Chapter 1
Introduction

This introductory chapter begins with an explanation of why the study of the history of a subject is important, and highlights some of the significant lessons that students may gain from it. This is followed by a review of the way in which each of the areas of research in biogeography developed from its foundation to today.

Lessons from the Past

Before starting to outline the structure of biogeography today, it is worthwhile to try to explain how scientists work, and what their limitations are - how far should the student trust what they say and believe? And the best way to learn this is to look at how scientists have behaved in the past, for the research workers of today are no different from them. So history has much to teach us

It is natural to assume that any research worker is free to make any sort of suggestion as to what new idea they might put forward in trying to solve their current problems - but the reality is rather different. Just as in the past, the range of what are seen as possible solutions is limited by what contemporary society or science views as permissible or respectable. Attitudes to the idea of evolution (Chapter 6) or of continental drift (see later in this chapter) are good examples of such inhibitions in the 19th and 20th centuries, and the concept of evolution is still controversial today in some societies and communities. The history of scientific debate is rarely, if ever, one of dispassionate, unemotional evaluation of new ideas, particularly if they conflict with one's own. Scientists, like all men and women, are the product of their upbringing and experience, affected by their political and religious beliefs (or disbeliefs), by their position in society, by their own previous judgements and publicly expressed opinions, and by their ambitions - just as 'There's no business like show business', there's no interest like self-interest! Very good examples of this, discussed later in this chapter, is the use of the concept of evolution by the rising middle-class scientists of England as a weapon against the 19th-century establishment while, at the individual level, the history of Leon Croizat and his ideas provides an interesting study.

In looking at the past, we shall therefore see people who, like most of us, grew up accepting the intellectual and religious ideas current in their time, but who also had the curiosity to ask questions of the world of nature around them. Sometimes the only answers that they could find contradicted or challenged the current ideas, and it was only natural then to seek ways to circumvent the problem. Could these ideas be reinterpreted to avoid the problem, was there any way, any loophole, to avoid a complete and direct challenge and rejection of what everyone else seemed to accept? So, to begin with, the reactions of any scientist confronted with results or ideas that conflict with what is currently accepted is either to reject them ('Something must have gone wrong with his methods, or with my methods') or to view them as an exception ('Well, that's interesting, but it's not mainstream'). Sometimes, however, these difficulties and 'exceptions' start to become too numerous, too varied or to arise from so many different parts of science as to suggest that something must be wrong. The scientist may then realize that the only way around it is to start again, starting from a completely different set of assumptions, and to see where that leads. Such a course is not easy, for it involves the tearing-up of everything that one has previously assumed, and completely reworking the data. And, of course, the older you get, the more difficult it is to do so, for you have spent a longer time using the older ideas and publishing research that explicitly or implicitly accepts them. That is why, all too often, older workers take the lead in rejecting new ideas, for they see them as attacking their own status as senior, respected figures. Sometimes these workers also refuse to accept and to use new approaches long after these have been thoroughly validated and widely used by their younger colleagues (see attitudes to plate tectonic theory, Chapter 5).

Another problem is that the debate can become polarized, with the supporters of two contrasting ideas being concerned merely to try to prove that the opponents' ideas are false, badly constructed and untrue (see dispersal vs. vicariance, discussed later in this chapter, and punctuated vs. gradual evolution, discussed in Chapter 6). Neither side then stops to consider whether it is perhaps possible that both of the apparently conflicting ideas are true, and that the debate should instead be about when, under what circumstances and to what extent one idea is valid, and when the other is instead the more important. Also, only too often, scientists have rejected the suggestions of another worker, not because they were in themselves unacceptable, but because they rejected other opinions of that same author (e.g. Cuvier vs. Lamarck on evolution, later in this chapter).

It is often valuable to think about why and when a particular advance was made. Was it the result of personal courage in confronting the current orthodoxy of religion or science? Was it the result of the mere accumulation of data, or was it allowed by the development of new techniques in the field of research, or in a neighbouring field, or by a new intellectual permissiveness? But the study of history also gives us the opportunity to learn other lessons - and the first of these is humility. We must be wary, when considering the ideas of earlier workers, not to fall into the trap of arrogantly dismissing those workers as in some way inferior to ourselves, simply because they did not perceive the 'truths' that we now see so clearly. In studying their ideas and suggestions, one soon realizes that their intellect was no less penetrating than those that we can see at work today. However, compared to the scientists of today, they were handicapped by lack of knowledge, for less was known and understood. For example, the French zoologist Lamarck suggested in 1809 that the long neck of a giraffe was the result of its ancestors having stretched their necks in order to reach high vegetation, and that this change had been inherited by their descendants - a theory known as the 'inheritance of acquired characteristics'. We now know that this is incorrect, and that it is instead the result of natural selection of those individuals who had longer necks. But Lamarck's theory was perfectly reasonable in the days before the recognition, early in the 20th century, of the work of Mendel in the mid-19th century, and the discovery of DNA in 1953.

So, when Isaac Newton, who originated the theory of gravitational attraction, wrote that he had 'stood on the shoulders of giants', he was acknowledging that in his own work he was building upon that of generations of earlier thinkers, and was taking their ideas and perceptions as the foundations of his own. So, the further we go back in time, the more we see intellects that had to start afresh, with a page that was either blank or contained little in the way of earlier ideas or syntheses.

All of this is particularly true of biogeography, for it provides the additional difficulty of being placed at the meeting point of two quite different parts of science - biological sciences and earth sciences. This has had two interesting results. The first is that, from time to time, lack of progress in one area has held back the other. For example, the assumption of stable, unchanging geography made it impossible to explain the fact that some organisms were found scattered across different continents, particularly in the Southern Hemisphere (see the distribution of the Glossopteris flora, later in this chapter). Nevertheless, it was a reasonable assumption until, much later, the acceptance of plate tectonics (continental drift) provided a vista of past geographies that had gradually changed through time. But it is also interesting to note that this major change in the basic approaches of earth sciences came in two stages.

To begin with, the problem was clearly posed and a possible solution was given. This was in 1912, when the German meteorologist Alfred Wegener (see later in this chapter) pointed out that many patterns in both geological and biological phenomena did not conform to modern geography, but that these difficulties disappeared if it was assumed that the continents had once lain adjacent to one another and had gradually separated by a process that he called continental drift. This explanation did not convince the majority of workers in either field of work, largely because of the lack of any known mechanism that could cause continents to move horizontally or to fragment. The fact that Wegener himself was not a geologist but an atmosphere physicist did not help him to persuade others of the plausibility of his views, for it was only too easy for geologists (who, of course, 'knew best') to dismiss him as a meddling amateur. Most biologists, faced with the uncertainties of the fossil record, did not care to take on the assembled geologists.

The second stage came only in the 1960s, when geological data from the structure of the sea floor and from the magnetized particles found in rocks (see Chapter 5) not only provided unequivocal evidence for continental movements, but also suggested a mechanism for them. Only then did geologists accept this...