In a new peer-reviewed paper in BIO-Complexity, Michael Denton challenges the view that biological organisms are accidents of random mutation and natural selection, instead adopting a structuralist view that body plans are like Platonic “types,” woven into the fabric of nature.

According to Denton, a biochemist and Senior Fellow with Discovery Institute’s Center for Science & Culture, this perspective, popular before Darwin wrote Origin of Species in 1859, “was not based, as Darwinists often claim, on a priori philosophical belief in Platonic concepts, but rather upon the empirical finding that a vast amount of biological complexity, including the deep homologies which define the taxa of the natural system, appears to be of an abstract, non-adaptive nature that is sometimes of a strikingly numerical and geometric character.”

This pre-Darwinian structuralism, he explains, “was supported by two fundamental observations: that the homologies appeared to be non-adaptive abstract patterns, and that in some cases they appear to have remained invariant for hundreds of millions of years in diverse lineages.” He gives the examples of the pentadactyl limb pattern in vertebrates, and the consistent patterns of the insect body plan, or the pentamerous symmetry of echinoderms.

The Darwinian view, in contrast, is “functionalist,” where “organisms are in essence like machines, complexes of functional parts arranged to serve particular adaptive ends.” Denton points out that the notion that the living world can be organized into an “ascending hierarchy” existed prior to Darwin. Does a structuralist view deny that adaptations exist? No, says Denton, for structuralism “implies that organic order is a mix of two completely different types of order, generated by two different causal mechanisms: a primal order generated by natural law, and a secondary adaptive order imposed by environmental constraints (by natural selection according to Darwinists, by Lamarckian mechanisms and by intelligent design according to current design theorists).”

But can Darwinism explain apparently non-adaptive features? Denton observes that Darwin saw them as “ancient adaptations no longer useful but incorporated into the genetic system and passed down through the generations.” According to Denton, Darwin’s argument is “more a case of special pleading than an ‘explanation,'” since Darwin nowhere “provide[s] any significant justification for this radical claim.” Darwin never explains why five digits are preferable to four or six digits. Indeed, Denton writes, “[t]here is still no detailed supportive scenario today, showing how these particular arrangements were adaptive in the ancestral species.” Thus the functionalism required by Darwinian evolution cannot ultimately account for seemingly non-adaptive features.

However the problem for Darwinism goes still deeper:

[E]ven if we could somehow account for the origin of such strikingly numeric patterns in adaptive terms we would then be faced with the additional and far more difficult problem of explaining how selection for function could have conserved the pattern for millions of generations after it ceased to have any adaptive significance.

Consider this. To accept Darwin’s legitimation we must assume that a fin — more specifically the arrangement of bones in a fish fin — underwent gradual adaptive change supervised by selection so that bit by bit the pattern approached and finally resulted in the pentadactyl pattern. While this process is at least conceivable (at least in the case of either the forelimb or hind limb), the next phase, which would involve the freezing of the pentadactyl pattern, is highly problematical. We have to believe that a variable adaptive form became an invariant, non-adaptive form at a particular instant in evolutionary time and was conserved through all the subsequent generations and phylogenetic lines in both fore and hind limbs.

Of course the challenge to functionalism is not restricted to providing an adaptive explanation for the pentadactyl pattern of the vertebrate limb. The same challenge is present in all attempts to explain the other homologous patterns, such as the numerology of the insect body plan or the concentric ring pattern of the angiosperm flower.

This problem for Darwinism should not go underappreciated, for Denton cites “the existence of a vast universe of non-adaptive forms and patterns in nature which no biologist, not even the most convinced functionalist or Darwinist, has ever claimed to serve specific adaptive functions.”

Thus:

In the context of what appears to be a veritable universe of non-adaptive form permeating all nature, the Darwinian assumption that the grand homologies once were adaptive in ancestral forms is self-evidently ad hoc. Put simply, neither Darwin nor any subsequent Darwinist has ever provided cogent reasons for accepting the grand claim that all complexity in biology (including all currently non-adaptive forms) has resulted from past adaptive and purposeful shaping of structures to serve functional ends.

So what can explain the origin of these features? Denton proposes that the structuralist perspective is due for rehabilitation, since “during the 20th century several advances in different fields have provided new support for the pre-Darwinian idea of life and its deep structures as immanent in the world order.” These discoveries include the fine-tuning of the universe for life, covered by Denton in a previous paper (BIO-Complexity, Vol. 2013 (1)). Here, Denton adds some new parameters from biochemistry. These include:

• DNA: The chemical stability of the double-helical shape of DNA which allows it to “perform one of the most important of biological functions,” including the fact that “its base sequence may contain ‘complex specified information.'”
• Protein folding: “the rules that generate the thousand-plus known protein folds have now been largely elucidated and remarkably they amount to a set of ‘laws of form’ of precisely the kind sought after by early 19th-century biologists.”
• Lipids: Lipid membranes “arise mainly from the self-organization of the membranes themselves, by energy minimization without any direction from anything like a genetic blueprint.”
• Microtubules: “The microtubular aster is another example of a molecular form that clearly arises directly out of the intrinsic self-organizing properties of its basic constituents.”

Denton explains that the specification of these structures in the genetic code is not enough to explain their functionality: “Although their constituents are specified in the genes, in no case is the three-dimensional, assembled structure specified by a genetic program. Rather, in every case the primary natural self-organizing propensity of a particular category of matter is exploited and secondarily modified to serve some adaptive end.” He further suggests that cell form, and even organismal form, might heavily depend on natural laws to take their shapes:

[T]o date the form of no individual cell has been shown to be specified in detail in a genomic blueprint. As mentioned above, between genes and mature cell form there is a complex hierarchy of self-organization and emergent phenomena, rendering cell form profoundly epigenetic.

Likewise, the fact that there is a genetic toolkit that organisms use for development “does not imply that there are blueprints in the genes specifying in exacting detail the forms of organisms.” In Denton’s view, “organic form at all levels of the biological hierarchy, not just at the cellular level, is essentially emergent and epigenetic, arising from complex dynamic self-organizing mechanisms during development.”

According to Denton, modern biology is rediscovering the laws of form predicted by structuralism.

Denton concludes that: “Although no biologist can deny that adaptation is ubiquitous in the living world, the Darwinian claim that ALL organic order, including the deep homologies, can be reduced to functionalist explanations is far from compelling. After 150 years of focused functionalist effort, the grand taxonomic system and the ascending hierarchy of homologous patterns has still not been adequately accounted for in functionalist/adaptive/Darwinian terms.”

The structuralist view of biology he proposes is not exactly the same as some intelligent design arguments, but it entails a designed universe, where the laws of nature are finely tuned to allow for complex life to exist. Just as Darwinism cannot explain these laws, the laws themselves cannot explain all the adaptive complexity of life. Structuralism, in short, leaves plenty of room for intelligent design.

Image credit: Thomas Tolkien, Bernat Casero/Flickr.