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The genetic paradox Neel sought to address was this: diabetes conferred a significant reproductive (and thus evolutionary) disadvantage to anyone who had it; yet the populations Neel studied had diabetes in such high frequencies that a genetic predisposition to develop diabetes seemed plausible.
However, environmental factors (almost certainly diet and weight) play a large part in the development of type 2 diabetes in addition to any genetic component. Genetic risk for type 2 diabetes changes as humans first began migrating around the world, implying a strong environmental component has affected the genetic-basis of type 2 diabetes.
Today, the term "diabetes" most commonly refers to diabetes mellitus. Diabetes mellitus is itself an umbrella term for a number of different diseases involving problems processing sugars that have been consumed (glucose metabolism). Historically, this is the "diabetes" which has been associated with sugary urine .
A large body of molecular evidence supports a variety of mechanisms for large evolutionary changes, including: genome and gene duplication, which facilitates rapid evolution by providing substantial quantities of genetic material under weak or no selective constraints; horizontal gene transfer, the process of transferring genetic material to ...
The role of genetic drift is equivocal; though strongly supported initially by Dobzhansky, it was downgraded later as results from ecological genetics were obtained. The primacy of population thinking: the genetic diversity carried in natural populations is a key factor in evolution.
Studies with monkeys show that injecting high-insulin-producing forms of these cells into the animals can “cure” type-1 diabetes for about six months. Human trials are underway.
A considerable number of studies have used genomic methods to identify specific human genes that show evidence of adaptive evolution. Table 2 gives selected examples of such genes for each gene type discussed, but provides nowhere near an exhaustive list of the human genes showing evidence of adaptive evolution.
Apples. The original source of sweetness for many of the early settlers in the United States, the sugar from an apple comes with a healthy dose of fiber.