The Factors of Organic Evolution

Abstract

WHILE reviewing, a short time ago, Mr. Herbert Spencer's essay on the above subject (NATURE, vol. xxxv. p. 262), I promised to consider the present standing of the question as to whether, or how far, use and disuse admit of being regarded as true causes of change of organic type. Of course there is no question about the effects of use and disuse as regards the individual: the only question is as to whether, or how far, these effects admit of being inherited, so that modifications of structure which are produced by modifications of function in the individual become causes of corresponding, and therefore of adaptive, changes of structure in species. The importance of this question is second to none in the whole range of biology. For not only is it of the highest importance within the range of biology itself— governing, by whatever answer we give it, our estimate of the importance of natural selection, and thus requiring to be dealt with on the very threshold of biological philosophy—but its influence extends to almost every department of thought. For, as Mr. Spencer remarks in his preface, upon the answer which this question may finally receive will depend in chief part the sciences of psychology, ethics, and sociology. If functionally—produced modifications are inheritable, the phenomena of instinct, innate ideas, moral intuitions, and so forth, admit of a scientific explanation at the present moment; otherwise they do not, or, at least, not in so distinct nor in so complete a manner. Therefore, we can hardly feel that Mr. Spencer exaggerates the importance of this question when he says of it, “Considering the width and depth of the effects which our acceptance of one or other of these hypotheses [namely, that functionally-produced modifications are inherited, or that they are not] must have upon our views of Life, Mind, Morals, and Politics, the question—Which of them is true? demands, beyond all other questions whatever, the attention of scientific men.”