Part 6, Chapter 27 Summary and Analysis

Biological determinism is the belief that human beings are the ultimate and intentional end product of evolution. Although Bryson dismisses it as a fallacy in previous chapters, he indulges in biological determinism in the title of this section, "The Road to Us." The implication is that humankind is the highest possible achievement of nature, instead of just one of 35 million species on earth.

The Earth's thermostat is a delicate instrument. In 1815, a volcanic eruption in Indonesia and the tsunamis that resulted killed 100,000 people. It was the largest volcanic event in 10,000 years and was 150 times as powerful as the eruption of Mt. St. Helen's. The volcano spewed 36 cubic miles of ash and dust, which diffused into the atmosphere and blocked out the sun.

The concept of ice ages was slow to gain popularity among scientists, despite...