In this illuminating [sorry!] study, Parker contends that light is the driving force behind evolutionary change. Light, he argues, is the most prevailing environmental element. Crossing biology, geology, ecology and physics with a bridge of optics, he shows how many body structures have varied due to light's availability and intensity. Most important to the reader, is his contention that when life developed a greater sensitivity to light, evolution was given a significant boost. We call the time of that "boost" the Cambrian Explosion. According to Parker, the mechanism driving the boost was the evolution of the eye. The wide diversity exhibited by evolution's abrupt advances around 550 million years ago produced creatures whose descendants are cats, bears, birds, and you. Parker provides a wealth of background material in developing his thesis. The forces of plate tectonics, the way light is absorbed, reflected, bent, and even biologically generated are all presented. He shows the relevance of each aspect in a slowly and carefully built concept.
Parker presents his theme with verve. "Let there be images!" is a concluding example. New ideas in science tend to use a forceful approach. Since he's laid a firm Darwinian foundation for this exclamation, perhaps his enthusiasm is warranted. He explains much about early life, the nature of light and how animals have adapted body plans to use light effectively. Parker shows how new research tools can analyse fossils to reveal the past wasn't the soft, dull, colourless world often portrayed. Some of the tricks developed by Nature millions of years ago weren't duplicated by human technology until very recently. Light, he explains, was both an attractant and a repellent in the shallow seas of early oceans.
The mortar binding the facets of Parker's idea is predation. Both eaters and eaten needed to detect each other to survive. In parallel with the eye, bodies changed to avoid detection and deflect biting mouths. Survival in evolutionary terms, he reminds us, means more than eating or avoiding being a meal. Vision enhanced the process of sexual selection, with the new body forms exhibiting colours to attract mates. These and other factors combine to provide what Parker calls his "Light Switch" view of the Cambrian period. As a foundation for his hypothesis, Parker joins the ranks of Eldredge and Gould's "punk-eek" [punctuated equilibrium] cabal of evolutionary biologists. This step is taken to grant eye evolution a rapid pace in line with the many changes the Cambrian Explosion seems to evidence. That's unfortunate, since it isn't necessary and he refutes the idea many times in citing his own evidence. A species span of
120 million years without a bump is equilibrium indeed!
Parker's ebullient prose is supplemented by excellent line drawings and photographs. These provide both background and examples of his points. His style, while ardent, is a bit rambling, although this can be forgiven in a book covering so many aspects of evolution's path. What cannot be forgiven is the lack of any bibliography or notes. This lack is outrageous and insults the reader. Although many researchers are presented, few titles grace the pages, leaving the reader with the task of seeking further information or confirmation almost from scratch. The publisher has no excuse for allowing this lack. Read this book, reflect on Parker's ideas, and remember there are other proposals for the cause of the Cambrian Explosion equally or better presented.