CNCS Center for Nonlinear and Complex Systems
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Daniel W. McShea, Professor of Biology

Daniel W. McShea

Please note: Daniel has left the "CNCS: Center for nonlinear and complex systems" group at Duke University; some info here might not be up to date.

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 neutrally buoyant balloon filled with gas and hanging in a room. 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 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 my textbook coauthored with philosopher Alex Rosenberg, Philosophy Of Biology: A Contemporary Introduction 2009.) More specifically: 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.

Contact Info:
Office Location:  139 Bio Sci Bldg, Durham, NC 27708
Office Phone:  (919) 225-8679
Email Address: send me a message
Web Page:

Teaching (Fall 2023):

  • BIOLOGY 516S.01, LIFE'S PURPOSE Synopsis
    Bio Sci 155, TuTh 10:05 AM-11:20 AM
    (also cross-listed as PHIL 516S.01)
    Bio Sci 063, Tu 12:00 PM-02:30 PM

Ph.D.The University of Chicago1990
M.S.The University of Chicago1987
B.A. Harvard University1978
A.B.Harvard College1978

Organismal Biology and Behavior
Philosophy of Biology
Cognitive Science
Research Interests: Macroevolution, paleobiology, philosophy of biology

Current projects: 1)Theory of the evolution of complexity, 2) Theory of feeling and motivation

I am interested in large-scale evolutionary trends, that is, trends that include a number of higher taxa and 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 have been developing operational measures of these features, devising methods for testing empirically whether trends have occurred, and studying the causes and correlates of trends. My major work so far has been on trends in complexity. I am also interested in: 1. The relationships among the various evolutionary forces acting on animal form -- functional, formal, and phylogenetic. 2. Theoretical aspects of animal psychology. 3. The philosophy of biology.

Areas of Interest:

evolution of complexity
proximate mechanisms of behavior/animal psychology
philosophy of biology


Adaptation, Biological • Aerobiosis • Anaerobiosis • Animals • Ants • Artificial Intelligence • Atmosphere • Behavior, Animal • Biological Evolution • Body Size • Brain • Cell Physiological Phenomena • Cetacea • Classification • complexity • Computer Simulation • Cyanobacteria • Developmental Biology • Drosophila melanogaster • Earth (Planet) • Entropy • Environment • Eukaryotic Cells • evolution • Evolution • Evolution, Molecular • Fossils • Gene Expression Regulation, Developmental • Genetic Fitness • Genetic Variation • Geologic Sediments • Geological Phenomena • Geology • Goals • hierarchy • History, 20th Century • History, 21st Century • History, Ancient • Humans • Insects • Logic • Macroevolution • Mammals • Mathematics • Metazoa • Models, Biological • Motivation • Muser Mentor • Mutation • Oxygen • Paleontology • Personal Satisfaction • Philosophy • Philosophy of Biology • Photosynthesis • Pigmentation • Plant Development • Rabbits • Rats • Science • Selection, Genetic • Social Behavior • Teleology • Time Factors • Tomography, Spiral Computed • Tooth • Trees • Wing • Zoology

Current Ph.D. Students   (Former Students)

    Representative Publications   (More Publications)

    1. McShea, DW, Upper-directed systems: A new approach to teleology in biology, Biology & Philosophy, vol. 27 no. 5 (September, 2012), pp. 663-684, Springer Nature, ISSN 0169-3867 [doi]  [abs]
    2. D.W. McShea and Robert Brandon, Biology's First Law (2010), University of Chicago Press
    3. Fleming, L; McShea, DW, Drosophila mutants suggest a strong drive toward complexity in evolution, Evolution and Development, vol. 15 no. 1 (2012), pp. 53-62 (Paper was written up in a Scientific American piece by Carl Zimmer. Attached.) [23331917], [doi]  [abs]
    4. Marcot, JD; McShea, DW, Increasing hierarchical complexity throughout the history of life: Phylogenetic tests of trend mechanisms, Paleobiology, vol. 33 no. 2 (March, 2007), pp. 182-200, Cambridge University Press (CUP), ISSN 0094-8373 [doi]  [abs] [author's comments]
    5. McShea, DW; Hordijk, W, Complexity by Subtraction, Evolutionary Biology, vol. 40 no. 4 (December, 2013), pp. 504-520, ISSN 0071-3260 [doi]  [abs]
    6. McShea, DW, The evolution of complexity without natural selection, a possible large-scale trend of the fourth kind, Paleobiology, vol. 31 no. 2 SUPPL. (July, 2005), pp. 146-156, Cambridge University Press (CUP) [doi]  [abs]
    7. McShea, DW, Machine wanting., Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences, vol. 44 no. 4 Pt B (December, 2013), pp. 679-687, ISSN 1369-8486 [23792091], [doi]  [abs]
    8. McShea, DW, A universal generative tendency toward increased organismal complexity, in Variation: A Central Concept in Biology, edited by B. Hallgrimsson and B. Hall (December, 2005), pp. 435-453, Elsevier [doi]  [abs]
    9. 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
    10. Marino, L; McShea, DW; Uhen, MD, Origin and evolution of large brains in toothed whales., The Anatomical Record. Part A, Discoveries in Molecular, Cellular, and Evolutionary Biology, vol. 281 no. 2 (December, 2004), pp. 1247-1255, ISSN 1552-4884 [15497142], [doi]  [abs]
    11. McShea, DW; Changizi, MA, Three puzzles in hierarchical evolution., Integrative and Comparative Biology, vol. 43 no. 1 (February, 2003), pp. 74-81, ISSN 1540-7063 [21680411], [doi]  [abs]
    12. McShea, DW, A complexity drain on cells in the evolution of multicellularity., Evolution; International Journal of Organic Evolution, vol. 56 no. 3 (March, 2002), pp. 441-452, ISSN 0014-3820 [11989676], [doi]  [abs]
    13. McShea, DW; Venit, EP, Testing for bias in the evolution of coloniality: A demonstration in cyclostome bryozoans, Paleobiology, vol. 28 no. 3 (Summer, 2002), pp. 308-327, Cambridge University Press (CUP) [doi]  [abs]
    14. McShea, DW, The minor transitions in hierarchical evolution and the question of a directional bias, Journal of Evolutionary Biology, vol. 14 no. 3 (July, 2001), pp. 502-518, WILEY, ISSN 1010-061X [doi]  [abs]
    15. McShea, DW, The hierarchical structure of organisms: A scale and documentation of a trend in the maximum, Paleobiology, vol. 27 no. 2 (January, 2001), pp. 405-423, Cambridge University Press (CUP) [doi]  [abs]
    16. Anderson, C; McShea, DW, Individual versus social complexity, with particular reference to ant colonies., Biological Reviews of the Cambridge Philosophical Society, vol. 76 no. 2 (May, 2001), pp. 211-237, ISSN 1464-7931 [11396847], [doi]  [abs]
    17. McShea, DW; Venit, EP, What is a Part?, in The Character Concept in Evolutionary Biology, edited by G.P. Wagner (2001), pp. 259-284, Elsevier, ISBN 9780127300559 [doi]
    18. McShea, DW, Functional complexity in organisms: Parts as proxies, Biology & Philosophy, vol. 15 no. 5 (December, 2000), pp. 641-668, Springer Nature, ISSN 0169-3867 [doi]  [abs]
    19. 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
    20. McShea, DW, Possible largest-scale trends in organismal evolution: Eight 'live hypotheses', Annual Review of Ecology and Systematics, vol. 29 no. 1 (December, 1998), pp. 293-318, ANNUAL REVIEWS [doi]  [abs]