Human evolution began in Africa six million years ago, describing the process our ancestors went through to eventually become the modern humans we are today. Major changes in the evolution of humans led to the appearance and development of modern Homo sapiens. These major changes included the shape of the skull, the size of the brain, and the size of the snout. This research paper will outline and evaluate these changes to describe and explain how modern humans evolved. Natural selection plays an important role in the development of humans over time. Natural selection is Darwin's most famous theory; states that evolutionary change occurs through the production of variation in each generation and the differential survival of individuals with different combinations of these variable traits (Natural Selection, 2009). Brain SizeEnvironmental conditions have stimulated important developments in how we became what we are today. The development of early humans faced environmental changes and developed larger bodies, larger and more complex brains. Having a larger, more complex brain was an advantage. Processing and storing much information became easier, giving early humans the advantage of interacting more socially and gaining awareness through encounters in unfamiliar habitats (Bigger Brains: Complex Brains for a Complex World, 2015 ). From two million to 800,000 years ago, brain and body size increased dramatically during a period of climate change. During this time, having a large, complex brain gave humans the advantage to interact with each other and their surroundings in different ways. Homo erectus is the oldest known human to have possessed body proportions similar to modern humans. The average brain size of Homo erectus is estimated... in the middle of the paper... which is why the mutation is observed in every human on this planet. When the jaw muscles weakened, they allowed the muscles in the head to become larger, this made room in the skull for a larger brain. The image shown on the right shows that the chimpanzee skull is much smaller because it has a larger jaw to support, the human skull is larger because the jaw is smaller. It gave the skull extra space for the front of the brain to grow. The prefrontal cortex (the largest part of the brain) gave humans an advantage, made them more intelligent. Giving them the opportunity to learn to talk about and plan for the future. The extraordinary development of our ancestors led us to become the modern, complex humans we are today. Our species' ability to create new realities in our minds that allow us to perceive things that past primates were never able to.