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The Story of Evolution, Spring 2005
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Mayr began the section on evolutionary progress in his book What Evolution Is with the statement that "Evolution means directional change" (p. 212). But in which direction is evolution going? Towards what objective is it moving? The idea of perfection has been rejected by evolutionists (Mayr 213), so evolution must not be moving towards an ideal. The issue of progress in evolution is a very complex and subjective one that is greatly dependant on the definition of progress. Mayr acknowledged the problem with defining progress, yet in the end settled with the idea that the process of evolution usually involves progress. I will argue that evolution does not involve progress, even within specific lineages. The two main components that lead to the process of evolution—random variation and differential reproductive success—do not combine to create an ordered progression that improves with change. The former depends on randomness, and the latter on the environment, which is constantly in flux. Hence evolutionary change leads to continual difference, but no variation is better than any other one. The words "progress" and "better" should be abandoned in evolutionary discourse, because they refer to processes that do not occur in nature.
The first task when examining the possibility of evolutionary progress is to define the term progress. Francisco Ayala wrote that progress "contains two elements: one descriptive, that directional change has occurred; the other axiological (evaluative), that the change represents betterment or improvement" (Taylor). The concept of directional change implies a linear trajectory towards some objective. But is evolution moving towards anything? Evolution is not headed towards perfection, since there is no underlying designer, according to the currently accepted scientific theory of evolution. In addition, perfection is an indistinct concept that doesn't really exist in the natural world, so it should not be used in this context. Mayr stated that evolution has no specific goals, yet he still believed that progress occurs within specific lineages. This seems paradoxical—if evolution isn't moving towards anything, how can it be progressing? The second part of Ayala's definition, concerning improvement, is highly subjective. Scientifically, no species can be viewed as "better" than any other. Each species adapts to fit into a certain niche, and its success depends on a variety of factors, such as environmental conditions, relations to other species, and so on, many of which have little to do with whether the species is "better" than others.
The notion of progress implies that something is increasing—complexity, intelligence, efficiency, success, etc. There are several processes that have occurred over the course of organism evolution since the beginning of life that cannot be easily refuted, including increased complexity and diversification. These processes are presumed because life is believed to have begun with "simple" single-celled organisms, so organisms that exist today can be described as more complex and more diversified. This change towards greater complexity and diversification was inevitable because of the nature of the beginning of life. Life as we know it cannot get any simpler than prokaryotes, so change had to lead to greater complexity (Turner 111). But these changes do not mean that progression has occurred. The word progress implies a certain improvement that isn't assumed with increasing complexity and diversification. Complex species like mammals are not any "better" than bacteria in terms of survival and reproductive success.
A more complex issue within the idea of progress is increased efficiency and success (expansion of species, ability to live in more variable conditions, resistance to extinction). It is difficult to deny that there have been specific developments within specific organisms which increase their efficiency, for example in obtaining food or reproducing. But there is no distinct trend of continuously increasing efficiency in organisms. Efficiency is directly dependent on environment, which is highly variable and constantly changing.
When one defends the idea of progress within evolution, progress is explained as a large-scale trend (Turney 110). According to Mayr, evolutionary progress is a general trend within many lineages. However, it can't be described as a universal trend because simplification and regressive evolution occur in addition to "progressive" evolution (Mayr 213). I don't believe that "trend" is a useful term when analyzing the process of evolution. Trends imply a type of order an linkage hat is not present in the randomness of evolution.
The nature of the process of evolution specifically prevents it from producing any real "progress". Evolution, in its simplest explanation, is due by random variation followed by differential reproductive success. The differential reproduction is in relation to current environmental conditions, which are local and transitory. The adaptation to local environments due to natural selection does not constitute a global trend (Turney, 109). This adaptation to specific environmental conditions is not better than adaptation to previous environments, so current species are no better than the forms that they took in the past. In addition, Mayr fails to emphasize the importance of randomness in the process. The random variation that occurs has much to do with the direction that evolution takes, thus preventing it from going in one specific linear, "progressive" direction.
Words like "progress," "improvement" and "better" are carried over from the old notions of the Great Chain of Being and the idea that evolution strives for perfection. These ideas are no longer accepted by evolutionists, so the terms associated with them should be removed from evolutionary discourse. This old terminology hinders our understanding of the randomness of evolutionary processes. Darwin's theory itself did not deal specifically with the idea of evolutionary progress (Taylor) and I don't believe that it should be part of the story of evolution that is told today. Even when limited and qualified, progress is not an appropriate or useful term to use in the discussion of evolution. Evolution is constant change, not improvement.
Stewart, John "Evolutionary Progress" http://www4.tpg.com.au/users/jes999/evpro.htm
Taylor, Tim "Evolutionary Progress" (1999) http://homepages.inf.ed.ac.uk/timt/papers/thesis/html/node21.html
Turney, Peter "A simple model of unbound evolutionary versatility as a largest-scale trend in organismal evolution" Artificial Life 6 (2) 2000 p. 109-128. http://cogprints.org/1799/
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