Take heart: Deep cold good for genes
If your ancestors survived winter, you're better off for it
Harsh migration from Africa to Europe favoured hardiest
PETER CALAMAI
SCIENCE REPORTER
OTTAWA—Here's some small comfort from science during the current deep freeze: Enduring cold weather is good for your health.
Unfortunately, the scientists aren't talking about our current suffering from icy cheeks and tingling fingers. But if your ancient ancestors put up with similar frigid conditions you're now genetically hardwired to be less prone to diabetes, heart attacks, dementia and organ failures.
"Which means you'll live longer," says Doug Wallace, a top U.S. genetics expert and lead author of the cold-is-good study.
Wallace and colleagues concluded that harsh winter climates favoured certain human genetic mutations after close scrutiny of special kinds of DNA sequences in 1,125 people from around the world.
By isolating differences in the DNA, the researchers were able to pinpoint the specific genetic sequences that allowed some people migrating from Africa 65,000 years ago to survive the much colder climate in northern Europe and Asia.
"It's the efficiency of their energy metabolism. The people from Africa who didn't have the right genetic sequences simply froze to death," said Wallace, who heads a genetics centre at the University of California in Irvine.
Those same inherited genetic sequences also mean the modern descendents of the cold-adapted migrants aren't hit as hard or as early by Alzheimer's and common age-related afflictions, the researchers say in their report published recently in Science, a leading U.S. research journal.
As well, this natural selection may explain why people respond differently to popular high-protein diets, Wallace suggests.
The findings are controversial because researchers looked at DNA within mitochondria, tiny bacteria-like structures that live inside the cells of the human body. Medical researchers have largely ignored mitochondrial DNA because it contains only 13 genes compared with the roughly 24,000 genes of the DNA in the nucleus of human cells.
Yet the mitochondria are important. They are the cell's power plant, burning oxygen, fat and sugars to produce heat and ATP, the chemical that provides the fuel for cells to perform their millions of different tasks inside the body, ranging from flexing frozen fingers to thinking about warm sunny beaches.
In people whose ancient ancestors had to survive severe cold, the mitochondria power plants burn most efficiently, producing large amounts of heat, as well as chemical energy. In warm-climate descendants who didn't need as much body heat, the under-used mitochondria spew out a form of toxic smoke, called oxygen radicals, that damage cells and accelerate age-related diseases.
"Because mitochondria are inherited solely from the mother you never have any crossovers from the other parent. The only way the mitochondria DNA can change is through mutation, which makes it possible to construct these family trees so far back," Wallace explained at a research seminar this summer.
The publication of the findings in a leading research journal like Science is a breakthrough for Wallace's mitochondria work.
"We need to start looking at genetic factors that determine the metabolic balance in the body. We need to optimize people's lifestyles to their metabolic balance," Wallace said.
The researcher said there was no special way his findings could help warm Canadians now enduring a prolonged deep freeze.
"You guys just need to move here," he said from his home in California.
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