If I am eating dinner, and I want to add salt to the meal, then I try to reach the salt container, using my shoulder and arm and hand, and using my muscles and tendons and nervous system. How much of my body is involved in bringing food to my mouth? You can define this in slightly different ways, but you end up with the same result: some parts of my body allow me to bring food to my mouth. In those moments, it is entirely appropriate to say that the system is trying to bring food to my mouth. And yes, that increases my chances of having children. It is possible that something else, unknown to me, is also happening, emergent, and in 2 million years that emergent quality will be more obvious. But in the short term, it is altogether reasonable to say that parts of my body were working as a system to bring food to my mouth.