The Theme of Evolution in Animal Systems
We'd like to think that it's pretty common knowledge that our human minds are much different from that of a jellyfish (who has no brain) or a chameleon (whose brain has the power to make skin change colors). Humans instead have complex thought processes, memories, and language, which are a lot more practical. It's no fault of the chameleon that he can't do these things—his brain just isn't wired for it. But we'd like to see you try to turn orange without a serious spray-tan.
We can blame evolution for our inability to change the color of our skin to fit into our surroundings. Truth be told, we don't need that mode of defense. Chameleons do.
We all start out with the most primitive reptilian brain that takes care of just the basics—all they care about is stayin' alive. Between the brain stem and a cerebellum (which means "little brain"), the reptilian brain controls heart rate and balance. It directs digestion and reproduction. Because primitive animals were usually out exposed to the elements, hot and cold, their brain also manages and regulates body temperature. It does what the animal needs for survival, but not much more: it's reliable, but functionally rigid. Think of the reptilian brain like an old pickup truck with 200,000 miles on it. It may not have heated seats or Bluetooth, but it can get you from Point A to Point B.
The first mammals to come along the evolutionary tree added the limbic brain. This more advanced brain add-on includes a hippocampus, an amygdala, and a hypothalamus on top of the reptilian brain.
These brain areas allow mammals to do slightly more complex mental exercises: make memories, find experiences agreeable or disagreeable, and have emotion. These brain functions are critical to mammals' survival since they have to look for food and remember how to get back to their family. Their survival is also based on emotions; they won't seek out situations where they once were scared or frightened but seek those that made them feel all warm and cozy. Every now and then there's an oddball that prefers A Nightmare on Elm Street to My Little Pony, but we doubt he'll last too long in the wild.
The limbic brain also gives animals the ability to feel emotion towards each other, and is responsible for feelings of attachment and the need to bond. Emotions are very helpful in survival, because it provides a key motivation to finding companionship and reproducing. In essence, this brain allows mammals the ability to make those unconscious value judgments that have a huge impact on behavior.
The primate brain is the last stop in our tour of brain evolution. Here, a cerebral cortex wraps around the limbic brain, and makes up the majority of what we recognize as a human brain. The cortex gives us our imagination, the ability to use language and writing to communicate, and conscious control over emotion, activities, and thought. It allows us, and other mammals, to plan ahead for the future (whether that means leaving a few kernels of kibble left in the bowl or investing in an IRA). The primate brain is loads more flexible than the reptilian brain and is what makes us independently thinking creatures. We don't just constantly respond to outside stimuli.
The evolution of our brains is impressive, from being tiny blobs that made sure we remember to breathe to more massive organs that allow us to love, remember, and speak. What will the next brain be able to do? Time travel, probably.