Title: On the Faunal Position of the Pacific Coast of the United States
Abstract: The fauna of the Pacific Coast of the United States is of unusual interest and presents many fascinating problems. Intimately connected with practically all of these in one way or another is the matter of climate, past rather than present, for the reason that the latter is of but transitory import to the life of a species. There are to be found clues regarding the climate of several stages of the later Pleistocene and recent times which suggest certain conclusions pertinent to the status of the fauna of this region and these are worthy of consideration, while at the same time bearing in mind that they can be no more than theories until far more data are available than are now at our disposal. Concerning the climates of preglacial times I venture no opinions. Broadly speaking, evolutionists seem to agree that the higher organisms are now in a state of evolutional quiescence with comparatively little change of characters in progress. Whether or not this be fact, the writer strongly favors the thesis that the course of evolution is usually so deliberate that there has resulted very slight specific change since mid-Pleistocene time. Any mammals then flourishing that were markedly different from those we know did not constitute the direct ancestors of the latter, but rather were they separate twigs of the parent branch, and they suffered extermination. There has been subspecific change, of course, but even this has probably been very slow for the most part. Races varying in their inherent plasticity naturally differ in their rate of change. Under violent and swift alteration of climate, which has probably been extremely infrequent, subspecies of the more plastic vertebrates may evolve in a few dozen or score of years, while more unyielding stock may resist slight changes of climate through scores of thousands of years. Needless to say, the facts on which we may base ideas as to previous climates are always meager, with some of them seemingly contradictory in character, and little of a positive nature may be claimed except that at indeterminate intervals there have been a number of climatic fluctuations on the Pacific Coast. Some times it was warmer, and at others cooler, than at present. In the past, as now, temperature and humidity were doubtless the two most important factors determining the distribution of life. Of vertebrated
Publication Year: 1927
Publication Date: 1927-01-01
Language: en
Type: article
Indexed In: ['crossref']
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