It just occurred to me.... gastric bypass surgeries have the potential to eliminate millions from the gene pool very quickly For those that lack the self-control to stay thin when faced with virtually limited food supplies (e.g., life in an industrialized country), they can mutilate their digestive tracts in order to achieve a normal weight. The most popular surgery being the "roux en-Y" gastric bypass, which is an irreversible procedure where basically 80 percent of the stomach and a large section of the intestinal tract are essentially removed.  The surgery is very effective and can allow those that have it to quickly drop significant amounts of weight and achieve a normal BMI. However, it occurred to me that the whole point of the evolution of our digestive system and metabolism, as humans, is that we've evolved to survive famines. That's why we have large stomachs, why we are attuned to love fat, sugar, and salt (palatable foods) and why we have the ability to get fat. When food supplies are scarce, we are able to stuff ourselves quickly and store away the reserves for use later. So, if a global event occurred (say, the collapse of the US currency, or a global pandemic, or some other mass event occurred) and food supplies suddenly became scarce in the industrialized world - some of the first people to die would be those who have had gastric bypass or similar procedures to their stomachs. They would be unable to store energy supplies in their bodies for later use. They would be unable to add fat layers (which, in an environment where food is scarce, is actually adaptive). They would be the first to die off. Just a thought I had.