Physiologically we are the same. Teeth break up food, saliva is secreted of the same chemical make up, gastric juice, same, bile, same, exchange of o2 co2, same, kidney, liver filtration, same, assimilation, transport, nutrients entering cells, same, waste disposal, same. The difference we experience is due to different states, some of which may be permanent. The idea that one member of the species is by nature a carnivore and another is by nature a vegan is out of accord with physiological principles.