The St John's water dog, a common ancestor to modern dogs, exemplifies how genetic traits can evolve for specific environmental needs, such as high food motivation to aid in tasks like retrieving for fishermen. A mutation linked to this food motivation has been found in about 25% of pet Labradors and 66% in guide dogs, suggesting a possible selection for traits that enhance a dog's willingness to work for food. Although no direct correlation between the mutation and trainability has been established, the findings highlight how a single genetic change can significantly influence a dog's energy management and food intake behaviors. These genetic variations among dogs mirror similar trends in the human population, further emphasizing the impact of genetics on obesity and food-related behavior.