Mammals and land bridges
Journal of the Washington Academy of Sciences, (1940)Abstract
When I undertook to discuss this subject, it was my first intention to take up the various theoretical land bridges from one continent to another and to summarize the evidence for and against each one in order to produce a historical account of where and when such bridges have existed. It soon became apparent that such an account, if it were to have any value, would involve a mass of detail that would, indeed, be of interest only to specialists in this field. It also became evident that relatively few such specialists have risen above this mass of detail to make a conscious survey of the general principles involved and of the basic assumptions underlying their studies. Such a general survey is, then, not only of wider interest but also fresher and more needed in the present stage of study.
To review all the broad problems and principles in one paper is a manifest impossibility, and attention will be directed to two aspects on which it now seems possible and useful to make some suggestions. The first is the broadest problem of all in this field, the general way in which land mammals tend to become distributed and in which their distribution tends to change in time. The second is more particular: the different types of migration routes between major land areas, the way in which one type or another can be inferred from the faunal evidence, and the effect that a given type has on the faunas that use it. In order to lend reality to these abstractions and to point out some further promising leads for research, one specific example of
the rise of a migration route between continents is then taken and what happened to the continental faunas as a consequence is briefly considered.
Description
Written before plate tectonics.