Age and area; a study in geographical distribution and origin of species,

Abstract

Some thirty years ago, a pupil of the strictest school of natural selection, and enthusiastic in my belief in its principles, I set out upon a course of independent observation of nature.Ten years of such work convinced me that a simpler explanation of phenomena was always to be found, and one that seemed more in accordance with the facts; and I endeavoured-with what success this book will show-to free myself from the trammels of the natural selection theory, and to work as if I had found myself in another planet where scientific investigation was just beginning.Stationed in one of the best centres in the tropics (where the phenomena of distribution are more impressive than in Europe), badly handicapped in laboratory work by a serious accident, and finding my chief pleasure in travellingabout the world to see its vegetation-I took up the study of distribution, in which I had always taken much interest.Here, as elsewhere, it was soon evident that the current theories provided an explanation that was not only unnecessarily complex, but one that did not explain.As one of my critics words it, "for some reason the plant has advantages which enable it to spread"; and beyond that point we cannot go.Gradually it became clear to me that plants spread very slowly, but at an average rate determined by the various causes acting upon them, so that age forms a measure of dispersal when one is dealing with allied and similar forms.Age as an explanation of spread is enormously simpler than natural selection, and that it is probably valid is shown by the way in which it can be used for prediction.An opponent re- marks that "it is too simple to be true," but this very simplicity seems to me a strong reason in favour of its adoption, at any rate as a preliminary hypothesis.Of two explanations take the simpler, is an old rule, and as Hooker has said, "no speculation is idle or fruitless, that is not opposed to truth or to probability, and which, while it coordinates a body of well-established facts, does so without violence to nature, and with a due regard to the vi PREFACE possible results of future discoveries."To find explanation of the facts of distribution under the current theories has always seemed a very hopeless task, and any hypothesis that offers a way out should at least receive attention.No hypothesis can, after all, alter the facts, though it may show ways in which to accumulate new ones.In the second part of the book, I have pushed my hypothesis to what seem to me its logical conclusions, conclusions which are sometimes subversive of received opinions.To be compelled