ABSTRACT
Movement is energetically costly, yet many animals travel vast distances as part of their normal life history. From a Darwinian evolutionary perspective, this would be unexpected unless it provided some fitness advantage for survival or reproductive success. Movement is often necessary to find food, shelter, or mates. Therefore, it is generally assumed that gene frequencies have been shaped by natural selection to support varying levels of physical activity depending on the local ecological conditions. At least two components are necessary for an individual to perform a voluntary behavior of any kind: they must be physically capable of performing the behavior and they must be motivated to do it. Both processes involve biological traits that are moldable by evolution and which, in part, shape genetic variation in physical activity levels. Physical constraints such as aerobic capacity (the maximal amount of oxygen an organism can consume during maximal physical exertion), muscle mass or composition, bone symmetry, and many others limit the ability of animals to move quickly or travel long distances (30). Hence, if ecological conditions demand that the animal displays challenging physical acts at the limit of their physical capability to survive and reproduce, then that will lead to the evolution of increased capacity for these exercise physiological features, to the extent that they are heritable.
