The Critical Rationalist                       Vol. 01  No. 04
ISSN: 1393-3809                                    31-Dec-1996

next 4 A Solution: Organismic Darwinism
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3 Darwin's Problem

... Nevertheless, such a conclusion [common descent], even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which most justly excites our admiration.

Darwin (1859, Introduction)

(9) With this continuation of the earlier quotation from Darwin the problem situation is now extended, in a crucial way. We arrive at what I shall term Darwin's Problem:

tex2html_wrap_inline1530 (Darwin):
Given that species descend from other species (i.e. given the theory of common descent), how is it that, in some cases at least, this descent has been accompanied by an increase in adaptive complexity?

(10) I introduce (albeit with some hesitation) the term adaptive complexity here, following Maynard Smith:

The main task of any theory of evolution (sic) is to explain adaptive complexity, i.e. to explain the same set of facts which Paley used as evidence of a Creator. Thus if we look at an organism, we find that it is composed of organs which are at the same time of great complexity and of a kind which ensures the survival and/or reproduction of their possessor. Evolution theory must explain the origin of such adaptations.

Maynard Smith (1969, p. 82)

(11) Popper (1978) has similarly formulated a version of tex2html_wrap_inline1530 by reference to Paley's famous "argument from design"--i.e. that the appearance of "Design" in the biological world "proves" the pre-existence of a designer or creator (which is to say, God). Popper emphasizes that Darwin himself acknowledged a strong influence from Paley's formulation (and attempted solution) of this problem.[1]

(12) Dawkins has adopted the terminology of "adaptive complexity" from Maynard Smith (Dawkins 1983, p. 404), and I shall use this phrase freely in what follows, but I shall also synonymously (?), and sometimes preferentially, refer to "inate" or "inborn" knowledge in the sense introduced by Popper:

I assert that every animal is born with expectations or anticipations, which could be framed as hypotheses; a kind of hypothetical knowledge. And I assert that we have, in this sense, some degree of inborn knowledge from which we may begin, even though it may be quite unreliable. This inborn knowledge, these inborn expectations, will, if disappointed, create our first problems; and the ensuing [somatic time] growth of our knowledge may therefore be described as consisting throughout of corrections and modifications of previous knowledge.

Popper (1961, pp. 258-259)

(13) tex2html_wrap_inline1530 refers to an increase or growth of adaptive complexity. I thus implicitly assume some notion of "degree" of adaptive complexity; but I require only that this can be defined a posteriori. That is, given two organisms, I suppose that I will, in general, be able to rank them (at least roughly) in terms of relative adaptive complexity. I specifically eschew any attempt to define an a priori measure of adaptive complexity.

(14) von Neumann has described a similar idea as follows:

There is a concept which will be quite useful here, of which we have a certain intuitive idea, but which is vague, unscientific, and imperfect ... I know no adequate name for it, but it is best described by calling it "complication." It is effectivity in complication, or the potentiality to do things. I am not thinking about how involved the object is, but how involved its purposive operations are. In this sense, an object is of the highest degree of complexity if it can do very difficult and involved things.

von Neumann
(1966 Fifth Lecture, p. 78, emphasis added)

(15) Maynard Smith has similarly endorsed this somewhat loose approach:

At the outset we are faced with a difficulty: we have no way of measuring the degree of complexity of a structure. Thus although most of us would readily agree that the organs of a man are more complex than those of an amoeba, and those of an amoeba more complex than those of a bacterium, we have no agreed criteria on which to base this decision, and no way of deciding by how much one organism is more complex than another.

It may therefore seem odd to start formulating a theory of evolution by introducing a term which cannot be fully defined. However, I see no escape from doing so. If organisms were not both complicated and adapted, living matter would not differ from dead matter, and evolution theory would have nothing to explain.

Maynard Smith
(1969 pp. 82-83, emphasis added)

(16) I consider that tex2html_wrap_inline1530 is the central, perhaps even the defining, problem of evolutionary biology, and is the problem Darwin hoped to solve with his theory of Natural Selection.[2]

(17) Before attempting to solve tex2html_wrap_inline1530 we must be clear as to how tex2html_wrap_inline1530 goes beyond the basic problems of the hierarchical relationships of similarity and geological ordering exhibited by biological organisms; that is, in what respect(s) the theory of common descent fails to address (much less solve) tex2html_wrap_inline1530 .

(18) Briefly, while the theory of common descent asserts the existence of a unique phylogenetic tree, tex2html_wrap_inline1530 goes on to ask: why does the phylogenetic tree has the particular structure that it has? Why, above all else, does it display at least some cases of increasing adaptive complexity?

(19) Note that the claim here is not that all evolutionary lineages have involved increasing adaptive complexity, but merely that at least some have. Similarly, even for those evolutionary lineages where there has been a net increase of adaptive complexity, there is no claim that this increase has occurred at a steady rate, or that it has been monotonic, or (most especially) that it will continue into the future.

next 4 A Solution: Organismic Darwinism
previous 2 Immutability and Common Descent

The Critical Rationalist                       Vol. 01  No. 04
ISSN: 1393-3809                                    31-Dec-1996

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TCR Issue Timestamp: Tue Dec 31 17:37:08 GMT 1996