Our cat, Eleven, is a simple creature. She likely doesn't have emotions the way that you and I think about them, but she does feel pleasure and pain. She continually seeks pleasure and avoids pain. She can feel "good" when she's purring in my lap, or sees her food being served, but she probably doesn't have a complicated emotion related to the activity. Whereas a human might feel gratitude for being fed, or love while cuddling, a cat just feels "good". Similarly, when it's feeding time and our cat is not being fed, she feels "not good". She does whatever it takes to get out of "not good" territory and into "good" territory. It's as simple as that. She meows, she attempts to open the fridge (each time thinking it will be the time she figures it out), she sniffs her food bowl–anything that might help her avoid this agony of hunger and get back to the land of the "good" where she's full and content. Her brain is receiving "bad" signals so that she does something about it. Her brain never wants to be in "bad" territory, so when it receives "bad" signals, it cues up a set of actions designed to fix the problem and steer back into the land of the "good".

Warm is good. Cold is bad. Full is good. Hungry is bad. Safety is good. Danger is bad. Our cat follows a simple set of rules that lead her to meowing for food, sitting in front of the fireplace, and laying on my keyboard. She's not "thinking" or judging or strategizing, she's just following those rules that her species has evolved over millennia.

This got me thinking, cats are just larger, cuter, furrier bacteria.

Instead of legs, bacteria use rotors and hair-like "flagella" to move through their environments. In fact, bacteria have the original motors, an irreducibly complex machinery that allows them to find nutrients:

The movement of these rotors is defined by one rule, and one rule only: Move randomly until you come upon nutrients, then stop moving until the food runs out, at which point start moving randomly again. That's it! There's no strategy or larger plan for the single celled bacteria; it simply turns its rotors randomly until it comes across a carbon source, something delicious like decomposing flesh, and then turns off the random movements while it feeds. That's how bacteria evolved to move and "find" food. For bacteria, "good" is anything that involves being on food, and "bad" is everything else. Good = don't change a thing. Bad = move around.

As the University of Wisconsin explains it:

With no brain to supply motivation, a bacterium instead must rely on chemical cues from its environment to provide an impetus to move. This process, known as chemotaxis, is completely involuntary. Bacteria simply respond to the tugs and pulls of their environment to take them to useful places. A bacterium tracking down a chemical stimulant (such as a nutrient) moves in a way known as “random walking.” About once every three seconds, a moving bacterium will suddenly “tumble,” a brief pause that allows the organism to reorient itself. If the chemical cues are right to continue, the bacterium will begin moving on the same path. If not, it will change course, creating a jagged path toward its destination.

Our cat is just bacteria that evolved legs, claws, teeth, eyes, ears, meows, cuddles, and memory as extra tools to navigate toward "good".

And maybe humans aren't so different either. Like bacteria, we all started as single celled organisms in a primordial soup billions of years ago. We share DNA and ancestors with bacteria. Our hopes, dreams, and desires are built on the same simple machinery of navigating to good and avoiding bad. But unlike bacteria, we've built on top of those "simple" motors with billions of years of complex evolution that give us consciousness, awareness, rationality and emotions. We can actively decide how to turn the motor, even though it doesn't feel like it at times; when you sense immediate danger, your billions of years of evolution don't give you a chance to react–they take control and turn the motor for you.

Other times, there's no imminent danger and our consciousness can take the driver's seat, or at least be a sort of backseat driver, and we can make more meaningful, sophisticated, strategic decisions than avoiding immediate predators and looking for our next meal. But the basic machinery is the same, from finding love to having kids to changing career paths, we're all just turning our motors in the direction that will lead to "good", and through the lens of evolution that means surviving, passing on our genes, and ensuring our offspring survive. Everything we do, from launching rockets into space to making pancakes, is an elaborate means of moving our motors to attain those basic desires.