This is the issue and it doesn't make sense that genetic makeup alone can be the sole contributing factor, as it takes many, many generations for genes to mutate. However, recent epigenetic studies indicate that genes can be altered (expressed or not) at the cellular level due to environmental changes influencing that expression. Environment in this case includes dietary consumption. When our diets became distorted at the recommendation of the "experts" starting in the late 70s, we witnessed the power of epigenetics and the influence on physical and metabolic health due to the toxic environment of so many people following a SAD approach. Genes cannot mutate fast enough to be the cause of this, but epigenetics influencing the expression (or not) of genes at the cellular level can and the influences are carried on to offspring in future generations. I'm ascribing the "drifty gene" hypothesis to epigenetics. It's of value to term it this way, as we can all learn to reverse this dynamic by changing our dietary environment. And no, we learn nothing from mouse studies, particularly those studies where the controls and eating environment are of questionable rigor and specificity.