Thank you for the great question.
Humans have extraordinary mental abilities that allow us to achieve everything from building skyscrapers to writing poetry. Despite our great capabilities, I would note that other species on the planet have their own amazing mental abilities that can rival our own. For example, the great feat of mathematical reasoning carried out by Tunisian desert ants.

Each day, these ants leave their nest and search the desert for food. Once they find food, they then have to solve a tough problem: finding their way back home. Scientists discovered that the ants do this with trigonometry, that is, by computing the best path home given their current location, the position of the sun in the sky (meaning they have a sense of time too), and their knowledge about where the nest is located. They usually are able to do this within 2-degrees of error, much better than I would do on a trigonometry test! Human reasoning is amazing certainly, but not without rivals from other animals, even by individual ants.

You ask a second excellent question, where did all these amazing thinking and reasoning abilities in the natural world come from? Thinking and reasoning, called cognition by scientists, takes place in the central nervous system which includes the brain. The brain, in fact, is the most complex object in the universe, and exactly how it works and develops is still a mystery for future scientists to figure out.

However, we do know something about the origin of complex natural things like the brain: that it must be a product of evolution by natural selection. That is, the genes that create brains were best able to replicate themselves because they solved problems in their environment. Different animals face different problems in their environments and their brains evolved to solve those particular problems.

Human cognition, thinking and reasoning, is no different. It is done by our brains which were designed by natural selection to solve problems that our ancestors faced, including finding food, avoiding predators, helping your relatives and friends, navigating the world, and communicating with each other. Also, many of our most amazing abilities like writing and math and culture come about as by-products of systems in the brain that were designed for other solving problems we faced over evolutionary time. We can explain extraordinary powers of human thinking by studying our evolutionary history, what problems we faced in the last million years, and how the brain evolved to solve them.

Human beings are not the only species that have minds that can think and reason!

We used to believe that we were, but that is because we have an ability to communicate via language that other animals lack. For example, remember that the word "dumb" in English originally meant unable to speak rather than stupid, but people assumed that those who could not speak were stupid because they had no way of gauging their smarts. Other animals (and many plants) do communicate, but not via language. Humans apparently have an evolutionary trait that allows us (or forces us) to learn some kind of language, which we then use to communicate concepts that are not immediately present. However, numerous experiments have now shown that many other species of animals do understand the abstract concepts that we humans once thought were unique to ourselves, but just can't communicate them as effectively as we can. These other animals include such diverse creatures as dogs, ravens, and squid.

It's hard to communicate with other intelligent species, so we don't know how smart they are. Imagine a dolphin trying to get us to make clicks to answer its questions. More and more, scientists are discovering intelligence in other animals. Koko the gorilla died recently, and she knew lots of words and communicated with them. You can read about her. When someone paints a spot on the forehead of an elephant, and the elephant looks in a mirror, it raises its trunk to touch the spot that was painted on it. I don't know how many of the elephants do that, but scientists were surprised. And a dog knows whether you're happy with it or angry at it, which takes a certain amount of understanding. But there's obviously also a huge difference between us and the other animals - just look at all the changes we've made in the world!