The Thrifty Gene Hypothesis: Why It Doesn't Work
This will be the journey into a future field that I hope some day exists, ‘obeseology’, and it will endeavor to challenge the human race to find some conclusive way to battle the elusive and ever present enemy of obesity without requiring surgical or drug intervention. By evolving the human animal in a different direction, away from the now unneeded thrifty gene hypothesis way of manifesting itself through .
13/10/2010 · The Thrifty Gene Hypothesis
Studies of different human populations indicate that human evolution continued not only after we branched off from apes, but even long after Paleolithic times. Some studies suggest that people whose ancestors came from warm, lowland environments, who had to work hard for all their meals even after food became abundant elsewhere, tend to have slow metabolisms, and people whose ancestors came from cold, highland environments tend to have high metabolisms. While one group had to survive long periods of famine, the other group likely had to metabolize lots of animal fat. What both groups have in common are lifestyle diseases in response to a modern Western diet and sedentary mode of living. There is some debate about whether gene variants leading to type 2 diabetes really resulted from periods of food scarcity ("thrifty gene hypothesis") or whether they just resulted from genetic drift ("drifty gene hypothesis").
Biologists and paleontologists have made a convincing case that life diversified tremendously during the Cambrian, and that the body plans apparent half a billion years ago showed significant similarities to body plans still thriving today. Figuring out why, and why then, is more challenging. Possible triggers include environmental changes, such as the retreat of the glaciers of Snowball (or Slushball) Earth, or the increased availability of oxygen, though those big changes happened before the Ediacaran Period. The development of predation might have spurred an evolutionary arms race, though that becomes a chicken-and-egg question of timing. Another possibility involves changes in developmental genes. Although evolution is not random, it can be driven by random changes in genes, and changes in Hox genes responsible for regulating overall body plans could have contributed to a rapid diversification of animal phyla over a short span of geologic time. Genetic changes might also have limited the diversification of phyla after that time. Evolution certainly continues today, but it doesn't appear to operate at the phylum level in the animal kingdom.
Drifty gene hypothesis | Wiki | Everipedia
The thrifty phenotype hypothesis arose from challenges posed tothe thrifty gene hypothesis. The thrifty phenotype hypothesistheorizes that instead of the "thrifty factors" arising fromgenetic factors, that instead it is a direct result of theenvironment within the womb during development. The development ofinsulin resistance is theorized to be directly related to the body"predicting" a life of starvation for the developing fetus.
The thrifty gene theory - SlideShare
A suggested different approach to the problem is the suggestionthat rather than selection favouring a few genes that are"thrifty", we possess a genome that is by default "thrifty"selected primarily due to epigenetic events. This is a combinationof the thrifty phenotype and thrifty genotype hypotheses called the"thrifty epigenomic hypothesis". The basic idea is that there hasnever been an opportunity in history to develop "unthrifty" genesbecause of the extreme pressure to select for those genes thatpromote fitness and survival through energy budgets. This ideatherefore suffers from essentially the same problems as theoriginal thrifty gene hypothesis because the evidence that suchextreme pressure exists is very weak.
The thrifty gene hypothesis Stephen Magness
The central premise of the thrifty gene hypothesis - thatfamines were common and severe enough to select for thrifty geneshas been recently challenged. Manyof the populations that later developed high rates of obesity anddiabetes appeared to have no discernible history of famine orstarvation (for example, Pacific Islanders whose"tropical-equatorial islands had luxuriant vegetation all yearround and were surrounded by lukewarm waters full of fish.").Moreover, one of the most significant problems for the 'thriftygene' idea is that it predicts that modern hunter gatherers shouldget fat in the periods between famines. Yet data on the of hunter-gatherer and subsistence agriculturalists clearly showthat between famines they do not deposit large fat stores .
Thrifty Gene Hypothesis: Challenges
This refinement is actually just a return by Neel to thealternative hypothesis to which he had alluded twenty years earlier- that modern, very-high levels of obesity and diabetes amongformerly native populations were a relatively recent phenomenonmost likely caused by changes in diet. Given that some "thriftygene" populations (like the Inuit) experienced a rise in obesityand diabetes in conjunction with a reduction of theproportion of and in their diets, Neelsurmised that the dietary causes of obesity and diabetes lay in consumption, "specifically the use of highly refinedcarbohydrate."