Orthogenesis - Collapse of The Hypothesis

Collapse of The Hypothesis

The orthogenesis hypothesis began to collapse when it became clear that it could not explain the patterns found by paleontologists in the fossil record, which was non-linear with many complications. The hypothesis was generally abandoned when no mechanism could be found that would account for the process, and the theory of evolution by natural selection became the prevailing theory of evolution. The modern evolutionary synthesis, in which the genetic mechanisms of evolution were discovered, refuted the hypothesis for good. As more was understood about these mechanisms it became obvious that there was no possible naturalistic way in which the newly discovered mechanism of heredity could be far-sighted or have a memory of past trends.

The orthogenetic hypothesis, however, died hard. Even Darwin was at first not opposed to orthogenic thinking, as this quote from the 1911 Encyclopædia Britannica demonstrates:

Darwin and his generation were deeply imbued with the Butlerian tradition, and regarded the organic world as almost a miracle of adaptation, of the minute dovetailing of structure, function and environment. Darwin certainly was impressed with the view that natural selection and variation together formed a mechanism, the central product of which was adaptation. From the Butlerian side, too, came the most urgent opposition to Darwinism. How is it possible, it was said, that fortuitous variations can furnish the material for the precise and balanced adaptations that all nature reveals? Selection cannot create the materials on which it is supposed to operate; the beginnings of new organs, the initial stages of new functions cannot be supposed to have been useful. Moreover, many naturalists, especially those concerned with palaeontology, pointed to the existence of orthogenetic series, of long lines of ancestry, which displayed not a sporadic differentiation. in every direction, but apparently a steady and progressive march in one direction.

Edward Drinker Cope put such a line of argument in the most cogent fashion; the course of evolution, both in the production of variations and their selection, seemed to him to imply the existence of an originative, conscious and directive force, for which he invented the term bathmism (Gr. βαθμ, a step or beginning). On the other hand, dislike of mystical interpretations of natural facts has driven many capable naturalists to another extreme and has led them to insist on the all-powerfulness of natural selection and on the complete indefiniteness of variation. The apparent opposition between the conflicting schools is more acute than the facts justify.... there is no connection between the appearance of the variation and the use to which it may be put... in one sense it is a mere coincidence if a particular variation turn out to be useful. But there are several directions in which the field of variation appears to be not only limited but defined in a certain direction. Obviously variations depend on the constitution of the varying organism; a modification, whether it be large or small, is a modification of an already definite and limited structure.... A continuous environment both from the point of view of production of variation and selection of variation would appear necessarily to result in a series with the appearance of orthogenesis. The history of the organic world displays many successful series and these, as they have survived, must inevitably display orthogenesis to some extent; but it also displays many failures which indeed may be regarded as showing that the limitation of variation has been such that the organisms have lost the possibility of successful response to a new environment.

A few hung on to the orthogenesis hypothesis as late as the 1950s by claiming that the processes of macroevolution, the long term trends in evolution, were distinct from the processes of microevolution (genetic variation and natural selection) which were by then well understood and it was known they could not behave in an orthogenetic manner. Teilhard de Chardin, a Jesuit paleontologist, in The Phenomenon of Man (a book influential among non-scientists that was published four years after his death in 1959) argued for evolution aiming for the "Omega Point", while putting man at the center of the universe and accounting for original sin (Dennett 1995, von Kitzing 1998). The term Chardin used for this was "directed additivity". This form of orthogenesis has now also been abandoned as more about evolutionary processes has been discovered (Wilkins 1997).

The refutation of orthogenesis had some ramifications in the field of philosophy, as it refuted the idea of teleology as first postulated by Aristotle and accepted by Immanuel Kant, who had greatly influenced many scientists. Before the scientific and philosophical revolution that began with Charles Darwin's ideas, the prevailing philosophy was that the world was teleological and purposeful, and that science was the study of God's creation. The refutation of these concepts have led to a shift in what science and scientists are perceived to be.