Transportation Minister Merav Michaeli announced that she would raise the temperature on trains to suit women’s body heat, and sparked a minor storm.
That women feel colder — that is a well-known fact.
But the question that occupied me was: why is this so? What evolutionary advantage is there in women being more sensitive to cold?
I want to offer an interesting evolutionary explanation, one that, after it occurred to me, also received support from a study on bats and other mammals.
The facts are clear: women suffer more from the cold. It is plain to see and has been proven by research as well. The reasons have also been discovered, and they are related to women’s slower metabolism and lower blood pressure.
But what caused this? What evolutionary advantage led to these differences?
Since I have not seen any explanation of this phenomenon in humans, I will offer an explanation that has been rolling around in my head for several years:
Women’s temperature is calibrated to the temperature of babies. That is how they keep the babies warm and raise their chances of survival.
Here is the explanation, through a typical scene from our family life:
A freezing winter day. I want to take the little one out for a stroll in the stroller so he can breathe some fresh air. I dress him in warm pants and a shirt. Seems perfectly reasonable to me. A moment before I leave the house, Neta catches me red-handed and is horrified: that’s how you’re taking him out? He’ll freeze! And then she dresses him in a sweater, a coat, a scarf, a thermal undershirt, long johns, a wool hat and ear warmers.
Now he’s ready! she declares.
Which of us is right?
Neta.
Babies really do feel colder. But as a man who is comfortable even in winter, I cannot sense it.
Since in the era when we were hunter-gatherers it was the women who tended to be with the children, a synchronization had to develop between babies’ sensitivity to cold and women’s body temperature.
For anyone not quite sure how evolution’s natural-selection mechanism works, let’s describe it like this:
In a cave of twenty women, fifteen had no particular sensitivity to cold. They wrapped their children less well, and fewer of their children survived. Their genes passed on to fewer descendants. The children of the five women who were sensitive to cold, on the other hand, survived better, and so the cold-sensitivity genes were passed down to their daughters. After a few generations of births, the genes of the cold-sensitive women rose and spread until a good match formed between babies’ sensitivity to cold and women’s sensitivity to cold.
Further evidence for this claim comes from the fact that in women at menopause it actually flips — and they suffer from heat!
In other words, from the moment the fertile years end, this trait is no longer needed, and women’s sensitivity to cold becomes similar to men’s.
Recently, researchers at Tel Aviv University’s School of Zoology conducted a study and found a similar phenomenon in bats. In his earlier research, Dr. Eran Levin noticed that during the birthing season the males and females tend to separate, with the males occupying cooler areas. Entire colonies of mouse-tailed bats in caves on the slopes of Mount Hermon and in the Hula Valley consisted, in that season, of males only, while in the warmer Sea of Galilee region mostly females remained, giving birth and raising their pups there. The study’s 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 of the reproductive cycle, when the males and females do not need each other and may even get in each other’s way.
Another partner in the study, Dr. Magory Cohen, explained that the difference has several evolutionary explanations. First, the separation between males and females reduces competition for resources in the environment, and keeps away from the females males who may be aggressive and endanger the pups. In addition, the females of many mammals must protect their young at a stage when they are not yet able to regulate their own body temperature, and so they developed a preference for a relatively warm place.
“The bottom line,” says Dr. Magory, “is that if we return to the world of humans, we can say that the difference in how we sense temperature was not meant to make us fight with our partners over the air conditioner, but the opposite — it was meant to make partners take a little distance from each other at times, so that both sides can be more comfortable and at peace.”
So they argued that the reason is separation while raising the offspring, whereas what came to my mind was the regulation of babies’ cold. Either way, it will be interesting to keep exploring the evolutionary reason behind the battle over the air conditioner.
