The Greenhouse Effect and Climate Change - Climate And Human Evolution

Earth scientists are in the midst of a revolution in their understanding of how climate change occurred in the past. Researchers are discovering the geological and astronomical forces that have changed the planet's environment from hot to cold, wet to dry, and back again, over hundreds of millions of years. Dramatic climate change is nothing new for planet Earth. The climate of the past 10,000 years, during which civilization developed, is a mere blip in a much bigger history of climate change. In fact, Earth's climate will most certainly continue to go through dramatic changes—even without the influence of human activity. Most scientists believe that, if not for extreme climate shifts some 65 million years ago, most of the animals on Earth today, including humans, would probably not be here.

Astronomical cycles have caused the climate to fluctuate between long periods of cold lasting 50,000 to 80,000 years and shorter periods of warmth lasting about 10,000 years. Some scientists believe that these geologically rapid shifts between warm and cold were the catalyst behind human evolution, forcing humans to adapt physiologically and socially in order to cope with the changing climate.