Early Life: The Cambrian Period Summary

A Review of Early Life: The Cambrian Period by Thom Holmes

Early Life: The Cambrian Period is a nonfiction book written by Thom Holmes and published in 2008. The book explores the Cambrian Period, an exciting time span in Earth’s history. During this time period the basis of all life originated. In his introduction Holmes sets the foundation for the book. Also, providing the readers with a general idea of the topics to be discussed. He states that Early Life: The Cambrian Period “draws from the latest research to tell the compelling story of Earth’s earliest organisms and their enormous importance to understanding other species of life that have evolved since”, giving readers a small insight to his commitment to thoroughly explain each step

Holmes introduced James Hutton to his readers. He explains Hutton’s role by describing him as a scientist “whose Plutonist theory was one of the first to explain the interior composition of Earth, originated his theories about geological processes in the observation of natural forces that could be seen in the planet’s crust” (p.45). Holmes wrote that in the same year as Hutton’s death in 1797 Sir Charles Lyell, a British naturalist, was born and it was as though he “[picked] up where Hutton left off” (Holmes, 2008, p.47). Holmes goes on to explain how Lyell embraced Hutton’s ideas and used them as motivation for his own work (Holmes, 2008, p.47). In 1830 Lyell introduced his “simple guiding principle to explain the age of Earth: The present is the key to the past” (p. 47). Before Lyell’s theory was proposed it was commonly accepted in the science community that God created Earth, all life, and that it was merely 6,000 years old. The time scale for categorizing age is broken into intervals of descending size: eons, eras, and periods. According to Holmes (2008), “From the work of early geologists came two basic guidelines for examining layers of Earth: the principles of superposition and cross-cutting” (p. 48). Readers also learn about relative dating and absolute dating. Cross-cutting is the idea that an object is younger than anything it cuts across. Relative dating is when one layer of Earth is compared to a previously identified layer. This method is only accurate if the time line is within a few million years through. Absolute dating is when the age of a fossil is narrowed down to within a few