"During the brief time since James Watt's commercial production of the improved Newcomen steam engine in 1775, a revolution unparalleled in human history has occurred at all levels of society and has penetrated all aspects of culture. The technological innovations are, of course, dramatic, but equally important are the biological, political, social, and economic consequences of modernization. From a biological perspective, the most important consequence is the extension of the human life span and the growth in human numbers. In the past two centuries, life expectancy has nearly tripled and the population of our species has multiplied five times over."