Sunday, October 23, 2011
I thought the Myles article for this week was so interesting. If something even as ostensibly disadvantageous as obesity was specifically selected for by nature, it emphasizes the enormous role natural selection plays in who we (and all species) are today. Here is a study with rodents, which takes an opposite approach to the study of the origins of the obesity and the potential fitness the genes confer. They took rats, some genetically predisposed to obesity, and subjected them to strenuous exercise and starvation. All the rats under study lost weight, but the effects were much less severe and extreme in the rats with the obese genes, who also survived longer thus proving potential benefits of obese genes. In addition, they also found external influences had an effect on the expression of the obesity genes, particularly in homeostasis: rats that were exposed several times to the harsh, low-food, high-stress situations had a higher rate of survival, but tended to gain much more weight once normal conditions were regained. (Which explains the predicament of yo-yo dieters...) This study confirms the theory that obese genes were originally selected for to help individuals survive less abundant lifestyles than we are accustomed to today. Thus these genes, which are so valuable in environments with food instability, makes individuals in modern society far less fit, underscoring the fact that adaptation (and evolution) always has unfinished business.