content： Although it is quite conceivable that behavioral propensities yield more readily to selection pressures and are, perhaps, also more easily affected by genetically conditioned variations, thus changing at a more rapid rate than skeletal structure, for instance, we must still remember that all evolutionary changes affect animals as a whole. Entire patterns of life, so to speak, are altered but at each time-slice there is, necessarily, full integration and mutually adaptive interaction of all of the animal’s features; it is the condition for viability and successful continuation of the species. This consideration has an important consequence for reasonable expectations of the phylogenetic history of one specific trait, such as human language. Individual traits of an extant species can never have a continuous history because they do not evolve independently from the rest of the animal. Thus we see that there is every reason to believe that animal communication is a discontinuous affair and that logical commonalities among communication systems are not necessarily indicators of a common biological origin. FIG. 6.3. Schema of the evolution of the Hominoidea. (c) The Sharing of Traits. These assertions are not contradicted by the wealth of evidence that some sort of symbolic behavior can be demonstrated in a wide variety of animals, that the communication of affect is very common, or that territoriality, protection of the young, or maternal behavior is frequently accompanied by vocalizations. It is true that animals share certain traits; it follows directly from the tree-like relationship between species. Notice, however, that the phylogenetic relationship between species cannot, in most cases, be represented by a single, unique tree-diagram that accounts for absolutely all of the commonalities and all of the specific differences. A tree that characterizes the relationship of skeletal structures of certain species fairly well, may differ in some (usually small) respect from a tree that characterizes the relationship between given protein structures (Goodman, 1963).
FIG. 6.4. Tree diagrams or descent may be represented as Euler-Venn diagrams.
(a) is a representation of Fig. 6.3 (Chapter Six). Individual traits of behavior are often distributed over species in such a complex way that tree diagrams cannot be used at all, and set diagrams can only be used at the risk of oversimplification.
(b) is a hypothetical representation of vertebrate communication systems that could not be shown by a single tree.
This is due to a number of circumstances; for example, certain aspects of life do not allow of as many (or any) variations as others; or there may be only one or very few possible biochemical solutions to a given problem posed by the environment so that a similar condition comes about more than once throughout the animal kingdom; or certain features are lost or added by individual species.
Tree-diagrams may be converted to Euler-Venn diagrams such as shown in Fig. 6.4 where (a) is a representation of the tree in Fig. 6.3 and (b) is a hypothetical diagram that might show some of the relationships of individual traits, some of them pertinent to human language. Each of the rings may be labelled; the labels tend to become more abstract as we move from center to periphery. The inner circles represent phenomena that can be directly observed on present-day animals. Each encompassing ring is a postulation lf a more general form of the contemporary phenomenon. If an outer ring be vocalizations, this will not be a homogeneous set of behaviors but a collection of types of behavior each of which is today a highly specialized biological function. Thus we see once more that the sharing of traits does not necessarily reveal the history or nature of any specific development.
Ⅱ. ARE BIOLOGICAL THEORIES OF LANGUAGE DEVELOPMENT COMPATIBLE WITH CONCEPTS OF GENETICS?
Before we proceed with further speculations about the biological origins of language, we must pause to ask whether present-day concepts of genetics and development are compatible with the facts known about language.
(1) Genes and Ontogenetic Development
The first problem is posed by what is known about the specific action of genes. DNA molecules, the biochemical correlates of genes. Probably do no more than control the protein synthesis within the cell. The undifferentiated cells of higher animals have, however, a very large repertoire of different “instructions” for different types of synthesis, and these come into play at various stages of development (Beermann, 1963). The puzzle now is: if the inherited genetic information concerns essentially nothing but intracellular events, how could something like the capacity for language have a genetic foundation? The phenomenon is, after all, entirely supracellular or even more general, namely an interrelation of activities of complex assemblies of cells.
This puzzle is, of course, not peculiar to the problems of the genetic basis of language but to the relationship between genic action and the inheritance of traits in general. Although we can only speculate on this point, our speculations with regard to language are no more daring than with regard to most other structural or functional features.
Animals develop as an integrated whole including structure, function and behavioral capacities; the latter two are not secondary installations after embryogenesis. Therefore, it may not be too far-fetched if we say a word about development in general, the assumed role of genes in ontogenetic and phylogenetic development, and how these concepts apply to the development of language.
It is common knowledge that the first cells formed during mammalian ontogenesis have embryological equipotentiality. Up to the stage called gastrulation, the cell aggregate may be divided artificially in two, and each remaining half will develop into a well-shaped individual. But soon some of the cells in the gastrula become specialized, a division of labor has set in among the cells which soon deprives them of the capacity to change their own structure and function back to the original state. A certain spot in the gastrula begins to act on surrounding cells, thus inducing fast cell division, local expansion, folding, invagination, tubular structures, inclusions, etc. We speak of an organizer that has developed and which has caused some differentiation in its neighborhood. Organizer after organizer develops. At later stages entire tissues or organs serve as organizers or inducers for other tissues and organs.
來源 : http://cell.lifescience.ntu.edu.tw/old_version/academic/
How my tool helped me to solve problems? 我使用的工具是網路上的字典搜尋引擎，用來查詢我不懂的單字，例如phylogenetic和gastrulation是比較學術的專有名詞，透過此工具查詢讓我能繼續閱讀下去。