Biology and Philosophy by MJ DENTON

It is generally acknowledged that all organic beings have been formed on two general laws—Unity of Type and the Conditions of Existence. By unity of type is meant that fundamental agreement in structure, which we see in organic beings of the same class which is quite independent of their habits of life.…
—Charles Darwin (1872) Origin of Species, 6th Edition.

Most organisms are well adapted to their immediate environment [conditions of existence], but also built on anatomical ground plans that transcend any particular circumstance. Yet the two principles seem opposed in a curious sense—for why should structures adapted for particular ends root their basic structure in homologies that do not now express any common function.
The designation of one principle or the other as the causal foundation of biology virtually defines the position of any scientist towards the organic world and its causes of order . . . Shall we regard the plan of high level taxonomic order as primary, with local adaptation viewed as minor wrinkles upon an abstract majesty. Or do the local adaptations build the entire system from the bottom up? This dichotomy set the major debate of pre-Darwinian biology.
—Stephen J. Gould

If we are forced (by some aspect of universal structure, psychic necessity, or merely the norms of Western culture) to order our world by dichotomies, we may at least choose some grand divisions that bring clarity to our subjects and insights to ourselves. Sterile dichotomies are established as debating points to make one side (usually invented) look foolish, and the other (our own) undeniably right and just. Great dichotomies [between the formalist and functionalist conception of life] make even divisions between alternatives with intellectual punch and strong empirical backing. Neither side is right; both are infallibly interesting....
—Stephen J. Gould

Introduction

For two centuries biologists have been divided into two opposing camps regarding the fundamental nature of organic form—the formalist (or structuralist) and the functionalist. According to formalism much of the order of life is the result of basic physical constraints arising out of the properties of matter; more specifically bio matter. These constraints limit the way organisms are built to a few basic designs. And this implies that life’s basic forms arise in the same way as that of other natural forms such as galaxies or atoms from the self organization of matter and are genuine universals. Formalists adhere therefore to a strictly “nonselectionist, nonhistoricist” view of the biological world. Leading 20th century formalists include D’Arcy Wentworth Thompson, Rupert Riedl, Brian Goodman and Stuart Kauffman . According to the opposing paradigm, functionalism, the main designs of life are not the result of physical law but rather the result of specific adaptations built by selection or historical contingencies (previous specific adaptations in ancestral forms). This is of course the currently prevailing view. All Darwinists, and hence the great majority of evolutionary biologists, are functionalist by definition, as evolution according to Darwinism comes about from adaptation to serve specific biological functions. In this essay I review and defend the formalist position by arguing that one set of important biological forms the deep homologies have never been satisfactorily reduced to functionalist explanations.

Pre-Darwinian Formalism

The discovery that the living world is organized into an ascending hierarchy of ever more inclusive classes each defined by a particular unique homology or suite of homologies of an apparently abstract nature was one of the major achievements of pre-Darwinian biology. Although the causal basis of this remarkable hierarchy was unknown (and is still today) it was widely assumed in the early 19th century that it was an immanent feature of nature and part of the eternal order of the world. As Mary Winsor points out, just as Newton had provided a causal explanation for the regularities in the motions of the planets described by Kepler, so biology would eventually have its Newton who would provide a scientific explanation for the hierarchic pattern of nature. As she comments: “Many biologists seemed to feel that although their field was not yet as exact, coherent and logical as Newtonian science, it had the potential of becoming so…. The role of a scientist was to discover within the confusing diversity of living things the underlying order and lawfulness.”

The idea that life on earth was the result of a lawful natural process was explicitly affirmed by Richard Owen (1866) in the concluding chapter of his Anatomy of Vertebrates when he claimed that the path of evolution path was “preordained … due to an innate tendancy … by which nomogenously created [generated by law] protozoa have risen to the higher forms.” And Owen was no exception. William Carpenter, one of Owen’s contemporaries, believed as Dov Ospovat points out in his Development of Darwin’s Theory, “that the laws that define the plan of creation were … impressed on matter in the beginning which brought about the creation of the universe and the creation and succession of life.” As Russell shows in his classic Form and Function nearly every pre-Darwinian biologist—including such luminaries as Karl Ernst von Baer, Etienne Geoffroy St. Hillaire, Henri Milne-Edwards, E. Serres, J.F. Mekel, Carl Gustave Carus, H.G. Bron, Theodore Schwann—, and many after Darwin particularly on the continent, such as Ernest Haeckel, believed life’s overall order to be the result of lawful, if unidentified, processes. The concept that life’s hierarchic pattern is inherently lawful is also witnessed in the attempt of early 19th-century taxonomists to organize classification schemes in terms of geometric and numeric patterns such as the quinarian system of William Sharp Macleay and Swainson. Even Huxley was attracted to these orderly circular systems and his remark that “the circular system appears to me to stand in the same relation to the true theory of animal form as Kepler’s Laws to the fundamental doctrine of astronomy” serve to underline further that the core aim of early 19th-century biology was to find lawful explanations of the biological realm. As Mary Winsor comments regarding Huxley: “He had not found the answer, biology’s law of gravity, but he was searching in that direction.” However anomalous it may seem in the context of today’s biology, profoundly wedded as it is to functionalist notions and the concept of life as artifact (see section below on Darwinism) the belief that the order of life is immanent in the fabric of things was the very Zeitgeist of early 19th-century biology.

Homologous ‘Numerology’

The formalist claim that the homologous patterns (and the grand hierarchic system) are immanent features of the changeless order of nature was not based on an a priori adherence to Aristotelian or Platonic theories of nature (see section on Essentialism below). On the contrary the formalist position was based on 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. Owen famously termed the homologies ‘Primal Patterns’ in his great classic On the Nature of Limbs, a phrase which wonderfully captures what he and many other pre-Darwinians saw them as essential changeless natural forms or types no less ‘lawful,’ no less changeless, and no less immanent features of the order of the world than atoms or crystals or any other set of natural forms. In chapter fourteen of the Origin, Darwin describes a number of homologous patterns including the well known pentadactyl limb (see Figure 1): “What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include similar bones, in the same relative positions?” That such homologous patterns have no apparent specific adaptive utility in any living organisms was admitted by both Darwin and Owen. As Darwin comments in the Origin, “Nothing can be more hopeless than to attempt to explain this similarity of pattern [the homologies] of members of the same class, by utility or by the doctrine of final causes [adaptation]. The hopelessness of the attempt has been expressly admitted by Owen in his most interesting work on the ‘Nature of Limbs.’”

Fig 1. Homology:

The Pentadactyl Limb. Showing the limbs of several tetrapod species to illustrate the underlying pentadactyl design. (From Monroe W. Strickberger, Evolution (Sudbury, MA: Jones and Bartlett Publishers, 2000).
http://www.pbs.org/wgbh/evolution/library/04/2/l_042_01.html

Nothing emphasizes the “hopelessness” more obviously than the curious numeric and geometric aspects of so many homologous patterns. Consider the weird ‘numerology’ of the insect body plan. The insect body is divided into 3 parts, head, thorax and abdomen. The thorax consists of 3 segments and each bears a pair of legs, six altogether. Eleven segments can be recognized in the abdomen of most juvenile insects and although some insect adults—including coleopteran (beetles) and hymenopteran (wasps, bees, ants, etc.)—have less than eleven, no insect has more than 11. The legs of all insects consists of 5 components namely; the coax, the trochanter, the femur, the tibia, the tarsus, the tarsus itself is typically divided into 5 subsegments. The insect mouth in all the many diverse species always consists of 4 parts from front to back—the labrum, the mandibles, maxillae, and the labium. And all insects possess 2 antennae and they are mobile jointed appendages.

Homologous ‘numerology’ is not limited to the insects or the pentadactyl limb. In the case of the cephalopods for example the Octopoda (octopi) have 8 tentacles while the Teuthoidea (squids) have 10, two of which are considerably longer than the other 8. Again octopi and squids have 2 gills while other cephalopods including Nautilus have 4. The echinoderms (starfishes and sand dollars) exhibit a pentamerous symmetry. Among the Cnidaria (jelly fishes, sea anemones and corals) there are a great variety of intriguing radial symmetries. Among the Scyphozoa (jelly fishes), most exhibit a tetramerous symmetry “having their parts symmetrically repeated round their oral aboral axis to the number 4 or multiples of 4 … [however some species] are built on a plan of six, and have a hexamerous symmetry.” Again among the Anthozoa (sea anemones and related polypoid forms), different classes are differentiated by different types of radial symmetries and can be classified on number and arrangement of tentacles and mesenteries and number and arrangement of septa. One colonial subclass (Alcyonaria) possess 8 pinnate tentacles forming a marginal circle on the oral disc and eight mesenteries attached to the gullet. “The eight symmetrically arranged tentacles and mesenteries give the polyp what seems to be an octamerous radial symmetry.” Another subclass the Zoantharia (sea anemones) are subdivided into a variety of groups exhibiting complex six-fold symmetries with “mesenteries in cycles of 6, 12, or multiples of 6.” The textbooks of invertebrate zoology are full of innumerable additional examples.

The basic divisions within the vertebrata are also defined by homologous patterns that are no less numeric than in the invertebrates. We have already referred to the pentadactyl limb of the tetrapods. Among mammals the number of cervical vertebra is 7 in nearly all placental orders including the giraffe, mouse, whale, elephant and human. Most placental mammalian orders have no more than 44 teeth and these are subdivided into molars, pre molars (possessing cusps) canine and incisors (only the Cetacea depart markedly from this formula). Again in all placental mammals the cerebral cortex is divided into six layers of cells or laminations.

Invariance

In addition to their remarkable abstract character, the other striking feature of the homologies is their great stability through millions of generations and in diverse phylogenetic lines. The pentadactyl limb, for example, first emerged some 400 million years ago and has remained essentially invariant in all tetrapod lines ever since. The plan of the Angiosperm flower has remained unchanged for 100 million years since the late Cretaceous when the first flowers emerged at the end of the reign of the Dinosaurs. The defining features of the insects and the various insect subgroups like the ants has also remained constant for millions of generations. The abstract nature and deep invariance of the homologies and the types which they define is a fact, a simple straightforward biological fact. However remarkable it might be— and it is certainly very remarkable in Darwin’s own words “curious” and “striking”—it was in the early 19th century and it is still today a fact based on observation.

Adaptive Masks

Despite their focus on the apparently abstract homologous patterns neither Owen nor any of the other pre-Darwinian formalists denied the fact of adaptation nor its significance, but they saw adaptation to be a secondary peripheral phenomena the result not of natural law (order from within), but of environmental conditions (imposing an external order from without). Owen coined the elegant descriptive term ‘Adaptive Masks’ to highlight their superficial and secondary nature compared with the underlying ‘Primal Patterns’ upon which they were crafted to serve various adaptive functions. While the primal patterns were seen to be part of the changeless and lawful world order the variant ‘Adaptive Masks’ were assumed to be imposed by various environmental necessities. As Russell (1916) points out, Haeckel for example distinguished “the internal Bildungstrieb. [formative force] … the mechanical effect of the material structure of the crystal or the germ, and adaptation, or the external Bildungstrieb, [which he saw as] modifications induced by the environment.” Goethe’s view was similar. Goethe asserted the primacy of formal patterns while also conceding the vital if secondary role of adaptation. As Gould comments, “internal formation acts as the primary source that ‘must find external conditions’” In Goethe’s words: “We can best see this in a species of seal whose exterior has taken on a great deal of fish character [adaptive form] while its skeleton [formal structure] still represents the perfect quadruped.” Environmental adaptation was also seen by H.G. Bron as one of the major causal factors shaping organic form.

The Metaphor of the Crystal

Given the lawful Zeitgeist of pre-Darwinian biology and given the enigmatic abstract nature of the homologies and their invariance in so many diverse kinds of organisms and through such vast periods of time it was a small inferential step to view them as changeless natural forms analogous to crystals or atoms. Geoffroy, perhaps the leading continental formalist assumed the homologies to have “powers” analogous to atoms and other unalterable elements of the physical world. Owen also used the crystal analogy unambiguously in the final chapter of his Anatomy of Vetebrates (1866) in the context of a discussion of the causes of segmentation: “The repetition of similar segments in a vertebral column and of similar elements in a vertebral segment, is analogous to the repetition of similar crystals”. The metaphor was also used by Theodore Schwann the co-founder of the cell theory. In the last chapter of his Microscopical Researches he draws extensive parallels between cells and crystals:
The process of crystallization in inorganic nature … is … the nearest analogue to the formation of cells … should we not therefore be justified in putting forward the proposition that the formation of the elementary parts of organisms is nothing but a crystallization and the organism nothing but an aggregate of such crystals … if a number of crystals capable of imbibition [absorption] are formed, they must combine according to certain laws so as to form a systematic whole, similar to an organism.
The metaphor was used extensively by Haeckel who, echoing Schwann, talks of “cells as organic crystals, of crystal trees, of the analogy between assimilation by the cell and the growth of crystals in a mother liquid.”

Note: The fact that many different crystal forms can be generated from a small number of basic patterns added to the attraction of the analogy. In the case of calcite, for example, the rules permit the construction of about 600 different molecular arrangements which can be combined to build over 2000 different combinations.

Believing the homologies to be lawful features of the world order no less than atoms or crystals, pre-Darwinian biologists sought to provide a rational and lawful account of the diversity of organic forms in terms of ‘Laws of Biological Form.’ Just as today we account rationally for the diversity of inorganic forms such as atoms, crystals, chemical compounds, and even subatomic particles by various sets of laws or constructional rules—atom building rules, laws of crystallography, laws of chemistry and so forth—which allow for a rational deductive derivation of all possible atoms, crystals, chemical compounds, subatomic particles etc. Typical of the search for these elusive laws was the attempt of C.G. Carus, H.G. Bronn and E. Haeckel to develop what Russell terms a “’theoretical’ morphology of living things, after the fashion of the morphology of crystals with their sixteen possible Types.”
Essentialism Story
There is no doubt that the current widespread impression that pre-Darwinian formalists derived their belief that the deep homologous patterns were changeless natural forms or types (no less than crystals or atoms) on all sorts of discredited metaphysical beliefs has been severely critiqued by recent researchers and shown to be largely a myth created by 20th-century advocates of the neo-Darwinian evolutionary synthesis. As Amundson shows, whatever their metaphysical leaning, the concept of the type as a basic natural form was not derived from any a priori theories of nature (idealistic morphology, transcendental anatomy, essentialism, Platonism, creationism, etc.) but on solid empirical observations. As he comments, “They do not deserve the disdain to which they have so long been subject.…

We will fret over their metaphysics no more than we fret over Kepler’s.” The formalist conception of life and especially of an ascending hierarchy of taxa of ever widening comprehensiveness as immanent features of nature was close to the classic Aristotelian world view but it was based on the facts not on a philosophical a priori.
Although the “Laws of Form” biology of the pre-Darwinian era with its emphasis on evolution by natural law and its conception of a rational order underlying the diversity of life, represented a grand scientific vision, whose heroic goal was nothing less than the unification of biology and physics. It collapsed primarily because it failed to identify the elusive laws of form which might have provided a rational account of organic form and explained how the evolution of the basic types, from cell forms to the body plans of the major phyla, and deep homologies such as the pentadactyl limb, might have been generated by natural law. That they had no convincing explanation was explicitly conceded by Owen in the final paragraph of On the Nature of Limbs (1849): “To what natural laws or secondary causes the succession and progression of such organic phenomena may have been committed we as yet are ignorant.”

The Darwinian Revolution

The failure to find the laws of form which would account for the basic forms of the biological world and explain the course of evolution opened the door for Darwin and ushered in the functionalist revolution. After 1859 the formalist conception of the basic order of the biological realm as a product of natural law was overthrown and with it the pre-Darwinian concept of organisms as real natural existents, as necessary parts of the eternal fabric of the world order, like atoms or crystals was abandoned. Instead a new model of organic form—that of the machine or artifact—took its place. Necessity was replaced by contingency and natural law was replaced by natural selection. Organic forms were now viewed as contingent mutable assemblages of matter, like the constructs of a child’s erector set such as Lego, put together during the course of evolution piece by piece by natural selection. The adoption of the ‘contingent mutable artifact’ as the metaphor of organic form ushered in the modern era of biology and changed the whole explanatory framework of biological science from what was a formalist/functionalist framework (primal abstract patterns by law, adaptive masks by environmental selection) to a purely functionalist conception of nature. The very naturalness of life—the idea of life as a necessary part of nature—was abandoned. The metaphor of the crystal was replaced by that of the watch!

Legitimations

But if functionalism is to provide a comprehensive explanatory framework of ALL biological order it must be capable of accounting plausibly not only for adaptive complexity but also for the existence of non-adaptive order including the universe of apparently afunctional homologies which underlie the whole natural system. Darwin’s explanation is that they represent ‘leftovers’ of evolution; ancient adaptations no longer useful but incorporated into the genetic system and passed down through the generations. Darwin gave this explanation for persistent pattern which has no apparent adaptive utility in many places in the

Origin of Species:

The chief part of the organization of every living creature is due to inheritance, and consequently though each being is well fitted for its place in nature, many structures have now no very close and direct relation to present habits of life. We cannot believe that the similar bones in the arm of a monkey, in the fore-leg of the horse, in the wing of a bat, and in the flipper of the seal, are of special use to these organisms. We may safely attribute these structures to inheritance. [my emphasis]
If we suppose that an early progenitor—the archetype as it may be called—of all mammals, birds, and reptiles, had its limbs constructed on the existing general pattern, for whatever purpose they served, we can at once perceive the plain signification of the homologous construction of the limbs throughout the class. [my emphasis]

Clearly Darwin’s ‘explanation’ is more a case of special pleading than an ‘explanation.’ On the one hand he admits with Owen that the homologies serve no adaptive purpose (see discussion above), but is prepared to speculate that they did once serve some purpose in ancestral forms. But nowhere in the Origin does he attempt to provide any significant justification for this radical claim by showing for example that five fingers were adaptive in the ancestral tetrapod, or that the three thoracic segments were adaptive in the ancestral insect. Given their numeric and geometric character to show that the homologies were once upon a time adaptive poses a Herculean challenge to the functionalist framework. Moreover in chapter 6 of the Origin he concedes “that many structures are now of no direct use to their possessors, and may never have been of any use to their progenitors”—a concession which largely undermines his position.

Consider the origin of the pentadactyl pattern. To provide a strictly functionalist explanation of the origin of this pattern Darwin would have had to give an adaptive explanation for each element of the pattern; to explain why 5 digits were preferred over 4 or 6! Why 2 distal bones were preferred over 1 or 3 or 4 and one proximal bone over 2 or 3? In the end we have no explanation. If they were adaptive in the ancestral species we cannot imagine why!

Moreover the forelimbs and hind limbs are based on the same homologous pattern. Brian Goodwin comments: “Given the diversity of uses one might have expected that natural selection would have designed each limb to optimally serve its functions.” Why should selection pressures on a forelimb and hind limb—that are different in EVERY limbed species—have miraculously generated the same functional form in both the hind limb and fore limb in the mysterious ancestral species? Similar problems are faced in accounting for the specific adaptive significance of ALL the universe of homologous patterns in nature.

Figure 2. Radiolarian shells from Ernst Haeckel’s Kunstformen der Natur (Artforms of Nature), 1904.

But even if we could somehow account for the origin of such obviously numeric patterns in adaptive terms we are then 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: 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 relatively plausible the next phase which involved 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 without subsequent change through all the subsequent generations and phylogenetic lines.
 

The Ubiquity of Non-adaptive Pattern

A peculiarly difficult challenge to Darwinian and functionalist assumptions that the deep homologies were adaptive in ancestral forms (essential if selectionism is to be as Darwin claimed the engine of evolution) is 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 were ever functional. This raises the obvious problem on what grounds can the homologous patterns like the pentadactyl limb—–be differentiated from the host of patterns which no one doubts are afunctional.

To take one example, the shells and tests of unicellular organisms including radiolarian, formanifera and diatoms (see Figure 2). These display a bewildering universe of diverse forms some highly geometric but others as abstract as a Kandinsky painting. That many of these forms are abstract structures produced by the direct action of physical law, no less than the generally round shape of a cell, was wonderfully argued in D’Arcy Thompson’s On Growth and Form. As Thompson argues
The forces that bring about the sphere, the cyclinder or the ellipsoid are the same yesterday and tomorrow. A snow crystal is the same today as when the first snows fell. The physical forces which mold the forms of Orbulina, of Astrorhiza, of Lagena or of Nodosaria today were still the same, and for aught we have reason to believe the physical conditions under which they worked were not appreciably different , in that yesterday we call the Cretaceous.
Gould confers as he comments: “These forms [radiolarian and foraminferan tests] are… no more…subject to specific accounts of historical filiation than are the varied shapes of snow flakes or quartz crystals.” But it is not just in the unicellular world that nature abounds in abstract formal patterns. Even on the most cursory and passing observation of the forms of life and the patterns of nature, that might be observed in any suburban garden, it is obvious that a vast amount of biological order is non-adaptive. In the context of the veritable universe of non-adaptive form permeating all nature, Darwin’s assumption that the homologies were adaptive in ancestral forms is an ad hoc case of cherry picking. Put simply: Darwin failed to justify his grand claim that ALL complexity in biology (including all currently non-adaptive forms) has resulted from past adaptive and purposeful shaping of structures to functional ends.

In sum: Whatever might be the explanation of the deep homologies which unite each of the main taxa in the natural system and whether they are indeed generated by laws of form as radiolarian shells undoubtedly are there is no question that neither Darwin nor any subsequent Darwinist has provided any convincing functionalist explanation. Nonetheless, since Darwin, biology has been tightly wedded a priori to a functionalist/adaptational conception of living nature and avoided the challenging possibility that much of the order of nature might be fundamentally non-adaptive and beyond even in principle functionalist explanations. So Darwinian biologists conforming to the priority of the paradigm prefer to look the other way. The grand fact of non-adaptive order is the great nemesis, the Achilles heel of the whole functionalist tradition. Accept formal patterns as the primary fact of biology, the primary phenomenon to be explained and Darwinism becomes a special theory explaining only adaptation and nothing more.

Recent Support for Formalism

Formalism may have been largely sidelined in the English speaking world since the Darwinian revolution, but it has refused to die. Rather during the past fifty years several developments have provided new support for the pre-Darwinian idea of life and its deep structures as immanent in the world order. Firstly there is the discovery of the anthropic coincidences which imply that the laws of nature are fine tuned for life as it exists on earth; secondly there is the molecular biological revolution which has revealed that many of the core constituents of the cell are natural forms determined by the laws of nature, i.e., formal structures; and thirdly the discoveries in developmental biology which have provided additional support confirming the developmental robustness of homologous patterns.

The Fitness of the Cosmos for Life

As many astronomers and physicists have recently pointed out, advances in 20th-century physics and astronomy have revealed that life as it exists on earth is dependent on a peculiar fitness in the basic laws of physics which gives the impression that these have been specifically designed to generate a cosmos specifically adapted for life. If the various fundamental forces and constants which determine the structure of the cosmos and the properties of its constituents did not have precisely the values they do there would be no stars, no supernovae, no planets, no atoms, no life. As Paul Davies summarizes:

The numerical values that nature has assigned to the fundamental constants, such as the charge on the electron, the mass of the proton, and the Newtonian gravitational constant, may be mysterious, but they are crucially relevant to the structure of the universe that we perceive. As more and more physical systems, from nuclei to galaxies, have become better understood, scientists have begun to realise that many characteristics of these systems are remarkably sensitive to the precise values of the fundamental constants. Had nature opted for a slightly different set of numbers, the world would be a very different place. Probably we would not be here to see it.
More intriguing still, certain crucial structures, such as solar-type stars, depend for their characteristic features on wildly improbably numerical accidents that combine together fundamental constants from distinct branches of physics. And when one goes on to study cosmology—the overall structure and evolution of the universe—incredulity mounts. Recent discoveries about the primeval cosmos oblige us to accept that the expanding universe has been set up in its motion with a cooperation of astonishing precision.
And the fitness of the cosmos for life does not stop with simple microbial life it extends even to higher organisms like ourselves. This revolutionary new evidence is certainly compatible with the pre-Darwinian conception of life as immanent in the world order; with Owen’s conception that “nomogenously created [generated by law] protozoa have risen to the higher forms” and with the widespread idea that the main taxa were invariant universals analogous to atoms or crystals. If the laws of nature are, for whatever reason, miraculously fine tuned to generate environmental conditions ideally suited to the forms of life that exist on earth, it is surely not so outrageous to envisage that they might be also fine tuned to generate the grand hierarchy of forms themselves.

Molecular Typology

Another major development over the past few decades has been the revelation that at a molecular level much of the fundamental order of life arises from the self organization of matter and NOT by natural selection. Even the icon of molecular biology, the double helix itself, is unquestionably a natural form determined in all its exquisite geometry by the laws of chemistry and physics. It may perform one of the most important of biological functions but its structure and properties arise from the self organizing properties of matter and not by selection for function. Both its double helical structure and its chemical stability conferring upon it such a wonderful fitness for its genetic role are all determined by natural law. During the 1960s the structure of two other important self-organizing biological structures were elucidated—the 1000 protein folds and the bilayer lipid membrane that forms the outer boundary of all living cells (and the bounding membrane of most of the important organelles in the cell, including the nucleus and the mitochondria). The 1000 protein folds are also like the double helix, determined by natural law, and represent a set of natural forms. It is now known that their forms arise again like that of the double helix from the self organizing properties of matter. Intriguingly the rules that generate the protein forms 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 formalists (see above). In conformity with pre-Darwinian formalism the protein forms are strikingly analogous to a set of crystals! And while all proteins exhibit adaptive modifications these are again clearly ‘Adaptive Masks’ built upon on an underlying invariant form or ‘Primal Pattern’. In the case of the bilayer lipid membrane it is again clear that its basic form arises spontaneously from the physical properties of its basic constituents. Lipid membranes form a vast variety of tubes, vesicles and various types of sheets. All this zoo of forms arises spontaneously by self-organization from the physical properties of various bilayer lipid membranes of differing chemical composition.

Developmental Robustness

It has been known since Abraham’s Trembly’s dramatic studies in the 18th century on the regeneration of Hydra that the native forms of organisms may be arrived at via several different routes. In his classic book defending vitalism, Driesch cites many cases. As Amundson comments: “Regenerated organs are clearly homologous to those originally developed in embryos, but they are constructed in a different manner and arise from different tissue sources.” This can only mean that at least in the same species homologous structures or wholes are more robust and invariant than their parts or the variable developmental processes by which they emerge and this has always lent support to the formalist notion that the homologies are robust natural kinds.
Fig 3. Two Ways to Make an Insect. Illustrating the way segments are generated in short germ- band and long-germ band embryos. In the case of the short germ band insects the segments are generated sequentially (A, B and C). In the case of long germ band insects the segments are generated simultaneously. In the long germ band embryos a gradient of morphogens is set up in the embryo (A). This gradient determines the expression of various ‘segmental genes’ including ‘pair rule genes’ (B), and then ‘segmental polarity genes’, (C). The end result of both generative systems is the same segmental pattern (D).
After I. Salazar-Ciudad, R.V. Sole, S.A. Newman (2001) “Phenotypic and dynamical transitions in model genetic networks II. Application to the evolution of segmental mechanisms,” Evolution and Development 3:2, 95–103.

It has also been apparent for many years from comparative studies that the same homologous structure may arise in different ways in different species. To take a classic example: The early embryos of all vertebrates are very similar at the post gastrula stage when the vertebrate body plan is first apparent but the developmental processes and pathways that lead to this homologous stage differ markedly in different classes. Or again among beetles for example: although the segmentation pattern of all adult beetles is the same 3 thoracic segments, 11 abdominal segments, three different generative mechanisms are used to generate segments in different beetle species; the so called short germ-band, intermediate germ-band and short germ-band. In the long germ-band mechanism the entire anterior-posterior segmentation pattern is determined simultaneously in the embryo while in the short germ-band the successive segments are generated by successive subdivision of a posterior growth region (see Figure 3). In one case the spatial sequence is formed at the same time whereas in the other the spatial sequence is also a temporal sequence. Many more examples could be cited. As Amundson comments: “Homologous characters do not always arise at corresponding times in ontogeny, or develop out of the same embryological precursors or even the same germ layers, or reflect expression of the same genes. Information from anatomy, embryology and genetics can give inconsistent answers when one is trying to determine the homology of a character.”

As a result of recent advances in developmental biology over the past two decades (which have led to the discovery of the universal tool kit of genes and gene circuits and to the launch of the new field of evolutionary developmental biology, or evo-devo), we now know a great deal about the genetic processes underlying the development of such classic homologies as the pentadactyl design or the insect body plan in different species. This new knowledge has not provided any support for functionalist assumptions and this is evident in the skepticism regarding Darwinism which is widespread in evo-devo circles. On the contrary it has revealed many new examples of the stability of homologies in the face of different generative processes in different species providing further support for the notion that the homologies are robust natural kinds. As Gunter Wagner (a leading authority in the field of evolutionary developmental biology) comments,

Developmental mechanisms and pathways have a tendency to shift under the continuing presence of the developmental types. The genetic machinery that produces segments in grasshoppers is in important ways different from that in a fruit fly. Genes which are essential for fruit fly segmentation in fruit flies are not even expressed in grasshoppers, e.g., even skipped and ftz. [my emphasis]
In Sum: It is now clear that not only may homologous structures be reached in different ways in the same species but by different developmental mechanisms in different species.

It was always apparent that the adaptations built upon the homologies (like the various vertebrate limbs built upon the underlying pentadactyl pattern) are far more variable than the underlying homology itself. It is now clear that in many instances the homologous patterns also are more robust than the underlying generative process and gene circuits which assemble them during development. This is truly remarkable. There is variation above (the various adaptive forms built upon the homology in different species) and variation below (the variable generative processes by which the homologous pattern is derived in development in different species) while the homologous pattern itself remains invariant across the species in which it is manifest! Acting like ‘strange attractors,’ the homologies exert a mysterious determinate influence on the biomatter in which they form. Whatever the reason for their curious robustness there is no doubt at present that as Wagner admits: “there is still no explanation for the stability of the developmental type.… [Giving an explanation is] the most urgent theoretical problem in the unification of development and evolution .” [my emphasis].

Taken together: the strange fitness of the laws of nature for life as it exists on earth revealed by advances in 20th cosmology and fundamental physics; the revelation of the mid-20th-century molecular biological revolution that many of the core molecular and cellular forms underlying all life are purely natural forms (formal structures) the result of the self organization of matter; the recent advances in developmental biology showing that the deep homologies are developmentally robust, i.e., stable in the face of instability in their generative mechanisms, provide strong support for the formalist view.
Any final validation of the formalist position will only come with further advances in biological knowledge especially in the area of cellular and developmental biology. But when this consilience of new evidence is considered in the context of the strikingly abstract numeric and geometric character of the homologies and the 200-year failure of functionalists—including Darwin himself—to provide any genuine explanation for their origin and stability in functionalist terms, the possibility that formalism will turn out to be more than just a formidable current competitor to the pan-selectionist paradigm, but ultimately capable of providing overall a more coherent explanatory framework of the order of life and especially for the grand ‘homological hierarchy’ which underlies the natural system, cannot be discounted. The metaphor of the crystal may yet eclipse the metaphor of the watch.

An Echo of Aristotle

The validation of the formalist position—that the forms of life are immanent in nature and arranged in an ascending hierarchy of ever more inclusive forms—would not only severely undermine the Darwinian claim that selection is the creative engine of evolution, but would also have deep philosophical implications touching many other areas of thought.
One intriguing outcome would be the support such a validation would provide for Aristotelian natural philosophy. The formalist notion that nature consists fundamentally of an immanent ascending hierarchy of natural forms is almost ‘pure Aristotle.’ As Hans Jonas shows in his classic The Phenomenon of Life, the classical Aristotelian system of the world was one of wholes within wholes of ever widening comprehensiveness, culminating in the cosmos himself, the ultimate all embracing whole, the supreme “One in Many” of his own end. The consonance with formalist conceptions is obvious.

In addition the robustness of the homologies—their invariance in time and in the face of variance of their parts and generative processes—is consistent with their being natural wholes possessing, in Jonas’ words, a “wholeness as an autonomous cause with respect to [their] component parts and therefore the ground of [their] own becoming” is again pure Aristotle. For as Jonas points out the primacy of the whole over its parts was an integral part of the classical world view: “The whole spirit of Greek natural philosophy … dwelt on complete structures of form, with an autonomous status to their wholeness.”

Jonas, who as a convinced Aristotelian accepted the primacy of wholes over their parts, was opposed to the reductionist approach of modern science which, since Descartes and Newton, has seen the main aim of science to provide explanations of nature in terms of fundamental particles and forces and presumes that higher order biological forms including humans are epiphenomenal—mere incidental combinations of lower level processes. The possibility of a reinvigorated formalism would therefore have greatly pleased Hans Jonas representing as it does an important first step towards a new Aristotelian synthesis and away from the reductionism of modern science.

ABSTRACT

Many pre-Darwinian biologists belonging to the so called ‘formalist tradition’ viewed the invariant homologies underlying the adaptive diversity of life to be immanent features of nature ie., natural kinds —–analogous to atoms or crystals—–which Owen termed ‘Primal Patterns.’ The formalist world view of pre 1859 biology and the concept of a ‘lawful biology’ was not based as Darwinists often claim on a priori philosophical belief in substantial form or Platonic concepts but rather upon the empirical finding that a vast amount of biological complexity - including the homologies which define the taxa of the natural system - appears to be of an abstract non-adaptive nature sometimes of a strikingly numerical and geometric character which is difficult to account for in functionalist terms. Not only are these defining homologies apparently non-adaptive but even more significantly they exhibit an extraordinary robustness and stability having in many instances remained invariant in diverse lines for millions of years while the adaptations built upon them exhibit enormous variation. It is this persistence of the defining characters of taxa that makes biological classification possible and allows the construction of phylogenetic trees. Darwin conceded that these homologies are non-adaptive in presently existing organisms but his explanation that they were once adaptive in ancestral forms has never been validated. Over the past several decades a number of developments in fundamental science has provided new support for the formalist position. Firstly there is the discovery that the laws of nature appear to be fine tuned for life as it exists on earth – a discovery which is consistent with the formalist conception of life as an immanent feature of nature. Secondly there are the advances associated with the mid 20th century molecular biological revolution which have revealed that at a molecular and cellular level a considerable amount of biological complexity is clearly determined not bit by bit by natural selection but by natural law, more specifically by the laws of chemistry and physics, which govern macromolecular structure. The protein folds, various membrane forms and even the form of the double helix itself are natural forms whose life giving properties and beautiful geometries arise like those of atoms and crystals from the changeless self organizing properties of matter. Thirdly there is the remarkable fact that despite the recent increase in our knowledge of the developmental genetics of many of these ‘Primal Patterns’ including such diverse examples as the pentadactyl limb, the angiosperm flower and the ground plan of the butterfly wing the challenge remains; neither the origin, nor persistence, nor the fundamental nature of these ground plans has been explained or reduced to functionalist explanations. In the words of Gunter Wagner a leading authority in the field of evolutionary developmental biology: “there is still no explanation for the stability of the developmental type . . . [giving an explanation is] . . . the most urgent theoretical problem in the unification of development and evolution .” [my emphasis].