"For the hundreds of thousands of years of human existence when technologies were simple or non-existent, this may have had little impact on human life and the earth that sustains it. Each generation of hunters and gatherers, then plowmen and pioneers, passed on tools to the next generation to help them survive. Change from one generation to the next was slow and hardly noticeable. In those days there was little understanding of science and how things worked, and explanations were not scientific."