When I came to Washington, D.C., for college, I bought my first winter coat. I also seriously considered transferring to a school back home. It turns out that while Texas’s endless sunny days might have played a role, there are other reasons underpinning my winter hatred. Research suggests that there are two kinds of people who tolerate the cold very well: indigenous Arctic groups, and men. And the more people are exposed to cold temperatures, the better they acclimate.
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Over the course of centuries, people who live in polar climates have evolved to be slightly more stout and to have shorter limbs, so they have less surface area, compared with their body mass, from which to lose heat. (Given my elk-like appendages, I assume that whatever shtetl my Russian ancestors hailed from was not quite polar enough.) Other studies suggest that polar peoples also tend to have more “brown fat,” which generates heat.
For several years, American anthropologists have been collaborating with Russian scientists to measure the basal metabolic rates, or BMRs, of the Yakut people of the Sakha Republic of Siberia. In Yakutsk, the Sakha’s capital city, winter temperatures hover around -30 degrees Fahrenheit. The basal metabolic rate is how much energy your body burns just to keep you alive, and a higher one reflects greater heat production. The scientists have found that Siberians have higher BMRs than people who live at lower latitudes, and that translates to them both needing more calories to stay alive and feeling warmer when it’s cold out. The Siberians’ BMRs rev up even higher as the temperature drops. According to one of the lead researchers on these studies, the Northwestern University anthropology professor William Leonard, this effect is consistent across other cold-climate populations.
Being a non-Siberian Russian can’t help me in this department. When Leonard and his colleagues compared the indigenous Siberians with nonindigenous Russians who just happened to live in the area, the Russians still had higher than average metabolic rates, but the indigenous Siberians’ rates were even higher. “With long-term, repeated exposure to cold, all humans have some capacity to increase their acclimatization to cold,” Leonard says. “But those populations with a deep evolutionary history seem to have genetic adaptation.”
The way the Siberians’ bodies generate these high metabolisms is by increasing their uptake of thyroid hormones, the chemicals released by a gland that sits in the neck. However, people who don’t have this adaptation shouldn’t just take synthetic thyroid hormones to try to replicate the effect, Leonard says. Doing so might confuse your thyroid so that it no longer functions normally. Indeed, Leonard says that there are a lot of thyroid problems among the elderly Yakut, suggesting that not even this natural cold-weather adaptation is consequence-free.