The tree, of course, is a particularly powerful symbol in Western culture and figures prominently in many of our myths and metaphors, so it is not surprising that it has come to occupy a central place in the study of language. The tree is, after all, a symbol of strength and renewable life, but above all it is a double-edged symbol of the sometimes arrogant, sometimes noble human quest for knowledge and wisdom. It is no accident that our central metaphor for scientific discovery is a falling apple striking Newton on the head, the fruit of the tree thereby imparting to him fundamental knowledge of the workings of the universe. A central theme of this book is that there are other, perhaps better, images than trees to picture the structures of individual languages and the structures of interrelationship among all languages. Darwin's image of the "tangled bank" may be more apropos:
It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling in the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.
Though Darwin's views were sometimes ridiculed by his contemporaries (see fig. 3), his image provides a vehicle for viewing language as a complex of sequential, hierarchical processes, as well as processes that are more simultaneous and overlapping. It will also be argued that the interrelationships among the words or signs of a single language and the relationships among languages that contact one another are similarly complex and cannot be accounted for by the neatly branching trees of the linguist or logician.
Two very significant traditions in Western thought have had a profound impact on the development of linguistic theory. These traditions are descended from Plato and Descartes, respectively. In the Platonic scheme of the world, the ordinary manifestations of phenomena such as languages are thought of as pale and imperfect reflections of ideal forms, while the Cartesian program supports the notion of a mind-body dualism, in which the mind is governed by laws and forces other than those that govern the functions of the body. Throughout this book we will encounter treatments of language in which it is assumed that actual speech in a particular language is always an imperfect expression of a rigid, rule-based system, and that fundamental rules govern all languages. These latter rules, in turn, are said to be independent of other aspects of the cognitive or physiological functioning of human organisms. The Platonic and Cartesian tendencies in linguistics have thus led to the position that there are no significant differences among languages, other than surface variations in lexicon and syntax. This notion will be explored more fully herein, but it is worth noting that this was a progressive idea intended to counteract the racism and ethnocentrism of Western society. It may, however, have gone too far. This book takes seriously an older anthropological linguistics, propounded by the likes of Edward Sapir and Benjamin Lee Whorf, that asserted the worth of each language but that also considered each language as a natural experiment intimately connected to the culture of the people who spoke it.
An additional caveat is in order here. Few scholarly questions are more bound up in human politics than the major questions to be addressed in this book. The issues involved are central to questions as fundamental as those surrounding the causes of the inequalities among current human populations. Increasing understanding is, therefore, dependent upon disentangling scientific and scholarly arguments from political ones—"deconstructing" these arguments, to use jargon that is current in some social science circles. In this regard, the author takes the dominant position resulting from the preponderance of anthropological research during the twentieth century—that no important behavioral differences among modern human populations can be ascribed to differences in gene frequencies. Besides being morally reprehensible, racist explanations of interpopulation differences in such things as social and technological complexity are also scientifically untenable. But this is emphatically not to say that no important differences among individuals are genetically based, nor is it to say that no important behavioral differences exist among human groups. Rather, the latter are better explained in terms of differences in ideology, in access to natural resources, or even in language than in characteristics of their gene pools.