International Society for History, Philosophy, and Social Studies of Biology

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WEDNESDAY, JULY 8  /  15:30 - 17:00  /  DS-M240
Individual papers
Evolutionary Explanations: Tree diagrams, Evo-Devo and Pluralism

Evolution as involving laws and inconceivable without them

Richard Creath (Arizona State University, United States)

There are those who say that there are no laws in biology and especially none in evolution. We are told that biology and evolution are “historical” fields, and such laws as may be appealed to must come from chemistry and physics or at least outside biology. While there is a great deal to be said for such claims, they are strictly speaking incorrect. This paper will show that for broadly Darwinian evolution by natural selection to provide an account of the origin of (current) species it must appeal to laws. And these laws are, at this level, fully biological. Whether such laws can or cannot be reduced to non-biological laws is irrelevant. The paper then goes on to argue that this conclusion is, to an important degree, compatible with the central point being made by those who say that there are no laws in biology.

Darwin’s tree diagram and its relation to his argumentative strategy and the doctrine of chance

Juan L. Bouzat (Bowling Green State University, United States)

Since the publication of the Origin of Species, there have been numerous debates about the specific nature of what Darwin called “My theory” and its relation to Special Creation as the main alternative explanation for the diversity of life. On the assumption that Darwin's Diagram of Divergence of Taxa represents a conceptual model of his theory, illustrating the causal efficacy of natural selection in producing well-defined varieties and ultimately species, I review Darwin’s argumentative strategy and scientific methodology. Although Darwin claimed that his research followed “true Baconian [inductive] principles,” he emphasized the importance of making observations in relation to supporting or rejecting particular ideas (hypotheses), what we now consider as the core element of the hypothetico-deductive method. I argue that the original representation of Darwin’s Tree Diagram in his “Big Species Book” demonstrates that Darwin followed a hypothetico-deductive strategy, framing his theory as an alternative to the doctrine of chance rather than Special Creation. Darwin’s allusion to Special Creation in the Origin of Species may be in part related to concerns regarding the reception of his theory by the Victorian society rather than to his argumentative strategy, since he assigned no explanatory power to the idea of Special Creation.

What evolutionary explanations can't do

Subrena Smith (University of New Hampshire, United States)

Evolutionary theory is taken by some to provide the explanatory platform upon which accounts of biological systems rest. If nothing in biology makes sense except in light of evolution, then explanations about organisms need to be consistent with or be framed in evolutionary terms. The idea is that the theory sets the options for what one can say about organisms. One can understand the theoretical and intellectual impulse for this idea, but it has been overextended. Evolutionary theory and explanations of biological phenomena framed in evolutionary terms are general-purpose origin accounts: they tell us (when they do) that traits of organisms and varieties of organisms came about through blind unintentional organic physical processes. That is all. Such explanations are not concerned with particular mechanisms (selection is not a mechanism in this sense). In this paper, I will argue that evolutionary explanations are unable to deliver on their promises of being informative. Such explanations can tell us no more than that features of organisms are the result of blind processes that produce certain effects—selection (although in some cases the questions are about whether a trait evolved or whether it is the result of non-evolutionary biological processes). My view is that important questions about features of organisms require proximal treatments, since knowing that a certain trait has a function (that it has historically performed that function) does not also show what causal factors made that function possible. I am therefore claiming that evolutionary explanations are often not informative and that the appearance of content in evolutionary explanations arises from the difficulty of keeping separate the distinction between functional explanations and mechanistic ones. This kind of fudging is especially salient in attempts to offer evolutionary accounts of human social behavior.