How does evolution occur? — That is, what natural processes bring new types of organisms into being? Expressed more technically, one might ask, what are the genetic processes that have produced the various forms that scientists recognize and assign scientific names? This is the question considered in the analysis of evolutionary theory presented on this website. There is, of course, a great mass of literature already available on this topic. But my own, more than 20-year investigation of that literature has convinced me that certain widely accepted claims about the nature of evolutionary processes represent little more than unsubstantiated dogma, as unsupported by replicable experiment as the events described in Genesis.
I readily admit that many of the claims made by my fellow evolutionary biologists are in fact correct and entirely reasonable. But some are inconsistent with fact and, in my opinion, the corresponding aspects of evolutionary theory need adjustment. By collecting all the relevant facts together here, I hope to lead you to the same conclusion. It remains true, as R. S. Crane liked to say, that "there is no authority but evidence." On this website I have gathered evidence of all sorts that seemed to have any direct bearing on the question at hand. Moreover, I have tried to present that evidence in such a way that a non-biologist can understand it, so long as he or she reads the information in the order that it is presented. I have done so because I believe the issues considered here are of vital concern, not only to the few people who call themselves evolutionary biologists, but also to humanity as a whole.
For the last 150 years, we biologists have been defending a fortress built by Charles Darwin. We have spent our energies hurling back the assaults of the creationist infidels and shoring up a slowly crumbling foundation that once seemed based on the hard bedrock of direct observation. But an ocean of data, accumulating since 1859, has been slowly lapping away at the rotting stone beneath Darwin's castle, undermining its moldering walls, making it an ever more dangerous place to reside.
As Darwin's most eloquent proponent, T. H. Huxley, once said, "Every great truth begins as heresy and ends as superstition." In the case of evolutionary theory, Huxley appears to have been right. Many of the facts presented in the discussion of evolution on this website do indeed suggest that certain elements of Darwin's heresy can now best be interpreted as a kind of superstition. It was Huxley, too, who warned us not to "pretend that conclusions are certain which are not demonstrated or demonstrable." I will argue that certain important tenets of modern evolutionary theory actually do fall into this category.
I want to present the facts that compelled me to abandon my former ideas of how evolution occurs. As we shall see, a different account of the evolutionary process is far easier to defend on an evidentiary basis than is the one given by most biology texts. According to this alternative view, which I call stabilization theory, certain genetic processes known to disrupt the normal reproductive cycle are the typical source of new types of organisms (a variety of these stabilization processes are described in Section 4 of this website).
Although stabilization theory is a new explanation as a whole, its intellectual components have a long tradition in biological thought, and all the phenomena it invokes are all well known and well documented. Presenting those components, providing examples of the phenomena involved, and discussing the relevant aspects of the history of biology and of biological thought will require many pages of evidence and discussion. But, I suspect many readers will have a very different idea of the nature of evolution by the time they've digested what I have to say.
The orthodox account of evolution is based on the ideas of Charles Darwin and the findings of Gregor Mendel. The most common name for this theory is neo-Darwinism, although it also is known as the modern synthesis (often capitalized), or the synthetic theory. It supposes that in the course of evolution the typical new form arises from a preexisting form via the gradual accumulation of distinctive traits. In other words, the new characteristics are acquired in sequence over time, not all at once. Most of these traits are assumed to be advantageous to reproduction and therefore to accumulate under the influence of natural selection. As Darwin puts it in the Origin of Species,
Whatever the cause may be of each slight difference in the offspring from their parents — and a cause for each must exist — it is the steady accumulation, through natural selection, of such differences, when beneficial to the individual, that gives rise to all the more important modifications of structure, by which the innumerable beings on the face of this earth are enabled to struggle with each other, and the best adapted to survive.²The process of accumulation is usually described as occurring in a population that does not interbreed, or does not interbreed significantly, with other, similar populations. Many people think such a supposition is necessary, because they believe the genetic influence of interbreeding would otherwise prevent the evolving population from accumulating distinctive traits (as we shall see, this is one of the superstitions). Under this scheme, as two populations descended from a common ancestral population become increasingly distinct, they are said to "diverge." They were once the same, but depart from each other in character. The idea of natural selection can be described as follows:
They are naturally selected, just as a breeder artificially selects particular traits. Thus, under this view of the evolutionary process, traits favoring survival and successful reproduction will tend to accumulate over time and bring about changes in the affected form.
This mechanism seems so obvious that it is hard at first to see any way it could be mistaken. The idea of an accumulation of differences resulting in gradual divergence (and ultimately in the production of new types of organisms) is axiomatic in neo-Darwinian theory, and is therefore the orthodox account of evolution. Scientists who hold such views believe evolution is the result of ongoing change within isolated populations (which supposedly causes the divergence of those populations). Thus, two well-known evolutionary biologists, Daniel L. Hartl and Andrew J. Clark (1989: 1), assert that "fundamentally, evolution is the result of progressive change in the genetic composition of a population."
Over the last decade the neo-Darwinian perspective has been extensively criticized, but no one has offered a coherent theory to replace it. Here on this website, however, I attempt to do just that. I also do my best to explain why this alternative theory is preferable to the neo-Darwinian explanation of evolution. The approach I have used in constructing my argument is simple. I identify claims supporting neo-Darwinian theory that are widely accepted, but poorly documented, and then examine them in the light of evidence.
In his book, The Great Chain of Being, Arthur Lovejoy comments that there are
implicit or incompletely explicit assumptions, or more or less unconscious mental habits, operating in the thought of an individual or a generation. It is the beliefs which are so much a matter of course that they are rather tacitly presupposed than formally expressed and argued for, the ways of thinking which seem so natural and inevitable that they are not scrutinized with the eye of logical self-consciousness, that often are most decisive of the character of a philosopher's doctrine, and still oftener of the dominant intellectual tendencies of an age.³
Biologists are no exception to this rule. During the course of my study of evolutionary thought, I became aware that there are indeed certain tacit presuppositions made by many of my colleagues, "ways of thinking," as Lovejoy puts it, "which seem so natural and inevitable that they are not scrutinized." Indeed, for a long time I embraced many of these same assumptions myself. So long as they do escape scrutiny, these presuppositions seem clearly to demonstrate the validity of neo-Darwinian theory. But these claims cannot stand direct examination. If I have properly done my work, by the end of this discussion each such fallacious assumption will have been spelled out and the exact nature of the errors associated with each will have been made explicit.
Let the reader be forewarned, then, that certain conclusions taken for granted within the context of neo-Darwinian theory cannot be taken for granted here. Stabilization theory posits axioms that differ from, and that are even logically inconsistent with, those of neo-Darwinism. Therefore, anyone who accepts the standard view of evolution will have to proceed with caution. The discussion on this website focuses on the validity of axioms. It attempts to show that the axioms on which stabilization theory is based are more valid, that is, are more consistent with available evidence, than are those of neo-Darwinism. Consequently, it will not be possible, nor would it be fair, for the reader to judge between neo-Darwinian theory and stabilization theory merely by considering whether the claims of stabilization theory are consistent with the claims of the standard view. Here the standard view itself is at stake. The discrimination must instead be based on whether available evidence — that is, empirical data — better supports the assumptions of one view or the other. If neo-Darwinism is flawed in its very axioms, then inferences based on that view should not be taken for granted. Therefore, even when the assertions of stabilization theory radically contradict widely accepted claims concerning the nature of the evolutionary process, I ask the reader to look first to the evidence and not to dismiss my claims simply because they conflict with the traditional view.
Hybridization plays a much more important, and a different, role in stabilization theory than it does in neo-Darwinian theory. The word hybrid has been defined in various ways, but a particular definition is well suited to stabilization theory: If two populations are consistently distinct with respect to one or more characters, and if a descendant of matings between those populations is discernibly mixed with respect to those characters, then that individual is a hybrid and any process producing such individuals is hybridization. (Note that population here refers to any set of organisms defined by a particular set of characteristics.) Although hybrids are often less fertile than either of their parents, the degree of fertility varies greatly from one hybrid individual to another, and many are fully capable of producing offspring. For this reason, on this website, the term partially fertile is used to describe hybrids that can produce progeny, since merely saying "fertile" or "sterile" under such circumstances would be misleading.⁴ Typically, they are neither fully fertile, nor entirely sterile.
Most, but not all, of the evolutionary processes posited by stabilization theory involve hybridization, which is the topic of Section 2 (the evolutionary discussion on this website is broken up topically into sections). However, it should be emphasized that the discussion here will focus on the question of how new types of organisms come into being, not on the various neo-Darwinian claims about the significance of hybridization.
The method I follow is to compare at a philosophical level, the relative merits of two explanations of how evolution takes place, stabilization theory and neo-Darwinian theory. That is, once stabilization theory has been fully explained, we will consider (in sections 6, 7, 8, and 9) a series of phenomena, and in the case of each, we will evaluate which of the two theories provides a better explanation.
Not wishing to bore the reader with extraneous considerations, I have tried to limit discussion to those cases where such discriminations can actually be made. To discuss all the phenomena that both theories explain equally well (and there are many) would be both pointless and tedious. So the discussion, as presented here, focuses on those phenomena (and the associated explanations of those phenomena) that will help the reader decide which of the two theories is the better explanation.
Because the processes it emphasizes produce new types of organisms in a relatively rapid and abrupt manner, stabilization theory undermines a primary tenet of neo-Darwinian theory — the claim that evolution is typically a process involving the gradual accumulation of differences within an evolving population. Stabilization theory does not, however, entirely dismiss the mechanisms described in neo-Darwinian theory. It merely claims they are relevant only within a restricted domain, specifically identified in Section 3. It does, however, claim that stabilization processes are the main source of new types of organisms.
This difference in emphasis is justified because such processes are now known to be far more widespread than was once thought. Moreover, the expected pattern of evolutionary change produced by such processes matches the pattern of change actually observed in the fossil record (Section 6). These processes are also far better documented than many of the mechanisms described in neo-Darwinian theory. They therefore can justifiably claim a larger place in theory. The information and arguments presented on this website, then, represent an effort to bring theory in line with currently available data. The discussion reviews empirical evidence both from the standpoint of evolutionary phenomena requiring explanations and from the standpoint of observed phenomena that might provide those explanations.
If you want to read the argument sequentially and see all of the evidence I have gathered to support stabilization theory, you should simply go to the next page (click on "NEXT PAGE" below) and keep reading. However, if you're already familiar with the evidence showing that new types of organisms can be produced rapidly, in one or a few generations (presented in sections 2, 3, 4, and 5), and are familiar with the fossil evidence showing that this sort of evolution is typical (presented in Section 6), then I'd suggest you skip straight to Section 7. It's the first of the four sections focusing on stabilization theory. The first six sections are devoted to presenting evidence and discussing philosophical issues.
But, if you do want to read sequentially, then let's begin in the first section with a discussion of the origin and meaning of species, a word that lies at the center of modern biological thought. NEXT PAGE >>
Introduction - © Macroevolution.net
1. Book I, line 1. Translated by E. M. McCarthy. Original Latin: "In nova fert animus mutatas dicere formas corpora."
2. Darwin (1859: 170).
3. Lovejoy (1936: 7).
4. Even Buffon (1749-1804: XIX, 20) was aware hybrids capable of producing offspring are usually not as fertile as their pure parents.
Introduction © Macroevolution.net