So, from an evolutionary perspective, it makes sense that our bodies have these internal mechanisms that propel us to act in ways necessary for survival and reproduction. Let’s take hunger and thirst, for example. So these needs propel us to act in ways toward, to look for food and water. And if we’re successful, we survive, we reproduce, we pass on our genes. Now we also have a need to reproduce. Now as individuals we don’t actually need to reproduce in order to survive. Although, of course, as a species we do. it’s a little more complicated, so we’ll talk more about sex and reproduction later on in the lesson.