Mutations Helped Humans Survive Siberian Winters

sciencehabit writes "Researchers have identified three genetic mutations that appear to have helped humans survive in the frigid climate of Siberia over the last 25,000 years. One helps the body's fat stores directly produce heat rather than producing chemical energy for muscle movements or brain functions, a process called 'nonshivering thermogenesis.' Another is involved in the contraction of smooth muscle, key to shivering and the constriction of blood vessels to avoid heat loss. And the third is implicated in the metabolism of fats, especially those in meat and dairy products—a staple of the fat-laden diets of Arctic peoples."

Comments

I can think of one trillion-dollar industry...

[dalias]

I can think of one trillion-dollar industry that might be interested in knowing how to cause 'nonshivering thermogenesis' in fat cells on demand...

Re:I can think of one trillion-dollar industry...

[Anachragnome]

"...and the weight loss industry. ;-)"

I don't see why--the adaptation allows Eskimo and Inuit (among others) to STORE fat--in large quantities--to allow for the generation of heat directly rather then through the much slower chemical process that the rest of us utilize. While you and I would sit there shivering our asses off, the Eskimo sitting next to you would simply be burning fat reserves, comfortably. I've experienced this exact situation while ice fishing--shivering makes it really hard to bait a hook without including your finger in the deal.

Most Eskimo/Inuit that I've met (I lived in Central Alaska for 10 years) were what most people would call "chubby"--they had a consistent, yet normal layer of fat that could provide them with emergency heating in the event they REALLY needed it. Falling through the ice in the middle of winter would be an example of such an emergency. Otherwise, they carry that fat around all year. Even in summer, fatty foods are a large part of the Eskimo/Inuit diet. But, I'd like to point out that I've never met a truly obese Native Alaskan--I'm guessing because they don't eat all the crap that most other Americans do--it costs too much to ship it there. While most of us would trim fat off of our meat, the fat is the important part of the catch up North. Muktuk (a common Eskimo/Inuit food) is pure whale fat--there is no meat whatsoever.

Interestingly, the Athabaskan peoples traditional range overlaps that of the Eskimo and Inuit where there are no large mountains that block travel between the interior and the coast (like the Brooks Range does). This is interesting because Athabaskan folks are built much different--they tend to be much slimmer in both bone and tissue--yet share many of the same foods and climate. They one thing missing from the Athabaskan diet is marine mammals of the large and fatty variety--whales, seals and walrus. Eskimo and Inuit eat them but the Athabaskans do not really, unless social circles overlap (more of a modern development). Both groups eat salmon, as the rivers from the coast reach far inland where the Athabaskan group historically occupied, and the interior (Athabaskan group) can actually get much colder then the North Slope of Alaska. The three characteristics discussed in this article also exist in most marine mammals.

Perhaps there is some difference to the fat in marine mammals that isn't present in the other main source of fat, namely salmon, and that consuming it led to the adaptation, rather then this being an environmental adaptation? After all, the Athabaskan peoples live in much the same environment, yet are built totally different (ie, do not have large fat reserves).

Arterial plaque?

[Anonymous Coward]

I read a theory once that I found interesting: that arterial plaque is a legacy of survival in an ice age or in an extremely cold environment like Siberia.

Here's how it goes, from memory: Humans get antioxidants from plants, but in extreme conditions plants were less available and humans may not have gotten enough antioxidants. Absent the antioxidants, free radicals posed a greater health risk.

Arterial plaque provided some defense against the deleterious effects of the free radicals, and helped the humans survive the freezing times... long enough to reproduce. Maybe in middle age the hardening of the arteries had deleterious effects of its own, but evolution is all about what helps reproduction, not so much what helps the individual live to a ripe old age.

This sounds sort of plausible but I don't have the background to evaluate it. It could also be one of those "wet streets cause rain" theories that invert cause and effect... is arterial plaque not the body's defense against free radicals but simply damage caused by them?

Re:Dairy for 25k years?

[docmordin]

Lactase persistence into adulthood is a relatively recent, as you speculated, and is thought to have been introduced approximately 10,000 years ago. For a nice overview, you can peruse:

D. M. Swallow, "Genetics of lactase persistence and lactose intolerance", Ann. Rev. Genet., 37: 197-219, 2003
E. J. Hollox, M. Poulter, M. Zvarik, V. Ferak, A. Krause, et al., "Lactase haplotype diversity in the Old World", Am. J. Hum. Genet., 68: 160-172, 2001
M. Slatkin and G. Bertorelle, "The use of intraallelic variability for testing neutrality and estimating population growth rate", Genetics, 158: 865-874, 2001
M. Slatkin, "Balancing selection at closely linked, overdominant loci in a finite population", Genetics, 154: 1367-1378, 2000
J. Metneki, A. Czeizel, S. Flatz, and G. Flatz, "A study of lactose absorption capacity in twins", Hum. Genet., 67: 296-300, 1984
G. Flatz, "Gene dosage effect on intestinal lactase activity demonstrated in vivo", Am. J. Hum. Genet., 36: 306-310, 1984
T. Sahi, "The inheritance of selective adult-type lactose malabsorption", Scand. J. Gastroentrerol., 9: 1-73, 1974
G. Flatz and H. W. Rotthauwe, "Evidence against nutritional adaption to tolerance to lactase", Humangenetik, 13" 118-125, 1971

Re:A most interesting question: What did they lose

[MarkRose]

It wouldn't surprise me if I had one or more of these mutations.

I find temperatures above 21C unpleasant. In December, I slept a couple nights in -25 temperatures in a -12 rated sleeping bag and was perfectly comfortable. I rarely wear a jacket above 0. I've taken a 45 minute casual swim in 10 water in nothing but shorts and felt a little chilled but fine (though it was sunny).

But I pay for it in the summer. Once it hits 23 my brain slows down. Around 26 it completely shuts off. I've experienced temperatures up to 40, but I'm glad those days are rare.

It's easy for me to overheat. I went on a winter hike in -15 weather and ended up getting moderate hypothermia -- because I left dressed in a "normal" amount of winter wear and sweat my clothing through. I was steaming. Thankfully I had a change of clothes, and two hours in a -7 sleeping bag got me warmed back up to normal.

People think I'm weird for enjoying -30. But I'd much rather have that than 30. I still find it odd that much of the world lives in near-constant 30 and find those high temperatures comfortable.