"We thought an organ like a gallbladder would have a pure genetic origin as probably most people do. Just as a short anatomical review, a gallbladder is a thin-walled sac in the duct between the liver and the small intestine, and it regulates the flow of bile to the small intestine and helps in the digestion particularly of fat in the small intestine.
The ptarmigan and other species of grouse don't have them. Presumably, their diets are so low in fat that the gallbladder is unnecessary, but some years ago we found gallbladders in captive ptarmigan that we raised from eggs at the University of Alaska, and we couldn't figure out why that would be. Eventually we tracked it down and attributed it to our inadvertently feeding the chicks a diet that was considerably higher in fat than they would get in the wild. This we believe is a classic example of a very important phenomenon called epigenetics, which literally means "beyond genetics."
Traditional genetics deals primarily with the absence or presence of genes, whereas epigenetics deals with the action or inaction of genes that are there, and the effect of the environment in turning genes on or off. So, in the case of the ptarmigan, they likely had genes for gallbladders, but they weren't operating - they weren't turned on - but when the birds received a high fat diet, it essentially turned on the gene. So this is an example of feedback from the environment - the environment affecting genes. This is becoming a major field in biology. It can be a whole revolution in our understanding of biology and it has huge potential and significance in many ways, including in human medicine."
- John Theberge, co-author of "The Ptarmigan's Dilemma: An Exploration Into How Life Organizes And Supports Itself"
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