and bats using data collected over 40 years.

Researchers chose those species because they fly and are highly mobile. For this reason, researchers believed spatial separation between the sexes – even extending to different climatic zones – would be evident in such groups.  

Israel’s substantial climate diversity also allowed them to study individual animals of the same species that live in very different climatic conditions. 

They found that males prefer a lower temperature than females which led to a separation between the sexes at specific periods during the breeding cycles, when the males and females don’t need, and may even interfere, with each other.

Dr. Levin said of his astounding findings, “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. This difference is similar in its essence to the known differences between the pain sensations experienced by the two sexes, and is impacted by differences in the neural mechanisms responsible for the sensation and also by hormonal differences between males and females.”

Researchers concluded that “the bottom line is, going back to the human realm, we can say that this difference in thermal sensation did not come about so that we could argue with our partners over the air conditioning, but rather the opposite: it is meant to make the couple take some distance from each other so that each individual can enjoy some peace and quiet.”

They say that 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: females tend to have much more physical contact between themselves, whereas males maintain more distance and shy away from contact with each other.”

No matter how you look at it, females everywhere tend to be colder than their male counterparts. 

You would be wise to turn up the thermostat and avoid the argument.