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Modern Diseases Caused by Ancient Genes

Humans have always migrated whenever and whenever we could. When early humans left Africa, they developed special genes that allowed them to survive the colder climates of Europe, Asia and North America, and these genes may be the cause of today's health problems, like obesity and aging diseases. The good news: science may have finally found a cure for Alzheimer's.

Douglas C. Wallace, at the University of California at Irvine, says that mitochondrial DNA (mtDNA), which is inherited from our mothers, changed to produce more body heat. He says, "In the warm tropical and subtropical environments of Africa it was most optimal for more of the dietary calories to be allocated to?work and less to heat, thus permitting individuals to run longer, faster and to function better in hot climates. In Eurasia and Siberia, however, such an allocation would have resulted in more people being killed by the cold of winter. The mtDNA mutations made it possible for individuals to survive the winter, reproduce and colonize the higher latitudes. This explains the striking correlation between mtDNA lineage and geographic location that we still see today in indigenous populations around the world."

But these genetic changes make it tough for modern humans. Wallace says, "When heat and cold are managed by technology, not metabolism, and people from warmer climates are eating the high fat and calorie diets of northern climates, there is a rise in obesity and the age-related degenerative diseases. The caloric intake and local climate of many individuals are out of balance with their genetic history. Thus, our genetic history is linked to our current diseases, resulting in the new field of evolutionary medicine."

When mitochondria burn food as fuel, oxygen radicals are formed. These "free radicals" have been linked to cancer and Alzheimer's. Wallace says, "Since the mutated DNA of cold-adapted people allocates more calories to heat, there are fewer left over to generate oxygen radicals. Hence these people are less prone to aging and age-related degenerative diseases."

When enough oxygen radicals accumulate, they "pollute" the body and cause cells to die. Since many of our body tissues have a finite number of cells, when enough of these die, we get symptoms of aging, such as diabetes, memory loss, deafness and vision loss, and cardiovascular disease.

But if all the calories we eat are used to produce carbon dioxide, water and energy, there's little left over to produce oxygen radicals. This is why the Inuit can eat an incredibly high fat diet and still stay healthy. However, if we eat more calories than we need to make energy, these extra calories are stored as fat. Fat leads to a large increase in free radical production, which is why obesity has been linked to some forms of cancer.

But at least there's good news about one of these diseases: Scientists may have found a cure for Alzheimer's. They?ve discovered that it causes clumps of amyloid beta (A

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