Is Homo sapiens Just Another Stochastic Event in the History of Life on Earth
Cairns, John Jr.
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Surprisingly, mass extinctions probably account for the disappearance of less than 5% of all extinct species _ 95% of species extinctions occur between mass extinctions. In short, extinction can occur at any time in Earth s history. The concept of sustainable use of the planet assumes that humans can live on the planet indefinitely _ or at least until the sun dies. However, human production of greenhouse gases is resulting in rapid climate change that threatens human society globally. In addition, greenhouse gas emissions are increasing markedly, and no agreement has been reached on specific goals for reducing emissions. Finally, coal is being used to replace diminishing supplies of petroleum, despite evidence that coal produces about twice as many greenhouse gas emissions per unit of energy produced than petroleum. Although alternative sources of energy (e.g., wind, solar, geothermal) are becoming increasingly popular, humankind s primary source of energy is fossil fuels. Global climate change resulting from anthropogenic greenhouse gas emissions has already affected food production, water supplies, natural habitat, and human security. Climate change and other types of habitat destruction threaten the biospheric life support system upon which human survival depends. All these issues suggest that Homo sapiens may be just another stochastic event that is adversely affecting life on Earth.