15. Evolution and Complexity

Definitions

Evolution (in the general sense) the process through which new structures, behaviors or concepts come into being from previous ones with, generally, an increase in complexity.

Evolution (in the biological sense) the process by which new species of living organisms develop from older forms by genetic transmission of slight variations preserved by natural selection.

Natural selection in the biological sense) the process through which those genetic variations that assist in survival and reproduction of organisms are passed on to succeeding generations. Those variations that do not assist survival lead to extinction.

Natural selection (in the general sense) the process that enables the existence of those simple systems that succeed in achieving the lowest energy level consistent with the maintenance of their structure. Or, in the case of complex systems. those that make most efficient use of energy tend to continue their existence and drive out those that do not.

Background

Darwinian evolution is the grand organizing principle in biology. The word evolution is therefore strongly associated with the development of living forms. But astronomers speak of the evolution of stars and galaxies from unorganized matter and of the evolution of the universe itself. Social scientists discuss the evolution of modern societies from less complex forms of human organization. Historians of technology refer to the evolution of products; the telephone, for example.

The use of the same word to describe these widely different products and processes of change implies some sort of relationship among them. General systems theory and the study of self-organizing systems would authenticate this relationship.

Discussion

On the most basic level, the laws of physics are such that a uniform distribution of matter tends to be unstable. Under the influence of the organizing principles of electromagnetic attraction and gravity matter tends to aggregate into structures. Thus are born elementary particles and galactic systems. Bracketed between these widely different scales of development there are the successive evolution of stars, of planetary systems, and of chemical, biological and cultural systems. Overall, evolution, in the general sense of the term, tends in time to produce more highly organized patterns. This disposition of the universe toward organization appears to run counter to the well-known tendency toward breakdown and uniformity embodied in the 2nd law of thermodynamics. (more on this in Section 19)

From a broad point of view one kind of evolution gives birth to others; an evolution of evolution. Chemical evolution precedes biological evolution which must, of necessity, be the forerunner of the evolution of social organizations.

Complexity evolving

W. Brian Arthur writing in Scientific American (May, 1993) Why Do Things Become More Complex? advances the idea that the secret of evolution is the continual emergence of complexity. Although complexity is one of those concepts that are hard to define, we know it when we see it. From weather systems to organisms to smart phones to economic markets, complex systems are all about us. We do not have any trouble recognizing relative complexity when we say that one thing is more complex than another. Who would disagree with the statement that chess is a more complex game than checkers?

Questions arise however: where did complex systems come from and why are there so many of them? As mentioned before, systems that more successfully respond to stress and change take the place of less competent systems. This usually is accomplished by an increase in complexity of structure or of behavior. Arthur points out that some systems adapt and improve performance by the addition of subsystems and he suggests that a general law of evolution exists: complexity tends to increase as functions and modifications are added to a system. The functions and modifications are those behaviors and structures that, in the physical realm, make the system better able to maintain itself against thermodynamic breakdown and, in the biological realm, better able to reproduce.

As an example of this increase in complexity which increases viability is the emergence of cells with enclosed nuclei (eukaryotic cells). They are vastly more complex than the bacteria that live without enclosed nuclei (prokaryotic cells). The modern theory of cell evolution maintains that the complexity of eukaryotic cells is due to successive entrapments of various simpler prokaryotic cells. The different functions of the ingested cells account for the multitude of behaviors and structures of the captor cells. These more complex cells are the basis for all multicellular organisms. Without this evolutionary change there would be no animals or plants on Earth today.

Evolution and Complexity a critical view

Stephen J. Gould (Scientific American, Oct. 1994), the late eminent paleontologist, maintained that the idea that evolution is an increase in complexity is a bias inspired by parochial focus on ourselves, and consequent over attention to complexifying creatures. He suggested that the evolution of parasites is an example of successful movement away from complexity. In addition, he strongly objected to the representation that the history of living organisms is a sequence leading to humankind. He took exception to the illustrations in museums and textbooks that show a progression of living forms from invertebrates to fish to reptiles to mammals. In his view it neglects the fact the most successful and most numerous organisms are still the simple prokaryotic cells.

Bacteria live in every conceivable habitat on and in the Earth. They also exist in some places we would think incapable of supporting living organisms like hot sulfur springs, volcanic vents in the ocean floor, or within rock layers deep underground.

Gould objected to the idea that biological evolution in any way could be called progressive. He noted the long period of time, almost 3 billion years, when the only forms of life on Earth were onecelled organisms. The first multicellular animals appeared less than 600 million years ago. He argued that our continual desire to view history as progressive, and to see humans as predictably dominant, has grossly distorted our interpretation of lifes pathway.

According to Gould, every once in a while, a more complex creature evolves and extends the range of lifes diversity in the direction of increased complexity. But the movements toward greater complexity he says are rare and episodic and do not constitute a series. Rather they are, in his view, accidental tumblings into the region of complexitys space while, as time passes the number, the variety and indestructibility of bacteria continue to increase. He points out that there is very little empirical evidence to show that increased complexity is the thrust of evolution. He concludes that for each mode of life involving greater complexity, there probably exists an equally advantageous style based on greater simplicity of form.

Responding to Gould

It is certainly true that the adaptable bacteria will outlast human beings just as they have outlasted so many other species in the history of life forms on our planet. Complex organisms share with complex machines the increased likelihood of malfunctioning. An environmental catastrophe can, and has, wiped out hundreds of thousands of complex species. As long as the Earth orbits the Sun, bacteria will probably grow and prosper. Yet it is the conviction of many scientists that once the threshold of multicellularity is crossed, complex plant and animal forms inevitably arise that, far from being accidental, as Gould argues, the development of complex organisms is to be expected, although their exact forms may be a matter of chance. Admittedly, there is a paucity of scientific studies that show increased complexity as the inevitable consequence of evolutionary change, just as there is very little scientific evidence against it. The study of the complex is very difficult. Part of the problem is that we have no scientific approach to problems involving coincident action when many variables act through many feedback loops. Our studies are generally limited to linear problems. Isolation and the study of one variable at a time is the laboratory rule. We need a biological calculus that will facilitate the study of how complicated things change under multiple and simultaneous influences. Perhaps when we have such a calculus more exact studies of complex systems will appear.

The problem with "progress."

The idea that evolution represents some kind of progress in the world is one which has been superseded. The term progress is too subjective to be useful. It is too closely related to something that is presumed good for humans. However, there is a sense in which the word progressive can legitimately be applied to evolution. If we remove the value judgment and define progressive evolution to mean only that structures later in time build on features of those that have gone before, then evolution is progressive. The new includes the old as, for example, the vestigial organs that survive in all of us.

From chance alone - to chance plus self-organization

It was not so long ago when, in our biology classes, we taught that the origin of living systems was due to a chance encounter of complex molecules in some primordial amino acid soup in some warm, tidal pool. Darwin himself thought the development of adaptive characteristics was due to the slow accumulation of chance changes. Our students were told that the long expanse of geological time provided the opportunity for natural selection to make the fit of organisms so precise.

The study of self-organizing systems can provide a different point of view. The tendency toward self-organization may turn out to be the helpmate of natural selection.

Organization emerges

Consider the simple case of crystal formation. By chance a solution of molecular components may experience conditions of density and temperature which make crystal formation possible. But once these conditions have been met the molecules will, by virtue of their inherent properties align themselves into particular spatial relations and form a crystal. The point is that the formation is not due to the random encounters of particles. The crystalline order emerges from the solution whenever conditions are right, a self-organizing process. The same may apply to the formation of living material.

When the evolution of inanimate matter to living organisms is presented solely as a result of natural selection working on random changes under the stress of environmental change, it seems a completely accidental process. Although natural selection of random mutations is a necessary condition for evolution, it may not be the only influence. As will be discussed in Section 17 , Cells - Self Organizing Systems, several processes may have been at work to produce the first living cells.

From the organization of molecules, to the folding of proteins, to formation of cells, the tendency toward the development of complex self-organizing systems gives natural selection material to work with. Thus, it seems, chance and organizational tendencies may be cooperating partners.