Has Nature really beaten Nuture in the battle of the bulge, as this Times Article, Genes not poor diet blamed for most cases of childhood obesity reveals? The article makes a glossing mention of environmental factors also playing a role in obesity, but overall the article emphasizes how genes are the major constant among obese children.
Where did those genes come from? They didn’t just magically appear right before the obesity epidemic came on the scene, evolution doesn’t work that way. These genes have always been with us, which also doesn’t make sense, because obesity shortens lifespans, meaning the genes would have been selected out generations ago. The Times article knows the answer, but doesn’t give it the time it deserves so their readers can make informed personal and political choices.
Genetically, overweight people are famine survival machines. Their ancestors were better at storing energy in fat and slowing down their metabolisms than today’s skinny people. The problem for overweight people is that the environment their ancestors evolved in, where food would regularly become scarce for extended periods of time, has been replaced with our modern world of convenience, where high-energy, easily-processed foods are in abundance all around us, commonly termed the obesogenic environment. Their body’s’ fat cells–their famine-insurance–are being over-saturated. If civilization were to collapse tomorrow, and we were all reduced to foraging for roots and berries in a post-apocalyptic wasteland, today’s fat people would rule the Earth.
In fact, this sort of culturally induced diet change is nothing new. Just a few thousand years ago, humans evolved lactose tolerance in response to our change from a hunter-gatherer lifestyle to an agricultural one.
People didn’t start drinking milk to survive in ancient times any more than people today drink soda for nutrition. It takes 15-17 pounds of grain to grow one pound of meat, cattle are a luxury item, not a necessity. Milk was yummy and an agricultural abundance that allowed humans to spend mass quantities of grain on raising livestock had made it readily available. We changed our own environment, and introduced a previously foreign animal byproduct to our diet.
Lactose Tolerance was established on the many lactose intolerant souls who died and were therefore prevented from passing on their lactose intolerant genes. The lactose tolerant members of the species survived milk-drinking long enough to have children, of whom those who were the most lactose tolerant were more likely to survive to pass on better and better versions of this adaptation to drinking the product of another species mammary glands (Yuck).
Soda tastes pretty good, but shortens our lifespans. Over a few hundred or thousand years we will probably adapt to drinking so much sugar, but it will be at the expense of millions of people who will die of diabetes, heart attacks, bad knees, etc, etc. To rationalize our obesity epidemic as genetically predetermined and something we will eventually evolve out of is an unacceptable and inhuman position to take.
So environment is still the key factor in determining obesity, just not in the parental-nurturing sort of sense. Instead we have a culturally influenced environment providing sedentary lifestyle filled with unnecessarily energy-dense foods. We can blame Nature for the genes natural selection gave us thousands of years ago, but the Nurture influence of our Global Village deserves much more blame for consciously engineering a lifestyle and diet to which our genes have not adapted.
So while a cultural shift forced humans to digest milk and is forcing us to adapt to an over abundance of simple sugars, the difference between these two situations is that we have the cognitive foresight to understand the health-hazards of obesity and reason our way into fighting it. Our big brains have unintentionally created this obesogenic environment, and these same brains have the power to engineer our way out of it.
Darwin Day
