Chapter 1, Section 2 - Integrative Biology

(Autumn, K. 1995. Chapter 1, Section 2. Integrative Biology. Ph.D. Dissertation, University of California at Berkeley)

Kellar Autumn
Museum of Vertebrate Zoology and Department of Integrative Biology
3101 Valley Life Sciences Building
University of California, Berkeley CA 94720-3160
email: gecko@garnet.berkeley.edu

INTEGRATIVE BIOLOGY

Reductionism and holism form one of the fundamental dichotomies in science in general and biology in particular (Reippel 1988). Reductionism has been the predominant paradigm in biology during the 20th century (Benson 1989) -as witnessed by the current trend to use molecular explanations for all aspects of life (Savageau 1991). It could be argued that science is fundamentally reductionist in its methodology, and that as biology progresses, its explanations must be on an increasingly small scale. On the contrary, I will argue that a truly progressive biology is not solely reductionist. Holism has been historically associated with metaphysics, and the eclipse of vitalism by (reductionist) materialism during the enlightenment (Benson 1989) has given holism a negative connotation in science. However when viewed in a modern context, holism need not be linked in any way to metaphysics (Ruse 1989). Holism is at the philosophical core of studies of complex, integrated systems such as living organisms (Wake et al. 1983; Wake and Larson 1987; Russert-Kraemer and Bock 1989; Pahl-Wostl 1993). The holistic approach to organismal biology has as its central tenet the assumption that a living organism is greater than the sum of its parts (Ruse 1989). This approach is integrative because it focuses on the interaction or integration of parts in a functioning organism. Integrative biology may use typically reductionist methods, but in a philosophically holistic framework. The difference between reductionist and integrative biology is not simply a philosophical distinction; the integrative approach to biology differs dramatically from reductionist biology in both its goals and its methods. While the goal of reductionist biology is to understand life in terms of simple deterministic principles analogous to Newtonian physics or chemistry (Savageau 1991), the goal of integrative biology is to understand the structure, function, and history of organisms and their environments. These are not mutually exclusive goals. Much of the progress made by reductionist biology can be applied to reach the more inclusive goal of integrative biology.

Because organisms and their environments form complex integrated systems, the most robust biology will be an integrative biology (Ruse 1989; Russert-Kraemer and Bock 1989; Savageau 1991). Organisms and their environments are studied (of necessity) on many hierarchical levels -for instance the focal unit of biological organization can be a gene, cell, organism, population, or species, depending on the focal level of study (Jacob 1977; Bock 1989). Scientific explanations rely on establishing causal relationships among units of study (Bock 1989). One the most fundamental methodological differences between reductionist and integrative biology is in models of causality. Reductionist biology has a much more restrictive model of causality than does integrative biology. The reductionist model is one of unidirectional causation (Fig. 1.1). Reductionism assumes that effects at higher levels of biological organization can always be reduced to causes at lower levels (Jacob 1977). For instance, the reductionist approach assumes that effects at organismal level can always be reduced to causes at the gene level. Models of causality in integrative biology are much more complex. The integrative model is one of multidirectional causality that traces causal threads within and between hierarchical levels, and through time. For instance, population dynamics and natural selection on individual organisms can determine which genes are replicated in future generations. In the integrative model, causality can occur from the highest levels to the lowest: temperature dependent sex determination is an example of how the environment can affect gene expression (Ewert et al. 1994; Lang and Andrews 1994; Viets et al. 1994). Only one of many possible directions of causation is from gene to organism. In this sense, integrative biology encompasses the methods of reductionist biology but goes much farther. Reductionist biology has made tremendous advances in the "parts catalog" (Savageau 1991) of life. However, the reductionist approach has failed to make significant progress in the study of complex systems (Savageau 1991). This is primarily because system dynamics often cannot be reduced to a linear causal model. It is time to move beyond reductionism to expand the understanding of how parts fit together to form functioning, evolving organisms.