Why we think
It may be a question so basic, to the point that is sounds stupid. After all, the thinking process is so abundant in humans in everyday life, so it’s considered from granted. We cannot even think of ourselves without the capability of thinking (sic); we wouldn’t exist without it, right? (cogito ergo sum). At the same time, we have to admit that humans, as the cornerstone of evolution has managed to upgrade the thinking process so much that it is now capable of juggling with extremely complex topics, such as the structure of the universe, the meaning of existence, the inner workings of the human mind, etc… This level of complexity can defocus us from the most primal purpose of the thinking process, the one that evolution favored and thus granted us with the ability to think.
In terms of Noesis Theory, I have outlined in a previous post the main mechanism that I think the brain uses, which is to utilize past experience (the past) in order to translate the incoming stimuli (the present) into the most preferable potential outcomes (the future) and try to bring this future into reality.
When you connect the mechanism of thinking with the description above, it’s very easy to link thoughts to "the future". In other words
the mechanism of thinking was given to us in order to be able to predict the future.
The act of thinking is in reality a projection of limited info we have into what could be; into a future.
So when I converse with you and mention the word apple, you will probably bring into your mind the picture of an apple, into your mouth the taste of an apple. Why? Because back the jungle, when you heard the sound of flowing water (thirsty after some hours of scavenging), via your thought process you would be able to predict a candidate future of you finding this spring and drinking its refreshing water. This would be translated as a preferable future, and you would therefore strive to make it a reality.
So we are programmed to experience one thing and immediately think what can come next, and how we can turn this into our benefit. That’s why we "were granted" thinking by… evolution. Our inner vision/smell/taste/hearing, our imagination, it’s there to envision the future.
You might argue that there are all too basic things that I’m describing. That the modern homo sapiens has a much more advanced thinking ability. I can agree with you, but I would also add that this is just (much) better pattern matching, overlaid on top of the very basic evolutionary mechanism that I described. Because the core principle of guessing the future (in order to pick the most favorable one) should be the foundation for thought. In fact, I would even guess that for the same reason all animals with a relatively complex brain have the ability to think. The main difference should be located in their ability to grasp abstract concepts and link distant patterns via the pattern matching capability of their brain. But the core principle (and evolutionary need) of thinking should remain the same across all non-simple living beings.