Humans became the dominant species after the extinction of the dinosaurs. It is believed that there was a global event of some sort that led to their extinction. As mammals began to rise, humans became the most dominant because of our ability to adapt, learn, and adjust to our environment. We were able to survive in environments others couldn't, and therefore continued to populate the planet rather than just certain environments. As we became greater in numbers, we also evolved with new discoveries. These new discoveries led to us being able to hunt other animals more successfully and thus putting us at the top of the food chain. Once we were there, we just evolved into the humans we are today.