Science in Christian Perspective

Comments on the Origin of Species*
J. FRANK CASSEL**

From: JASA 13 (June 1961): 42-45

Introduction

In the fall of 1959 the centennial of the publication of Darwin's Origin of Species (1859) was celebrated at the University of Chicago. Only recently the proceedings of these meetings, including lectures, papers, panels, and general discussions, have been published in three large volumes (Tax, 1960; Tax and Callender, 1960). These volumes summarize what is known about the subject of evolution and what some of the greatest minds of our time are thinking about it. Volume 1, the largest,

*Condensed (and supplemented) from a tape recording of an address given from notes 17 Feb. 1961 as part of the Wheaton College Symposium on "Origins and Christian Thought Today."

**Dr. Cassel is President of the American Scientific Affiliation and is Chairman of the Department of Zoology, North Dakota State University, Fargo, North Dakota.

in 629 pages and 20 papers, deals formally with the subjects Dr. Hearn and I are discussing. Obviously we cannot do the field justice in one hour.

I have not had these volumes long enough to be able to summarize them for you. It was only this morning, in fact, that I came across a paper (Olson, 1960: 523-545), which questioned what I had felt was the generally if not universally accepted trend of the field. If then my presentation seems somewhat disjointed, it is partially because I have not yet adjusted my own thinking to these new idea - I have seen my paper for this afternoon-as it were -go up in steam.

What is our purpose? What can we do here? It seems to me that the advantage of a gathering such as this is to find out what is being thought-to assess the facts that we have-to assess the interpretations of these facts not only in the light of themselves but in the light of the presuppositions that we make. I don't want to stand here today-in fact I'm not able to stand here and tell you what you should believe. But I think that here we can exchange ideas and thus come closer to a recognition of reality.

Over a hundred years ago (1831-36) Darwi sailed around the world in the Beagle. A short time after that ' he tells us in his introduction to the Origin of Species (1859 (1909:21) ) he began to keep notes-and after five years, he says, he allowed himself to think about what some of these observations might mean and two years later (1844) sketched some conclusions. It was some 15 years after that that the Origin of Species was published. I beleive the Origin of Species had the influence upon the biological and the rest of the world that it had, because of the intricate documentation that Darwin gave, showing the background of his ideasstimulating other people to take this data and see what they could get out of it-stimulating others to find out more data and see how it would correlate. And so for a hundred years in various disciplines this has been done. Thus a great body of data has been accumulated, which formed the basis of the Chicago discussions and forms the basis of our discussions today.

Origin

"Origin" or "origins" may be self-explanatory. This is not the key word in our discussion. Origin refers to the beginning. Where did something start?

"Species" is defined in various ways. Perhaps the problem is best summarized by Mayr (1956) when he points out that there are three different species concepts.

1. Species can be thought of from the standpoint of a type. A biologist describes an animal. He says, "Hereafter this species will consist of all animals which are like this animal which I am describing which I will deposit in this museum." Thereafter a decision must be made with respect to any unknown animal as to whether it is enough like the one on deposit at the museum and like the original description to be called the same species, or whether it's different. This is the classical idea of species.

2. A second idea of species is based on concept. (This is my own term, not Mayr's.) It suggests that if we say "robin," for instance, each one of you in your mind gets a picture of a robin. It isn't a particularly detailed technical picture, but at least you know what a robin is.

3. The third view of species we call biological. This one is most useful in the discussions w~ are having. The biological species is conceived as a group of animals having a certain genetic make-up, the elements of which can be passed on to their offspring maintaining essentially the same genetic make-up. Hence, a species is a group of naturally occurring populations which freely interbreed at the periphery of their ranges (where they come together), or are potentially capable of doing so. Or, briefly, a species consists of those animals which freely breed with one another.

The division between species comes then when interbreeding cannot occur for some reason or other. This would seem rather easy to observe. But we find that there are some organisms which are partially fertile with other organisms. We also find organisms which are identical in their morphology and their external appearance, but cannot interbreed. We find other organisms which look very different in their outward appearance, but which do interbreed freely. We find all the spectrum in between these. So this is not an easy criterion.

What does "kind" mean as it is used in Genesis? I am not posing as an authority on this but in discussions that I have seen of this word it is taken often to refer to a certain category of organisms (Mixter, 1951:3; Bullock, 1952; Payne, 1957), but not consistently to any specific biological category. Oftentimes, I think, we create a problem by saying (or thinking) that "kind" must refer to "species." Undoubtedly "kind" sometimes does refer to species. But "kind" also may refer to other groups, perhaps to genera, perhaps to families, perhaps to higher categories. So that it is not accurate, it seems to me, to restrict the use of "kind" to species.

Origin of species-how could it take place? Darwin suggested, arguing from indirect or circumstantial evidence, that it seems as if it has in some cases by natural means. We know a great deal more about the possible mechanisms by which species might be formed than did Darwin. Our knowledge of chemistry is much greater (Hearn, 1961). What are these mechanisms whereby species could be formed? Is there a mechanism whereby organisms which can at one time freely interbreed might at another point of time not be able to interbreed? If such a situation can be shown to obtain, then we can say that species have been formed and that speciation has taken place. And the word that we use in the field to talk about this is evolution.

Evolution means a number of things to a number of people. I raised my eyebrows when I saw that this symposium was going to be on "Origins and Christian Thought Today." We're talking about the book, "Evolution and Christian Thought Today" (Mixter, 1960). Perhaps "origins" is a much better word, because we all are in fair agreement as to what it means. On the other hand, practically every one of us has a different idea of what the word "evolution" means.

Indeed the word does have several meanings which are currently used in scientific or other literature. Some of the main ones follow.

1. Evolution is the process whereby all life has developed by mechanistic means without God from single cells or primordial protoplasm to all the different forms we have today. But with such a definition (equating evolution with atheism), if this be the only one allowed-as many affirm-we as evangelicals are left with no satisfactory word to use to describe the phenomena relating to species fonnation, phylogeny, and similar scientific data.

2. Evolution is the general theory that life as we know it on earth today has over a long period of time been developed by differentiation from a single or several primordial cells; descent with modification.

3. Evolution is any change in plants or animals which can be passed on to their offspring. Many writers say or infer that such changes must take place "in natural populations" to get away from the discussion of the significance of changes due to controlled breeding practices. Mayr (1959) puts it, "Organic evolution . . . refers to a change in genetic properties from generation to generation owing to reproduction." It is this connotation of the word which is most commonly intended, when modern writers discuss evolution in action. According to this concept evolution can be either progressive or retrogressive. In other words, the change may go toward the complex or toward the the simple.

4. One thing that evolution does not mean is that man descended from apes. The word may be used to refer to the idea that man and apes may have descended from some common ancestor. But straight line descent from anthropoid ape to man (or any other straight line descent) is no longer inferred.

I have often seen the word "evolution" used in the same paragraph in the same article several times with a different connotation each time. Therefore it is very difficult to talk about "evolution" and to understand just exactly what we mean when we're talking about it.

Speciation

What do we know more than Darwin knew about the formation of species? We know about genetics. We know something of the intricacies of cellular structure. We know much of the biochemistry of the cell, particularly of the nucleus. We know something of the operation of the particular factors which seem to influence the heredity of the organism.

Isolation

In a population of freely interbreeding organisms in nature a change within one organism is not likely to affect the population unless something happens to favor the maintainence of this particular change. There are so many other genes in any group, or gene pool as we call it, that one mutation in and of itself has no effect upon the population, because the mutant gene does not often even come into enough abundance to be seen, that is to effect an observable change in any organism. In artificial breeding, if we find a characteristic in a plant or animal which we want to keep, we then separate or segregate this individual and breed it only to other individuals which have other characteristics whch we want to keep. In other words, these individuals have to be isolated. In the process of speciation (species formation) in nature, this is another necessary factor. The population must be so small that mutations will be maintained because the mutant genes form a significant portion of the genes in the gene pool.

Natural populations of organisms may be isolated or separated from other such populations by geographical barriers such as mountains or rivers, by habitat preference, by climatic responses, and eventually by morphological or physiological differences. Species, however, are not formed until reproductive isolation is developed, that is until the separate populations are no longer even potentially capable of interbreeding. There are numerous examples of this occurring in nature. Perhaps the most striking one is the circumpolar distribution of overlapping populations of gulls of the Herring Gull-Brown Gull complex. In Scandinavia the Brown Gull does not interbreed with (is reproductively isolated from) the Herring Gull and yet each population does freely interbreed with adjacent populations all round the pole in a continuous ring broken only where the Brown and Herring Gulls maintain distinct populations where they overlap in northern Scandinavia. (See Mayr, 1940).

In artificial breeding, we select for those factors which we want. Darwin suggested that this same thing happens in nature. With the proper isolation, selection can be achieved. He suggested that if any change in the organisms was of particular advantage to that organism, this would give that organism greater strength to carry on its life than if this change had not occur-red. Actually it does not appear that great advantage is a necessity for the effective selection and development of a characteristic in an isolated population. It is obvious that if any change occurs in a plant or animal which is of disadvantage to it, that individual is not likely to exist or reproduce as well as it would otherwise. (The human species is an exception, because much of our medical work maintains life in those individuals that are not as well adapted to the environment as others). On the other hand, in nature, if there is a change within a small population which is sufficiently isolated, this change can be maintained without any great advantageous selection. But if there is a factor which is of advantage to the existence of the organism so that it breeds more freely or produces more offspring which then contain these same genetic characteristics, this particular genetic characteristic is likely to be developed with a greater frequency than those which do not have such an advantage. It is usually held t at such changes are quite slight (microevolution) and that it may take several to effect much visible change in the individuals of a population. It should be remembered, too, that speciation is not accomplished until reproductive isolation is established no matter how great or how little the other changes involved. This then very briefly, and sketchily, delineates the thinking at the present time of those who hold to the "synthetic theory." I have pointed out elements or mechanisms which must be considered by anyone contemplating on how changes might come about in populations of organisms.

In the paper 1 came across this morning, the author makes a point which is seldom emphasized. In our present state of knowledge he suggests that it is presumptuous in the face of a variety of interpretations of the data to hold that there is only one interpretation possible. "The statement is made, in effect, that those who do not agree with the synthetic theory do not understand evolution and are incapable of so doing.... Regardless of the apparent merit and strength of the synthetic theory, it seems to me that the more cautious and thoughtful attitudes ... are more appropriate" (Olson 1960:526, 527). He then gives the several theories which must be considered.

Olson includes the alternative of a Metaphysical Theory of Evolution. The discussion which we have here at this symposium w1l be along the lines, I hope, of developing in a sound way some real contributions to this alternative. This, ladies and gentlemen, I suggest is our challenge as evangelical Christians. May we stop shadow-boxing. May we stop finger-po~inting. May we be careful not to fall into the same fallacy for which Olson chides the synthetic evolutionists. From our Christian presuppositions of the creating and sustaining God, may we work eagerly to develop without apology an explanation for the biological phenomena which we see in the universe. Particularly with regard to the phenomenon of speciation, or the origin of species, should we do some of our most careful observation and our best thinking so that we can prepare as accurate and true a description of the reality as presently possible in the light of presently discernible revelation.

Bullock, W. L., The "kind" of Genesis and the "species" of biology. J. Am. Sci. Affil. 4:5-7. 1952.

Darwin, C., On the Origin of Species by Means of Natural Selection. London. 1859. Reprint: The Harvard Classics, C. W. Eliot. 1909. Collier, New York.

Goldschmidt, R., The Material Basis of Evolution. Yale, New Haven. 1940.

Hearn, W., Origin of Life. J. Am. Sci. Affil. 13:38-42. 1961.

Mayr, E., Speciation Phenomena in Birds. Am. Nat. 74: 249-278. 1940. Ecological Factors in Speciation. Evolution 1:263-288. 1947. Species Concepts and Definitions. AAAS Publ. 510:1-22. 1957. Darwin and Evolutionary Thought, p. 1-10. In Evolution and Anthropology, a Centennial Appraisal. Gaus', Brooklyn. 1959.

Mixter, R., Creation and Evolution. Am. Sci. Affil. Mono. 2:1-31. 1951. Evolution and Christian Thought Today. Eerdmans, Grand Rapids. 1959.

Olson, E. C., Morphology, Paleontology and Evolution. Pp. 5231545. In Tax (ed.) Evolution after Darwin. Chicago U., Chicago. 1960.

Payne, J. B., The concept of "kinds" in Scripture. J. Am. Sci. Affil.-10:17-20. 1957.

Tax, S., ed., Evolution after Darwin. Vol. 1. The Evolution of Life. Chicago U., Chicago. 1960. Vol. 2. The Evolution of Man. Chicago U., Chicago, 1960.

Tax, S. and C. Callender, ed., Evolution after Darwin. Vol. 3. Issues in Evolution. Chicago U., Chicago. 1960.