All animals have the same basic brain chemicals, like dopamine, serotonin, endorphin, and cortisol. Neurochemicals motivate a body to approach what feels good and avoid what feel bad. Animals don't override these impulses, so they help us understand how our brain chemicals work.
A thirsty elephant surges with dopamine when it finally drinks water, and that wires it to find water in the future. The next time the elephant is thirsty, it walks in the direction that feels good. This works because dopamine is triggered by the sights and smells of water holes past. Conscious effort is not necessary because electricity in the brain flows like water in a storm, finding the path of least resistance. Every neuron active during a dopamine experience gets linked to the well-developed dopamine pathway, so it flows easily in the future. Dopamine triggers a good feeling when an animal meets a need, and paves a pathway to release more good feelings when we see another way to meet a need. The first step of a twenty-mile trek to water is fueled by dopamine, and so is every step after that.
Humans associate dopamine with the joy of finishing a marathon, falling in love, or finding a bar that's open at 2am. These don't seem like survival needs until you remember that the mammal brain wires itself in youth when your needs are met through others. Your early dopamine surges wired your dopamine to turn on in ways that worked before. If you keep trying to stimulate your dopamine, you can end up repeating a behavior more than is good for you. This is less of a problem in the state of nature, where hunger, thirst, predation, and reproductive competition are constant threats. Dopamine relieves that sense of threat, so a brain that constantly seeks it is more likely to survive. My next post will explain how dopamine tells a monkey which leaves to eat, and why a droop in dopamine gets a monkey so upset. Our happy chemicals did not evolve for partying but to guide us toward things that met survival needs in our past. My books Meet Your Happy Chemicals, I, Mammal, and Beyond Cynical explain the ups and downs of this operating system we've inherited from earlier animals.