3.1 Criteria to Evaluate the Biological Theory of Evolution

In order to evaluate the scientific theory of evolution, we must have some ideas about the nature of science. According to Webster's dictionary, the simplest definition of science is "a branch of study concerned with observation and classification of facts, especially with the establishment of verifiable general law, chiefly by induction and hypotheses." However, there are many different opinions among the philosophers of science concerning the nature of science.

The two extreme viewpoints of science can be represented by the positions of naive realism and idealistic realism (1). Naive realism (positivism) maintains that scientific knowledge is the most positive knowledge and involves the literal description of observations as well as the collection of objective facts. Subjective interpretations are totally dependent on objective facts. Idealistic realism, on the other hand, sees science as entirely the product of human activity, involving tentative models set up in the minds of scientists. Therefore, observations and data are collected by scientists according to presuppositions. However, the objective facts are subject to the interpretation of the scientists, the so-called theory-laden data. Thus, acquisition of scientific knowledge is based on objective and subjective activity.

The scientific method that involves verification or refutation of a theory by empirical observations (provable by experience or experiment) has played an important role in ushering in the modern technological era. Although this method can help man to arrive at only a partial understanding of the nature of reality, the empirical approach is constantly [175] changing, with the result that its ability to describe reality is increasing. Therefore, the empirical method is one of the most important tools in the search for consistent and verifiable explanations of reality.

Scientific methodology consists of careful observation and experimentation with suitable controls. Therefore, the scientist must minimize personal bias during collection and interpretation of data. Sometimes the bias of one influential individual can lead to much wasted effort. This was the case when the powerful Russian agronomist T. D. Lysenko advocated the Lamarckian mode of inheritance, regardless of the overwhelming evidence against it (see Sec. I.1.3.). His opinions controlled scientific research in genetics and agriculture for more than 35 years in the Soviet Union. Not until the serious failure of Soviet agriculture in 1964 did the Russian political authorities withdraw their support from Lysenko (2). However, in the absence of political totalitarianism, science is generally a self-corrective enterprise.

For a scientific theory to be established, it must be a generalization supported by a large body of different types of observations and experiments that are reproducible. In addition, it must have discrete parameters and well-defined concepts so that it is falsifiable (i.e., the parameters and concepts involved must be subject to empirical scrutiny such that their validity can be established or discredited (3)).

Two conditions are inherent in a good scientific theory, empirical adequacy and rational coherency (4). Empirical adequacy pertains to the testability of the theory; it must be amenable to empirical verification. Rational coherency demands that the concept under question be internally consistent as well as consistent with other concepts that are arrived at rationally.

Newton's theory of universal gravitation is a good example of a theory that is both empirically adequate and rationally coherent. It is subjected to empirical verification by every intelligent person who observes the fall of an apple toward the earth, and the calculation of the gravitational constant can be determined experimentally by the Cavendish balance. It is also rationally coherent because it has definable and measurable parameters. In addition, it is consistent with Newton's second law of motion (5).

A theory can be supported by two types of evidence, namely, empirical and circumstantial. Empirical evidence is the data collected by experimental observations and reproducible experience. Circumstantial evidence is data that is proposed as factual, based on reasonable inferences from other accepted facts (e.g., empirical facts). However, the latter can often be interpreted in many different ways, sometimes, resulting in [176] opposing positions. Therefore, empirical evidence is more powerful in the verification or falsification of a theory.

The controversy over the theory of spontaneous generation illustrates the importance of empirical evidence. During medieval times a popular theory stated that life arose continually from the nonliving. This belief was based on circumstantial evidence. People observed worms creeping from mud, maggots crawling from decaying meat, microbes coming from refuse of various kinds and they concluded that this was new life appearing. It was believed also that microorganisms found in spoiled meat broth arose spontaneously from nonliving materials (see I.3.3.1).

It was not until the nineteenth century that Louis Pasteur gathered empirical evidence to demonstrate that microorganisms in the air cause meat broth contamination. He filtered air and identified microscopically the microorganisms trapped in the air filter. He showed also that the trapped microorganisms contaminated boiled sterile broth. Thus, the theory of spontaneous generation under present earth conditions was discredited (see I.3.3.1.a).

The strengths and weaknesses of the Neo-Darwinian evolutionary theory can be evaluated, using the criteria listed above. This author submits that the strengths of the theory lie in microevolution (the special theory of evolution); however, macroevolution (the general theory of organic evolution) has serious difficulties in meeting the above criteria. The validity of microevolution will be evaluated in 3.2 and macroevolution in 3.3.

1. Bube, R. The human quest. Warn, TX: Word; 1971: 50-66.