Dan McShea, Professor
Ph.D., University of Chicago, 1990
A.B., Harvard College, 1978
Organismal Biology and Behavior
Research Categories: Pyschobiology, Macroevolution, Philosophy of Biology
Current projects: 1) Theory of feeling and motivation, 2) Theory of the evolution of complexity
Research Description: My main research interest is hierarchy theory, especially the causal relationship between higher-level wholes and their components (Spencer, Simon, Campbell, Salthe, Wimsatt). In biology, for example, we might want to know how large scale processes within a multicellular organism act to control the smaller-scale processes within its component cells. Or, in the area of my current research, how do the emotions in mammals (and perhaps other animals) act to initiate and control conscious thought and behavior? It seems clear from the philosophical work of Hume (A Treatise of Human Nature) that the preferencing or valuing that motivates or drives conscious thought and behavior, and in particular conscious decision-making, must arise from the emotions. This is true because the only alternative, reason (in the sense of pure rationality), is value-neutral, and utterly incapable of motivating anything. As Hume put it, "Reason is and ought to be the slave of the passions and can never pretend to any other office than to serve and obey them."
But what is the nature of the causal process by which emotion drives thought and behavior? I argue that it is a form of downward causation, of a sort that occurs in many hierarchical systems. Consider a balloon filled with gas. If the balloon as a whole is moved -- say 2 inches to the left -- this large-scale movement causes all of the gas molecules within it (as well as the molecules in the plastic skin of the balloon) to move, on average, 2 inches to the left. A similar sort of top-down causation occurs, it seems, in the emotion-behavior and emotion-thought relationship. The evidence is that these relationships seem to follow certain key principles of hierarchy theory. 1. Rates. Lower levels move quickly relative to the higher level. The gas molecules in a balloon typically move quickly relative to the balloon as a whole. Likewise, thought and behavior are fast relative to change in emotional state. 2. Causal asymmetry. Lower-level units cannot, as individuals, much affect the higher level. A single gas molecule cannot much affect a whole balloon. Likewise, individual thoughts and behaviors ordinarily do not much affect an emotion. Rather, an emotion hovers more or less unchanging, in the background, while thoughts and behaviors aimed at satisfying that emotion play out. 3. Vagueness. Lower-level units do not directly interact with higher levels and therefore "perceive" them only "vaguely." Thus, thoughts and behaviors are clear and distinct, but we perceive our emotions only vaguely. 4. Downward causation. Higher levels exert their causal influence on lower-level units via boundary conditions, and therefore higher-level control is not precise, with the result that lower-level units have considerable freedom. Consistent with this, in two similar higher-level systems, the sequence of behaviors of lower-level units could be very different. The movements of individual gas molecules in two very similar balloons will be very different. Likewise, the same emotion, the same motivation, in two different people is consistent with their thinking and behaving very differently. (Although presumably some very general similarities can be found. To the extent that the two share the same emotion, the goals they are pursuing are similar. Analogously, the movements of the gas molecules in the balloon share a general similarity, in that they all move two inches to the left on average.)
My past work has been mainly on large-scale evolutionary trends, that is, trends that include a number of higher taxa and that span a large portion of the history of life. Features that have been said to show such trends include complexity, size, fitness, and others. In my research, I worked mainly on developing operational measures of these features, devising methods for testing empirically whether trends have occurred, and studying the causes and correlates of trends. Most of this work so far has been on trends in complexity. In a recent book (Biology’s First Law, publication expected 2010) with the philosopher Robert Brandon, we argue that complexity change in evolution is partly governed by what we call the Zero-Force Evolutionary Law (ZFEL). The law says that in the absence of selection and constraint, complexity – in the sense of differentiation among parts – will tend to increase. Further, we argue, even when forces and constraints are present, a tendency for complexity to increase is always present. The rationale is simply that in the absence of selection or constraint, the parts of an organism will tend spontaneously to accumulate variation, and therefore to become more different from each other. Thus, for example, in a multicellular organism, in the absence of selection and constraint, the degree of differentiation among cells should increase, leading eventually to an increase in the number of cell types. As we argue in the book, the law applies at all hierarchical levels (molecules, organelles, cells, etc.). It also applies above the level of the organism, to differences among individuals in populations, and to differences among species and among higher taxa. In other words, the ZFEL says that diversity also tends spontaneously to increase. The ZFEL is universal, applying to all evolutionary lineages, at all times, in all places, everywhere life occurs. A consequence is that any complete evolutionary explanation for change in complexity or diversity will necessarily include the ZFEL as one component.
Other interests include the philosophy of biology generally. See a new textbook coauthored with philosopher Alex Rosenberg, Philosophy Of Biology: A Contemporary Introduction. Also: 1. The connections among the various evolutionary forces acting on animal form -- functional, formal, and phylogenetic. 2. Animal psychology generally. 3. The relationship between morality and human nature.
Areas of Interest:
philosophy of biology
- A. Rosenberg and D.W. McShea, Philosophy of Biology: A Contemporary Introduction (2007), Routledge. [abs].
- Payne, J.L., A.G. Boyer, J.H. Brown, S. Finnegan, M. Kowalewski, R.A. Krause, Jr., S.K. Lyons, C.R. McClain, D.W. McShea, P.M. Novack-Gottshall, F.A. Smith, J.A. Stempien, and S.C. Wang, Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity, Proceedings of the National Academy of Sciences, vol. 106 (2009), pp. 24-27 .
- J. Marcot and D.W. McShea, Increasing hierarchical complexity throughout the history of life: phylogenetic tests of trend mechanisms, Paleobiology, vol. 33 (2007), pp. 182-200 [abs] [author's comments].
- D.W. McShea, The evolution of complexity without natural selection (or, a possible large-scale trend of the fourth kind), Paleobiology, vol. 31 (Supplement) (2005), pp. 146-156 .
- D.W. McShea, A universal generative tendency toward increased organismal complexity, in Variation: A Central Concept in Biology, edited by B. Hallgrimsson and B. Hall (2005), pp. 435-453, Academic Press .
- D.W. McShea and C. Anderson, The remodularization of the organism, in Modularity: Understanding the Development and Evolution of Natural Complex Systems, edited by W. Callebaut and D. Rasskin-Gutman (2005), pp. 185-206, The MIT Press .
- L. Marino, D.W. McShea, and M.D. Uhen, Origin and evolution of large brains in toothed whales, Anatomical Record, vol. 281A (2004), pp. 1247-1255 .
- D.W. McShea and M.A. Changizi, Three puzzles in hierarchical evolution, Integrative and Comparative Biology, vol. 43 (2003), pp. 74-81 .
- D.W. McShea, A complexity drain on cells in the evolution of multicellularity, Evolution, vol. 56 no. 3 (2002), pp. 441-452 .
- D.W. McShea and E.P. Venit, Testing for bias in the evolution of coloniality: A demonstration in cyclostome bryozoans, Paleobiology, vol. 28 no. 3 (2002), pp. 308-327 .
- D.W. McShea, The "minor transitions" in hierarchial evolution and the question of directional bias, Journal of Evolutionary Biology, vol. 14 (2001), pp. 502-518 .
- D.W. McShea, The hierarchical structure of organisms: a scale and documentation of a trend in the maximum, Paleobiology, vol. 27 (2001), pp. 405-423 .
- Anderson, C and DW McShea, Individual versus social complexity, with particular reference to ant colonies, Biological Reviews (of the Cambridge Philosophical Society), vol. 76 (2001), pp. 211-237 .
- D.W. McShea and E.P. Venit, What is a part?, in The Character Concept in Evolutionary Biology, edited by G.P. Wagner (2001) .
- D.W. McShea, Functional complexity in organisms: parts as proxies, Biology and Philosophy, vol. 15 (2000), pp. 641-668 .
- D.W. McShea, Feelings as the proximate cause of behavior, in Where Psychology Meets Biology: Philosophical Essays, edited by V.G. Hardcastle (1999), Cambridge University Press .
- D.W. McShea, Possible largest-scale trends in organismal evolution: eight "live hypotheses", Annual Review of Ecology and Systematics, vol. 29 (1998), pp. 293-318 .
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