However, the type and evolution of the particular nature of the climate change experienced by the earth seems clearly due to the impact of human existence. Ruddiman takes a roughly chronological approach, and slowly takes the reader through the history of climatic shifts -- before humans became tillers of the land and afterwards. Major milestones in human history correspond with major anomalies in the earth's climate and atmospheric levels of important gases. Changes in Earth's orbit occur at regular and predictable cycles every ten thousand years or so and roughly correspond to Earth's major shifts in climates, either in the direction of ice ages or tropical phases. Noting the anomalous, recent increases of carbon dioxide...

To those who would merely shake their heads and say 'oh, the earth has always had climatic shifts,' Ruddiman would respond that the peculiar and particular nature of the atmospheric levels of the most recent climate shifts, since the development of agriculture, are what should concern us (Ruddiman 12). Cutting and burning of forests for pasture 8, 000 years ago caused a spike in carbon dioxide, when such levels should be going down -- a similar trend emerged regarding methane with the wide-spread domestication of cattle 5,000 years ago.
Global warming deniers will likely dispute Ruddiman's estimations of emissions so far back in human history. However, his contentions give rise to another important question, even for believers in global warming -- if sustaining ourselves, even through the most basic kinds of agriculture has had such a seismic impact upon the planet, what is a feasible way for human beings to live in harmony with the…