May 23, 2013
Life’s Creative Recipe
Posted on Jul 17, 2012
By Deniz Erezyilmaz
“Cells to Civilizations: The Principles of Change That Shape Life”
Is there a “grand unified theory” in biology? Developmental biologist Enrico Coen argues in “Cells to Civilizations: The Principles of Change That Shape Life” that just seven principles underlie the process of embryogenesis (how the embryo is formed), evolution, cognition and human culture. Coen’s book is ambitious and stimulating. Only time will tell whether his ideas will influence the way biologists think. In the meantime, “Cells to Civilizations” is good material for conversation and a worthwhile read.
Coen could be called a Renaissance man. He is a botanist, a developmental biologist and a geneticist. As an undergraduate, Coen waffled between chemistry and genetics, finally deciding upon genetics because the classes met later in the morning and provided coffee. Most famously, he showed that flowers are organized by three classes of genes into four circular patterns. His work has more recently focused on the evolution of leaf shape. He uses such diverse tools as genetics, molecular biology, 3-D imaging, multidimensional analysis and computer modeling of growth. It makes sense that a multidisciplinary biologist would seek to unite fields that were previously isolated from one another.
In “Cells to Civilizations,” Coen contends that seven principles, or “ingredients”—population variation, persistence, reinforcement, competition, cooperation, combinatorial richness and recurrence—“and the way they work together define ‘life’s creative recipe.’ ”
Cells to Civilizations: The Principles of Change That Shape Life
By Enrico Coen
Princeton University Press, 322 pages
The principle of combinatorial richness, for instance, appears in the genetic makeup of evolving populations, among the cocktails of regulatory proteins that pattern an embryo, in the wiring patterns of nerve cells within the brain, in the combinations of letters upon a page, and in the unique encounters between individuals in 15th century Florence, Italy, that contributed to the Renaissance.
Coen maintains that this worldview is essential in grasping the underlying mechanisms of biology, just as one must recognize that the principle governing the transformation of ice to water is the same one governing the transformation of water to vapor. “They are different manifestations of the same underlying process. This unifying perspective gives us a deeper understanding of what is happening than what we perceive by simply viewing each transition in isolation.” Through this principle we learn that the amount of energy experienced by water molecules determines their freedom of motion. Similarly, appreciating that the transformations that occur during embryonic development, evolution, in learning and in human culture arise through “common elements behind different living transformations can help us to understand the essence of each process, while also giving us a broader overview of events.” On the other hand, Coen warns against pushing comparisons too far. The principles are the same but the particulars are very different. The game of chess is an abstraction for war, he explains, but the squares in chess should not be used to plan a battle. Coen also discusses the controversial concept of memes—an attempt “to link culture and related biological processes more precisely.”
One feature that arises repeatedly in Coen’s account of biological transformations is the double feedback loop. In a double feedback loop, both positive and negative inputs regulate the level of a product, such as reproductive success, connections between two nerve cells or human achievement. In the case of reproductive success during natural selection, the success of some genes will promote expansion in future generations. This is the principle of reinforcement at work, and in this case it drives positive feedback. The unchecked success of these genes, however, will soon encounter environmental limitations. The principle of competition, at this point, creates negative feedback. Cooperation promotes further success in human achievement, while competition checks it.
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