Thesis ID: CBB001560834

On the Germ-Soma Distinction in Evolutionary Biology: A Historical and Conceptual Approach (2006)


Yamashita, Grant Joo (Author)

University of California, Davis
Griesemer, James R.

Publication Date: 2006
Edition Details: Advisor: Griesemer, James R.
Physical Details: 166 pp.
Language: English

Despite the spate of historical, empirical, and theoretical work on germ cells, there is still much we do not know about the evolution of germ and soma. Indeed, there exist large lacunae in both empirical and conceptual work on the problem of how and why many multicellular organisms develop a distinct germ line separated from the somatic line. What is missing from the evolution of germ-soma debates is a conceptual framework for assessing the merits and pitfalls of various models and approaches. My project, which I view as "conceptualizing the germ," builds a preliminary conceptual framework for understanding the germ-soma distinction and involves approaches that analyze research in the history and philosophy of biology as well as in contemporary developmental and evolutionary biology. Chapter 1 addresses the idea that what germ cells are can sometimes be answered by looking at when germ cells are said to appear in development. Using Weismann and de Vries as historical examples, I argue that germ and soma definitions are dependent on commitments such as choice of research organism. In Chapter 2 I compare contemporary and historical definitions of the germ-plasm concept and trace its change in meaning and address its consequences to evolutionary biology. Specifically, I investigate the research of Robert Hegner and assess his role in the changing concept of the germ-plasm, as well as its effect on the germ-cell and germ-plasm continuity theories of the 20 th century. In Chapter 3 I review select models of germ-soma development in the literature. What do these various models tell us about germ-soma development? Are there any similarities in the various approaches? I suggest that the models show a bias toward "preformistic" organisms and also focus on the evolution of multicellularity. Extending the results from the review of the models, in Chapter 4 I argue against sentiment that the germ is a relic of the past and instead contend that the role of the germ in contemporary developmental and evolutionary context is in stabilizing and maintaining the evolutionary transition to multicellularity.


Description From the 19th century work of Weismann and de Vries to 20th century concepts of germ-cell and germ-plasm. Cited in Diss. Abstr. Int. A 68/02 (2007). Pub. no. AAT 3250876.

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Authors & Contributors
Martins, Lilian A.-C. Pereira
Morange, Michel
Reynolds, Andrew S.
Weismann, August
Archibald, J. David
Churchill, Frederick B.
History and Philosophy of the Life Sciences
Filosofia e História da Biologia
Historical Studies in the Physical and Biological Sciences
Journal of Biosciences
Journal of the History of Biology
Science and Education
Cambridge University Press
Belknap Press of Harvard University Press
Columbia University Press
EDP sciences
Cellular biology
Molecular biology
Weismann, August
Darwin, Charles Robert
Vries, Hugo Marie de
Galton, Francis
Spencer, Herbert
Ankel, Wulf Emmo
Time Periods
19th century
20th century
18th century
20th century, late
20th century, early
21st century
Naples (Italy)
Stazione Zoologica di Napoli
Kaiser-Wilhelm-Institut für Biologie, Berlin

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