Homeostasis, Complexity, and the Problem of Biological Design

The harmonious melding of structure and function-biological design-is a striking feature of complex living systems such as tissues, organs, organisms, even superorganismal assemblages like social insect colonies or ecosystems. How designed systems come into being remains a central problem in evolutionary biology. The prevailing explanation for biological design rests on essentially atomist doctrines such as Neodarwinism or emergence of complexity from self-organized systems of interacting agents. The Neodarwinist explanation for design, for example, posits that good design results from selection for "good function/structure genes" at the expense of "poor function/structure genes." Along the same lines, self-organization promises "order for free"-sophisticated structures and behaviors that emerge from simple interactions among agents at lower levels of organization. It is doubtful, however, whether such atomist doctrines by themselves can explain the origins of designed living systems. In this article, I argue that the missing piece of the puzzle is homeostasis, a classical concept that is not itself inherent in atomist explanations for adaptation and design. I couch my argument in observations on the emergence of a spectacular social insect "superorganism": the nest and mound of the macrotermitine termites, which can best be explained as the emergent product of agents of homeostasis. This poses interesting challenges to the prevailing reductionism that permeates our current thinking on design, adaptation and evolution. Introduction Among biologists, "design" refers to a peculiar coherence between a living structure and a function it performs (Turner, 2007). Bones, for example, are exquisitely constructed cantilevers, built to bear their loads with an elegant economy of form and materials (Currey, 1984), and it seems perfectly apt to say that bones are well-designed. Indeed, to describe them in any other way seems pedantic. Awkwardness attaches to the word, though, because "design" readily conjures up notions of a designer, that troublesome Master Craftsman that Plato introduced in his Timaeus, long the mainstay of natural theology, and that serves that purpose still for the resurgent "natural deism" that imbues Intelligent Design theory. Darwinism convincingly undercuts this type of thinking. Nevertheless, Darwinism is neither finished product nor holy writ, and there remain interesting and unresolved philosophical issues at its core. The most interesting is this very question of biological design: precisely why are living things so aptly constructed for the things they do? Darwinism, at least in its Neodarwinist conception, puts forth what is essentially an atomist answer to the question: biological design arises solely from the interplay of "atoms of heredity" in gene pools, converging over time onto well-functioning phenotypes through natural selection of particular well-function-phenotype-specifying genes. As in classical atomism, biological design is only apparent, and cannot be informed by any broader purposefulness (Dawkins, 1986). Standing in contrast to Neodarwinism's rather bleak vision is an older tradition in biology that puts the organism, not the gene, as the central fact of life. The unresolved issue of design rests in that vast terrain of physiology that separates genes from the well-functioning biological machines that mediate fitness. Much of this territory is terra incognita, but what is known about it exhibits a striking purposefulness, which today we call homeostasis, that seems quite at odds with the supposedly purposeless process that gives rise to it. This poses an interesting question for the atomist-minded Neodarwinist: is homeostasis "mere phenotype", the product of "homeostasis genes" that confer survival advantages? Or is it the other way round: is homeostasis the prime virtue that allows particular genes to thrive? The question is not trivial: In the one instance, evolution is really what Neodarwinism says it is: the playground of whimsical genes that have no purpose other than their own replication. …