ABSTRACT
If the genetic mechanisms controlling physical activity in humans evolved before the basic mammalian species split – for example, it is estimated that mice and humans split on the evolutionary tree approximately 62–100 million years ago – then any insights gleaned from mice as to the genetic mechanisms responsible for physical activity regulation would be potentially translatable to humans. Hypothesis that food availability would have been a selection pressure contributing to the evolution of the genetic regulation of physical activity was based on the copious literature showing an inverse relationship between physical activity and food availability. It is well established that moderate reductions in caloric intake significantly increase physical activity in several animal species, with suggestions that the same responses occur in humans. The lower intensity and longer duration of physical activity would have required the pre-technology farmers to favor fat rather than carbohydrates as a fuel source to fulfill the physical activity energy requirements of agriculture.
