The most basic aspects of humanity like how we walk and how we speak are the result of evolution. Around 6 million years ago, early hominins began to walk on two legs rather than four. The human brain evolved to become larger and more complex, allowing for sophisticated language and tool-making. The way in which humans have evolved explains how we live today. However, the general conception that evolutionary changes occur over millions of years is only sometimes true. Evolution can occur in under a decade which is known as microevolution.