Human evolution theory utilizing concepts of neoteny & female sexual selection
An etiology of neuropsychological disorders such as autism and dyslexia, and the origin of left handedness.

twitter / andrewL9

Gilbert Gottlieb

Individual Development & Evolution: Bibliographical Excerpts

"The entire scheme represents a hierarchically organized system of increasing size, differentiation, and complexity, in which each component affects, and is affected by, all the other components, not only at its own level but at lower and higher levels as well. Thus, the arrows in Figure12-2 not only go upward from the gene, eventually reaching all the way to the external environment through the activities of the organism, but the arrows of influence return from the external environment through various levels of the organism back to the genes. While the feedforward or feedupward nature of the genes has always been appreciated from the time of Weismann and Mendel on, the feedbackward or feeddownward influences have usually been thought to stop at the level of the cell membrane. The newer conception is one of a totally interrelated, fully coactional system in which the activity of the genes themselves can be affected through the cytoplasm of the cell by events originating at any other level in the system, including the external environment." (Gilbert, G (1992) Individual Development & Evolution. Oxford Univ. Press: New York p. 145)

" 'As I have already pointed out, there is an interesting problem concerning the possible interaction between the chromatin of the cells and the protoplasm during development. The visible differentiation of the embryonic cells takes place in the protoplasm. The most common genetic assumption is that the genes remain the same throughout this time. It is, however, conceivable that the genes also are building up more and more, or are changing in some way, as development proceeds in response to that part of the protoplasm in which they come to lie, and that these changes have a reciprocal influence on the protoplasm. It may be objected that this view is incompatible with the evidence that by changing the location of cells, as in grafting experiments and in regeneration, the cells may come to differentiate in another direction. But the objection is not so serious as it may appear if the basic constitution of the gene remains always the same, the postulated additions or changes in the genes being of the same order as those that take place in the protoplasm. If the latter can change its differentiation in a new environment without losing its fundamental properties, why may not the genes also? This question is clearly beyond the range of present evidence, but as a possibility it need not be rejected. The answer, for or against such an assumption, will have to wait until evidence can be obtained from experimental investigation. (Morgan, 1934, p. 234)' What Morgan is proposing here, in the final paragraph of his 1934 book, is that the integration of genetics with development could be achieved only when the gene is actively incorporated into the developmental process and that its activity is seen as reciprocally altered thereby (i.e., not only feedforward effects {gene [arrow right] protein} but feedback effects as well {gene [arrow left] protein}). To those who viewed (and view) the integrity of the gene as absolutely constant, operating essentially outside the reciprocally interactive developmental system, the notion that "genes are changing in some way" was, and is, indeed a radical suggestion. But if there is to be a truly developmental genetics, genes will have to be viewed in some sense as Morgan suggested (and as the geneticist Sewall Wright suggested) and thus become part of the entire system of mutual interactions that is the hallmark of embryological analysis and that characterizes the epigenetic development of the individual." (Gilbert, G (1992) Individual Development & Evolution. Oxford Univ. Press: New York p. 138-9)



Related Links