Theories and explanations in biology

Conclusion It seems that the above account of explanation-strategy in the area of temperature adaptation underscores many of the points made earlier. First, it discloses the fruitful interaction of classical, evolutionary, and molecular approaches. Secondly, it indicates that biological characterizations are not rival accounts to chemical ones. Thirdly, it stresses the importance of the DNA sequence order in chemical explanations of biological organisms.One feature which this area does not seem to reveal, which genetics does, is the development of a biological (that is, non-chemical) theory which would explain temperature adaptation in nonchemical terms. What this shows is that one should not always expect systematization at the biological level, in the sense of being able to refer many phenomena to a small number of basic principles. The future development of laws and theories in biological terms in this area is, of course, not precluded by the fact that none have yet been discovered. The case does indicate that physical and chemical language and theories are extremely useful in biological investigations, and the physicochemical approach may well be the best approach in this area. In any event, ultimate reduction of the biological to the chemical seems to be a foregone non-controversial conclusion here as elsewhere.     

Theories of ageing

Ageing is a universal, intrinsic, progressive and deleterious process. Understanding it is of major interest to scientist, physicians as well as to the general population. Critical to this understanding is to formulate comprehensive theories of aging with high predictive and explanatory power. More than 300 theories have been postulated and are reviewed here. The free radical theory of ageing is one of the most prominent and well studied. It was further developed by one of us (JM) in what has become known as the mitochondrial theory of ageing. These theories provide new experimental approaches to further develop our understanding of the phenomenon of ageing.     

Parts and Theories in Compositional Biology

I analyze the importance of parts in the style of biological theorizing that I call compositional biology. I do this by investigating various aspects, including partitioning frames and explanatory accounts, of the theoretical perspectives that fall under and are guided by compositional biology. I ground this general examination in a comparative analysis of three different disciplines with their associated compositional theoretical perspectives: comparative morphology, functional morphology, and developmental biology. I glean data for this analysis from canonical textbooks and defend the use of such texts for the philosophy of science. I end with a discussion of the importance of recognizing formal and compositional biology as two genuinely different ways of doing biology – the differences arising more from their distinct methodologies than from scientific discipline included or natural domain studied. Ultimately, developing a translation manual between the two styles would be desirable as they currently are, at times, in conflict.     

Theories of Culture in Postmodern Times

Theories of Culture in Postmodern Times. Marvin Harris. Walnut Creek. CA. London, and New Delhi: Altamira Press. 1999.224 pp.     

Theories and Major Hypotheses in Ethnobotany

Ethnobotany has evolved from a discipline that largely documented the diversity of plant use by local people to one focused on understanding how and why people select plants for a wide range of uses. This progress has been in response to a repeated call for theory-inspired and hypothesis-driven research to improve the rigor of the discipline. Despite improvements, recent ethnobotanical research has overemphasized the use of quantitative ethnobotany indices and statistical methods borrowed from ecology, yet underemphasized the development and integration of a strong theoretical foundation. To advance the field of ethnobotany as a hypothesis-driven, theoretically inspired discipline, it is important to first synthesize the existing theoretical lines of research. We review and discuss 17 major theories and hypotheses in ethnobotany that can be used as a starting point for developing research questions that advance our understanding of people–plant interactions. For each theory or major hypothesis, we identify its primary predictions and testable hypotheses and then discuss how these predictions have been tested. Developing research to test these predictions will make significant contributions to the field of ethnobotany and create the critical mass of primary literature necessary to develop meta-analyses and to advance new theories in ethnobotany.     

Theories of sexual selection

Recent research on sexual selection in animals has begun to indicate that 'handicaps' and 'honest signalling' may play more important roles than hitherto thought. This review reappraises theories of sexual selection in the light of these new developments.     

Theories of episodic memory

Theories of episodic memory need to specify the encoding (representing), storage, and retrieval processes that underlie this form of memory and indicate the brain regions that mediate these processes and how they do so. Representation and re-representation (retrieval) of the spatiotemporally linked series of scenes, which constitute an episode, are probably mediated primarily by those parts of the posterior neocortex that process perceptual and semantic information. However, some role of the frontal neocortex and medial temporal lobes in representing aspects of context and high-level visual object information at encoding and retrieval cannot currently be excluded. Nevertheless, it is widely believed that the frontal neocortex is mainly involved in coordinating episodic encoding and retrieval and that the medial temporal lobes store aspects of episodic information. Establishing where storage is located is very difficult and disagreement remains about the role of the posterior neocortex in episodic memory storage. One view is that this region stores all aspects of episodic memory ab initio for as long as memory lasts. This is compatible with evidence that the amygdala, basal forebrain, and midbrain modulate neocortical storage. Another view is that the posterior neocortex only gradually develops the ability to store some aspects of episodic information as a function of rehearsal over time and that this information is initially stored by the medial temporal lobes. A third view is that the posterior neocortex never stores these aspects of episodic information because the medial temporal lobes store them for as long as memory lasts in an increasingly redundant fashion. The last two views both postulate that the medial temporal lobes initially store contextual markers that serve to cohere featural information stored in the neocortex. Lesion and functional neuroimaging evidence still does not clearly distinguish between these views. Whether the feeling that an episodic memory is familiar depends on retrieving an association between a retrieved episode and this feeling, or by an attribution triggered by a priming process, is unclear. Evidence about whether the hippocampus and medial temporal lobe cortices play different roles in episodic memory is conflicting. Identifying similarities and differences between episodic memory and both semantic memory and priming will require careful componential analysis of episodic memory.     

Theories of Life-History Evolution

In order to assess current scientific understanding of life-historyevolution, the alternative fundamental theories are formulatedin a refutable form and compared with the available empiricalevidence. The hypothesis that life-history does not evolve isrejected on the grounds that life-history can be readily modifiedby artifical selection. The hypothesis that life-history evolvesaccording to mechanisms other than natural selection actingon genetic variation is shown to have no sound experimentalbasis. The hypothesis that life-history evolution depends primarilyon group selection is undermined by the absence of the predictedgroup adaptations. The hypothesis that life-history is a unitarycharacter which evolves in the same fashion as fitness is rejectedbecause of the disparity between life-history genetics and basictheory concerning the evolution of fitness. The hypothesis thatlife-history is composed of a set of autonomous characters whichare subject to mutation accumulation at later ages is refutedby the lack of any detectable increase in genetic variabilitywith age and the evidence for the interdependence of life-historycharacters. It is concluded that the hypothesis of antagonisticinteractions between life-history characters, generalized totake genetic variability into account, is the most satisfactorytheory of life-history evolution available.     

Theories of Social Honor

The approaches used in studying status systems (or systems of prestige or social honor) can be classified as either materialist or nonmaterialist, and the essential differences between them reflect differences in assumptions about human motivations. It is argued that the materialist approach is untenable. The nonmaterialist approaches also differ among themselves in motivational assumptions, and these differences in turn lead to very different views about the nature of status systems. Three nonmaterialist approaches are analyzed, and it is suggested that one of them is more compelling than the others.