The Theories of Darwin and Their Relation to Philosophy, Religion, and Morality | Page 8

and thus led of itself to the evolution theory. As soon as the naturalists thought they had found the causes of such an evolution of the species, they naturally placed these causes in the foreground of their demonstrations, and erected upon them the structure of their entire theory; thus treating descent, evolution and selection as one single and indissolubly connected theory. But this manner of treating the question had also its dangers, which have already caused a great deal of confusion and misunderstanding, as well as much unprofitable controversy. Often friends and enemies of the theories placed that which was in favor of the theory of descent to the credit of the evolution or selection theory; and, on the other hand, that which seemed opposed to the selection theory was often held to be a weakening of the evolution and descent theory; and this was done, not only by amateurs, but often enough by the highest authorities also. In reality, however, it is quite conceivable that the idea of a descent may prove correct, and possibly the idea of an evolution of the species will have to be replaced by that of a heterogenetic generation, or by the theory that certain groups in the organic system are originated {29} by heterogenetic generation, and others by evolution; and so the evolution theory must share with the theory of heterogenetic generation, or of a metamorphosis of germs. On the other hand, it is conceivable that even where the evolution theory is confirmed, the evolution can be accounted for wholly or partly by other reasons than those derived from the selection theory. And even this result of present investigations is not inconceivable: that the reasons for and against the different theories will be found to balance one another to such a degree that they will sooner or later lead science, in answering the question of the origin of species, to the old confession of Socrates--"Ignoramus."
We shall, therefore, have to arrange our historical sketch according to the historical order of the appearance of the theories, and treat the problems more or less as an undivided whole. But we shall keep in mind, during our historical sketch, not only the logical separation of the problems in question, in order not to lose clearness of judgment, but we shall also at the end of our review, if we consider the present condition of the problems, have to examine the same once more in detail, so far as regards the above mentioned separation.
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CHAPTER I.
RISE OF THE DARWINIAN THEORIES.
�� 1. Direct Predecessors.--Lamarck.
The first man who gave direct expression to the idea of a successive generation of the species through transmutation, and who attempted to follow it up in a scientific way, was the French naturalist and philosopher, Jean Lamarck, born 1744. In the year 1801, and subsequently, he published his views, first in smaller essays and afterward more in detail in his "Philosophie Zoologique," which appeared in 1809, and in the first volume of his "Histoire Naturelle des Animaux sans Vert��bres," published in 1815. In these works Lamarck upholds fully the descent and evolution theory, and maintains that the simplest organisms are generated through a generatio spontanea, which is still taking place; but that all the more developed organisms, including man, are descended through a gradual change from other species. With this theory, he put himself in direct and conscious opposition to the old doctrine of the immutability of species and their characteristics, which had been ably maintained by Linn?us, and also made some attempts at explanation which approach very nearly the selection theory. A change in the physical conditions of life, especially the force of habit in the use or disuse of the organs, the inheritance of physical and psychical {31} qualities thus attained, and the extension of the process of transmutation into extraordinarily long periods of time with very slight changes, are also, in his view, the probable causes of the variation and development of the species. He only lacks the idea of a natural selection in the struggle for existence, and the comparison of the processes in nature with the methodical selection of man in the breeding of domestic animals and plants, to identify his views with those of Darwin.
At first, Lamarck met only with violent opposition; but after a little while his views ceased to attract attention. The time had not yet come to make such an attempt at observing nature from the standpoint of evolution. The sciences which favor such a mode of observation, and even demand it--such as comparative anatomy and physiology and the history of the development of the different plants and animals--were only in their infancy, or were--like pal?ontology and the comparative geography of plants and animals--not yet in existence. The influence of Linn?us, whose views