The ultimate cause of much historical, social and cultural change is the gradual accumulation of human knowledge of the environment. Human beings use the materials in their environment to meet their needs and increased human knowledge of the environment enables human needs to be met in a more efficient manner. When human knowledge of the properties of gases and vacuums grew they were able to produce an internal combustion engine that greatly improved the human need for transport. Motor cars and aeroplanes were invented and agriculture and sea transport were improved. The human environment has a particular structure so that human knowledge of the environment is acquired in a particular order. The simplest knowledge is acquired first and more complex knowledge is acquired later. This resulted in improvements to both motor cars and air transport throughout the twentieth century so that people had much better and more affordable transport by the end of the century. The growth of world trade, tourism, international migration and globalization can partly be attributed to improved transport systems. This means human social and cultural history, has to follow a particular course, a course that is determined by the structure of the human environment.