Kostas Kampourakis - Turning Points: How Critical Events Have Driven Human Evolution, Life, and Development

Have you ever asked yourself why we have hearts? Most people would reply: In order to pump blood. Many human characteristics seem to serve goals, and these goals look quite obvious in many cases. Why do we have legs? In order to stand up and walk is an answer that would make sense to most people. Why do we have opposable thumbs? In order to grasp and handle objects, most people would also reply. And this can go on for any of our body parts and organs you can think of: brain, stomach, lungs, liver, to name a few. The roles of other characteristics may seem less obvious, but they also seem to be there. Why do we have eyebrows? In order to prevent sweat from entering our eyes is a plausible answer. Why do we have hair on our heads? In order to keep our brain warm is again a plausible answer. But if you think harder, it is not easy to assign goals to all characteristics. Why do we have toes? Why do men have nipples and facial hair? And so on. Perhaps there is a less obvious role in these cases, but it must be there, you may think. Otherwise, if they do not do anything, why would we have certain characteristics? In other words, why would characteristics that serve no use or purpose exist at all? You may have thought about questions like these in the past, and you may have arrived at certain answers like those above. In this chapter I invite you to forget for a moment your earlier conclusions and follow me on a foray into thinking about purpose and design in nature. Answers to such Why X? questions that explain the presence of a characteristic are considered explanations. Throughout the present book, I consider explanations as statements that identify the causes of a biological characteristic or phenomenon, that is, that provide an account for why it happened or

The discussion about purpose and design in Western culture goes back more than two thousand years, at least back to Plato and Aristotle. Plato believed that the universe was created by a Divine Craftsman, the Demiurge (Creator). Plato considered the transfusion of the soul of the Demiurge into the universe as the final cause of its creation. This process had to take into account the actions of Need, the mythical equivalent of the properties of the structure of matter, which imposed constraints to the work of the Demiurge. Plato thus recognized two types of causes, which he viewed as interdependent and not in conflict. Therefore, the universe was an artifact that resulted from the purposeful and rational action of the Demiurge that had dominated over the irrational Need. This is a view of the world being unnatural, in the sense that it is the product not of natural processes but that of a divine craftsman. Aristotle was a student of Plato who tried to answer questions about phenomena in organisms by looking for natural causes. He thus described four causes that acted in nature: the efficient cause, the material cause or matter, the formal cause or form, and the final cause; and he considered all four of them necessary for understanding. The classic illustration of these causes is with the example of a statue: (1) the material cause is the bronze of which the statue is made, which undergoes a change that results in the statue; (2) the formal cause is the shape of the statue, as the bronze is melted and used in order to acquire a particular shape; (3) the efficient cause is the knowledge that the craftsman implements to create the statue; and (4) the final cause is the goal for the fulfillment of which the whole process of the production of the statue is taking place. Even though the example of the statue might make one think that Aristotle thought in terms of design like Plato, this is not the case. For Aristotle, there were no external intentions, and the final causes served the maintenance of an organism. Thus, the final cause for the existence of an organ would be its