Ludwig von Bertalanffy's Organismic View on the Theory of Evolution (2024)

Abstract

Ludwig von Bertalanffy was a key figure in the advancement of theoretical biology. His early considerations already led him to recognize the necessity of considering the organism as a system, as an organization of parts and processes. He termed the resulting research program organismic biology, which he extended to all basic questions of biology and almost all areas of biology, hence also to the theory of evolution. This article begins by outlining the rather unknown (because often written in German) research of Bertalanffy in the field of theoretical biology. The basics of the organismic approach are then described. This is followed by Bertalanffy's considerations on the theory of evolution, in which he used methods from theoretical biology and then introduced his own, organismic, view on evolution, leading to the demand for finding laws of evolution. Finally, his view on the concept of hom*ology is presented. J. Exp. Zool. (Mol. Dev. Evol.) 324B: 77–90, 2015. © 2015 The Authors. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution published by Wiley Periodicals, Inc.

Ludwig von Bertalanffy (1901–1972) (Fig. 1) is widely known as the father of general system theory (GST). Some scholars are aware of his contributions to the concepts of open systems and steady state (flux equilibrium), and in some areas of research his growth equations are still being referred to today. Little, however, is known about Bertalanffy as one of the founding fathers of theoretical biology (Brauckmann, ²⁰⁰⁰; Pouvreau and Drack, ²⁰⁰⁷). He is also considered a forerunner of the organismic systems approach, which links his ideas to current evo-devo (Callebaut et al., ²⁰⁰⁷). Indeed, several issues that already concerned Bertalanffy are still being discussed today; and for many of them he provided new avenues of thinking. These issues include: evolutionary novelty, macroevolution beyond the explanatory framework of the modern synthesis, adaptationism, covariation, integration, and evolvability.

Gould and Lewontin (¹⁹⁷⁹) criticized the predominant “adaptationist programme” in evolutionary thinking in the United States and England, which was based mainly on natural selection and treated the organism as an aggregate or sum of characters that can be changed almost completely independently of each other. In contrast to that, they re-introduced organismic notions from continental Europe. Although they did not consider Bertalanffy specifically, the latter contributed considerably to the foundations of such a scientific treatment of integrated systems that went beyond more or less plausible adaptationist explanations and did not explain all characters as adaptation. He was even able to account for constraints due to system conditions.

Bertalanffy's thinking is therefore also relevant for current (evolutionary) systems biology (e.g., Soyer, ²⁰¹²) and related approaches (e.g., Winther, ²⁰⁰⁸). Very often only the GST book (Bertalanffy, 1969a) is referred to, leaving aside the substantial contributions that he made in biology while still in Europe. He started his career in Vienna and wrote his early works in German, which largely explains why they are not widely known.

This paper focuses on those rather unknown biological issues that Bertalanffy tackled. First, Bertalanffy's conception of theoretical biology is outlined. He was a key figure in establishing this discipline, which is meant to be useful for any biological question. It therefore needs to be discussed in some detail, also because it provides the logical and methodological basis for his critical approach to the prevalent theories of evolution. Theoretical biology is tightly related to the second part on the organismic approach or organismic biology. In this approach the system character of almost all biological entities is outlined. The approach that focuses on system features is again gaining momentum in current research (cf. complexity, network theory, etc.). Theoretical biology and the organismic approach form the basis of Bertalanffy's arguments regarding the theory of evolution—the third part. His critical investigations on theories of evolution—from Darwinism (here understood as Darwinism in the early 20th century, i.e., Darwin's account minus the inheritance of acquired characters) to the modern synthesis—are based on the methods that he developed in theoretical biology and the organismic approach. Lastly, the key concept of hom*ology—also as seen from the theoretical and organismic perspective—is described.

Those who are interested in the historical issues of Bertalanffy's life, e.g., his ambivalent connection to the Vienna Circle (Hofer, ¹⁹⁹⁶) are referred to the biography compiled by Pouvreau (²⁰⁰⁹). More about the many scholars who influenced Bertalanffy, from philosophy, biology, and other fields, can be found in Pouvreau (²⁰¹³).

THEORETICAL BIOLOGY

Theory in biology is not a modern invention, but can be traced back to ancient authors. Efforts to establish a field of research termed theoretical biology, however, only began some one hundred years ago. Authors such as Reinke (¹⁹⁰¹), Schaxel ('19), Uexküll ('20), Ehrenberg (¹⁹²³) used the term Theoretische Biologie (theoretical biology) explicitly, but with different aims. Often, theoretical biology was associated with philosophy of nature (Naturphilosophie), epistemology and metaphysics rather than with the formation of scientific hypotheses and theories. Reinke's work appears as a vitalistic philosophy of nature. Uexküll's theoretical biology is in large parts pure philosophy. Ehrenberg attempts to deduce the phenomena of life from the principle of the necessity of death. All these approaches have their merits, but only a few of them—Schaxel probably being a case in point (cf. Reiss, ²⁰⁰⁷)—are directly interesting for biology as a natural science (Bertalanffy, ¹⁹³²:3). Also Adolf Meyer-Abich's goal was to promote theoretical biology. For him, physical theory was a subset of biological theory (Meyer, ¹⁹³⁴; Amidon, ²⁰⁰⁸). This view, however, was not shared by Bertalanffy.

Following Ehrenberg, Bertalanffy distinguishes two related, and not strictly divided areas (significations, Sinn) of theoretical biology. (1) The first area deals with the epistemological and methodological basis of biology. This includes, on the one hand, the rational or logical analysis of the basis of knowledge in biology (e.g., the problem of teleology, or the relationship between experiment and theory) to avoid contradictions. On the other hand, it includes the critique of concepts and methods. For instance, the term mechanism (Mechanismus), with its several different meanings, is analyzed in detail with the result that it is too ambiguous a term to be used when exact concepts are required (Bertalanffy, ¹⁹³²:38ff,47; '37a:163f). The aim of such a procedure is a hypothesis-free and logically sound order of biological knowledge. (2) The second area is similar to that of physics, where the division between theoretical and experimental physics is well established (Bertalanffy, ¹⁹³²:6). This area is about the formulation of basic natural laws that can be tested experimentally (Bertalanffy, ^1930b:9). The descriptive biological facts have to be captured by overarching theories (Bertalanffy, ^1928c:51f).

The reason why investigations in the first area are necessary—while theoretical physics does not deal with such issues—is that theoretical biology is not yet a fully developed science. Hence, theoretical biology has to deal with tasks that physics no longer has to (Bertalanffy, ^1930b:11f). In physics, concepts such as force or energy are uses, and there is an agreement on how to use them. The question whether the explanations in biology can ultimately be reduced to concepts of physics and chemistry, however, cannot be decided yet, and appears to be rather unimportant (Bertalanffy, ^1930b:26). Clearly, certain phenomena in biology cannot be described solely with concepts from physics or chemistry because they are not tackled by the latter disciplines. Among such concepts are: organization, teleology, hierarchy, or type (Typus).

Within the second area, Bertalanffy distinguishes between (2a) bottom-up (von unten) and (2b) top-down (von oben) theoretical biology (Bertalanffy, ^1928c:58). (Note that this is unrelated with bottom-up and top-down in scientific explanations, where bottom-up refers to the level from the molecules upwards and top-down from higher levels, such as the organism, downwards.) The bottom-up approach consists of critically evaluating hypothesis and theories that were brought forward to explain certain phenomena of living organisms—demonstrating the valuable and discarding the useless. In research fields where almost all logically possible hypotheses were brought forward, it is reasonable to first analyze them before adding something new (Bertalanffy, ^1928c:100; '30b:11f). The result of such an endeavor is an order of facts and theories. A paradigmatic example for such a theory screening is Bertalanffy's investigation of theories of development (Bertalanffy, ^1928c:102ff). In that book—which was translated into English—he analyzes theories, spanning from crystal analogies to morphogenetic fields, and compares them logically and with regard to empirical evidence.

The top-down approach is characterized by deriving the single phenomena of life from a principle or theory (Bertalanffy, ^1930b:13). At the time, the prominent examples were mechanism and vitalism (Bertalanffy, ^1928c:100). Both, however, are problematic—a fact that Bertalanffy points out by means of logical and epistemological analysis (e.g., in Bertalanffy, ¹⁹³²:47ff). Being aware of such difficulties, he cautiously builds a deductive approach himself. In order to do so he provides a definition of the organism as follows: “A living organism is a system consisting of a large number of different parts, organized in hierarchic order, in which a large number of processes are ordered in such a way that, through their continuous interactions within wide borders, with a continuous change of substances and energies, the system stays, even when disturbed from outside, in its own state, or it builds up that state, or these processes lead to the generation of similar systems” (Bertalanffy, ¹⁹³²:83). The procedure would then be to deduce principles from the definition. By inserting specific conditions of certain phenomena into the definition, predictions can be made; these can then be compared to observations or experiments. This enables the theory to be tested (Bertalanffy, ¹⁹³²:119). This definition may not be exhaustive because it neglects, for instance, the historical character of life, but it serves as a starting point (Bertalanffy, ¹⁹³²:83ff; '52a:129). The organism-definition states the necessary and sufficient conditions for a natural object to be called living (Bertalanffy, ^1952a:130).

The greater aim of theoretical biology is to arrive at laws of nature (Bertalanffy, ^1928c:62,90ff). In this respect, theoretical physics serves as a role model. The exact details of the interplay between theories and laws are not provided by Bertalanffy, but he constantly refers to Viktor Kraft and his book on the basic forms of the scientific methods (Kraft, ¹⁹²⁶; Bertalanffy, ^1930b:12; '60:171). Important in this context is the difference between the hypothetico-deductive approach, which Bertalanffy strives for, and an inductive approach. To use a prominent example: the principles of mechanics, for instance of falling bodies without friction, cannot be inductively derived from empirical data (Bertalanffy, ^1927b:661). Such principles are no empirical sentences because they are based on conditions that cannot be found empirically (Kraft, ¹⁹²⁶:104). A similar logical character has to be achieved with laws in theoretical biology (Bertalanffy, ^1928b:8). Mathematics is, however, not the only basis for a strict theory. The same logical approach can be used when deducing from idealized conditions, or conditions that abstract from certain disturbances (Bertalanffy, ^1930b:12). The starting point is an intuitively derived hypothesis or theory. Empirical data can help on that path, but the aim is to deduce such data from the theory. The abundant amount of data has to be ordered by principles and laws; only then can one refer to this endeavor as science (Bertalanffy, ¹⁹³²:2f). Laws are deductively derived sentences that follow from theoretical preconditions, whereas rules are inductive generalizations of empirical facts which are not a result of logical necessity (Bertalanffy, ¹⁹³²:23).

To start with the aim to reduce the phenomena of the living to solely physics and chemistry would be a bias without any good reason and an unwarranted limitation. The peculiar features of living objects would then be at risk of being ignored (Bertalanffy, ^1928c:52f). Such fundamental biases determine what problems an investigator sees. They influence the framing of the questions, the experimental procedure, the methods, and the type of explanation and theory that are provided for the investigated phenomena. “In fact, the dependence on prevailing attitudes of mind is the stronger the less it is felt” (Bertalanffy, ^1952a:21). Bertalanffy points to an often false, or an outdated understanding of physics. Today, physicists abdicate causal explanations and rather search for connections between variables, from an initial to a final state. Similarly, with such an approach in biology one can also find regularities and hence laws, without the need to enter a meaningless debate on reductionism (Bertalanffy, ¹⁹³²:5,38ff,67). The function of a theory is to provide a common explanation for a number of otherwise unrelated facts. An explanation is defined as the logical subordination of the specific under a more general (Bertalanffy, ¹⁹³²:23f).

The knowledge about chemical reactions is necessary and important, but it does not answer the biological question of why this reaction occurs at this place and at this time in the organism and in general in a system-preserving manner (Bertalanffy, ¹⁹³²:25). This serves as an example for why considerations beyond an atomistic approach—i.e., a mental division of the organism into single, independent parts—are necessary. Apparently this biased atomistic view prevented the development of a theoretical biology (Bertalanffy, ^1930b:25f). The above argumentation makes it clear that a central issue of theoretical biology is the order or organization (Bertalanffy rarely distinguishes between the two terms) of the parts and processes in an organism. This problem was not tackled properly and therefore we lack theories and laws about it (Bertalanffy, ¹⁹³²:122). Wholeness (Ganzheit) is the prime feature of life and must therefore be investigated with scientific methods (Bertalanffy, ¹⁹⁴¹:250; '49a:119).

THE ORGANISMIC APPROACH

According to the analysis of Julius Schaxel—an important figure in establishing theoretical biology—the roots of the organismic approach can be traced back to Aristotle (Schaxel, ¹⁹²²:236). Bertalanffy used the term organismic biology to characterize his own fundamental conceptions, and strove to free them from metaphysical connotations in order to arrive at a science that takes the peculiar features of organisms into account. The time when Bertalanffy started to develop his organismic approach was characterized by an ongoing dispute between mechanists and vitalists. His organismic approach was meant as a way of research beyond those two approaches. Bertalanffy quotes Schaxel, who summarized the problems of a mere mechanistic approach as follows: “What legitimizes the mechanist to talk about adaptation and purposefulness, about individuality, about the whole and its parts, about the unit, organization, harmony, regulation, activity, autonomy, and finally about the organism itself?” (Schaxel, ¹⁹²²:158, cited in Bertalanffy, ^1927a:211)

Vitalists pointed to the problems of the mechanistic approach, and Bertalanffy acknowledges Hans Driesch for introducing the concept of wholeness (Ganzheit) into science (Bertalanffy, ^1928c:145). Wholeness stands in opposition to an atomistic approach with its predominant consideration of the parts. The experiments of Driesch on sea urchins—where he divided early stage embryos to yield single complete embryos—were crucial for this argument (cf. e.g., Driesch, ¹⁹⁰⁸:59ff). Furthermore, Driesch's critique (since 1893) of the mechanistic approach is seen by Bertalanffy as the most important because it is logically the most consistent (Bertalanffy, ^1952a:5). Hence, the neo-vitalists, like Driesch, were asking the important questions, but they only provided unsatisfactory answers, leaving the sphere of science to find themselves in metaphysical speculations.

The aim in Bertalanffy's organismic approach was to take the problems that were raised in that dispute seriously, but approach them with scientific means. Accordingly, organismic biology is a positivistic term and does not consider metaphysical concerns about a soul or entelechy (Bertalanffy, ^1927a:230).

Organism is a central concept (Urbegriff) that cannot and does not need to be dissolved or reduced (Bertalanffy, ^1928c:74). It is, however, important to arrive at a clear expression of this and other terms to make them operable (Bertalanffy, ^1928c:142). The phenomena of life are always connected to an individual organism. A summative approach is therefore insufficient. Regulation is a striking example for this argument because it not only depends on the single parts, but also on the condition of the organism as a whole (Bertalanffy, ^1929c:381f). Other phenomena such as metabolism, excitability, reproduction, or morphogenesis also cannot be explained sufficiently solely with analytic sciences (Bertalanffy, ^1929b:391).

The organismic approach is a research program, a basis for proposing new questions, without providing any premature explanations—such as found in mechanicism and vitalism (Bertalanffy, ¹⁹³²:V; '51a:8). In so proceeding, Bertalanffy is not dogmatic and also points to the merits of mechanistic or reductionistic explanations in cases where they appear to be appropriate. The starting point is not an either holistic or atomistic attitude, but rather facing the problem to then decide which approach can be used. In this manner the holistic or organismic approach is a working hypothesis with the aim of raising concrete questions and searching for solutions (Bertalanffy, ^1937c:9; '52a:181). A one-sidedness in either direction has to be avoided, an attitude that Bertalanffy underlines when using a statement of Johann Wolfgang von Goethe as leitmotif: In looking at nature one has to pay attention to the one and the whole (Müsset im Naturbetrachten immer eins wie alles achten) (Bertalanffy, ¹⁹³²:III).

In presenting general system theory, Bertalanffy provides an example to illustrate his approach that also holds for biology. When considering a set of parts, where each is connected to each other, all changes in one part affect the others. This system can develop differently. It is for instance conceivable that over time the interactions between certain parts become weaker or non-existent. In such a case isolated areas can appear that have only minor or even linear causal dependence of one part on the others. This is termed mechanization or progressive segregation (Bertalanffy, ^1969aa:66ff). When applying this thought model to a developing embryo, for example, a primary connected system can be imagined that, as it grows, can segregate into different more or less independent regions. Hence, it is unsurprising that some sort of “mechanized” behavior can be found. This, however, is only one extreme of what is possible in the range from a completely connected system to isolated parts. Even though the organismic approach allows for different perspectives, for Bertalanffy the system is primary and mechanization secondary (Bertalanffy, ¹⁹³²:99).

The central problem that Bertalanffy sees in (theoretical) biology is the organization of the parts and processes in such a way that they sustain the living whole, the organism. Knowing the single parts and processes in the finest detail that physics and chemistry provide—which is necessary—is, however, insufficient to explain their organization (Bertalanffy, ¹⁹³²:VII,52; '37c:8; '52a:11,182). The laws for chemical reactions, for instance, are in principle insufficient to explain organized forms (Gebilde) (Bertalanffy, ¹⁹³²:324; '52a:62). Thus, it is impossible to conclude a (vectorial) 3D form solely from scalar quantities, such as concentrations. The organization of all the physico-chemical processes is what distinguishes the living from the dead (Bertalanffy, ¹⁹³⁴:347; '52a:13). The challenge that also arises here is that the whole organism shows properties that are absent in the isolated parts. As long as individual phenomena are investigated in isolation, no fundamental difference between the living and the non-living, and thereby no primary feature of life, will be found (Bertalanffy, ^1952a:12). More recently, in the same line, Lewontin (²⁰⁰⁰) acknowledged that we cannot escape what he calls the dialectic between part and whole in biology.

There is a difference between summative and constitutive properties that should be noted. An example for a summative property is mass. Knowing the mass of part A and part B, one can easily calculate the mass of the two together. An example for constitutive properties are the chemical properties of isomers that consist of the same atoms. In this case it is necessary to know the arrangement of the atoms to potentially derive the properties of the molecule (Bertalanffy, ¹⁹⁴⁵:6). An organism has many constitutive properties. Recent accounts still revolve around such ideas on emergence (e.g., Wimsatt, ²⁰⁰⁷:277–287), but hardly refer to the earlier thinker.

The teleological aspect of the central problem is evident in terms such as organ, function, organism, or pathology. This raises the question of the importance of each part or process for the preservation of the organism (Bertalanffy, ^1929b:388; '30a:64). Furthermore, terms such as adaptation, regulation, regeneration, norm, or perturbation signify the preservation of a system state (Systemzustand) which we call life (Bertalanffy, ^1929b:388). Two notes are necessary here. First, teleology was annotated with several different meanings, from an anthropomorphic psychic capacity of anticipating a goal and behavior to achieve this goal, to a “reverse” causal connection from a future state to a present state. Both these meanings are not applicable in biology. Second, Bertalanffy distinguishes different stages in biology. Broadly, there is a descriptive and an explanatory stage (Bertalanffy, ¹⁹³²:9ff). Description is more important in biology than in other sciences due to the vast amount of different phenomena that have to be surveyed and ordered. In this stage, teleology plays a role because it is a true gain of knowledge when finding out what a sense organ or a thorn is good for (Bertalanffy, ^1927a:235f; '28c:77). In the explanatory stage, however, teleology must not appear. How the single parts and processes are ordered to guarantee the preservation of the organism has to be causally explained (Bertalanffy, ^1929b:384). Here he closely follows the clarification of Emil Ungerer—a botanist and philosopher of biology, who also published in Schaxel's book series on theoretical biology—on the “real contemplation of fitness (echte Zweckbetrachung)” and “preservation of the whole (Ganzheitserhaltung).” The organism and the processes in it seem to behave “as if” it was after some aim (Ungerer, ¹⁹²²; Bertalanffy, ^1930a:64; '32:17f, cf. also Kant, ²⁰¹⁰:§68, Vaihinger, ¹⁹⁶⁵). Seemingly teleological behavior then is a result of system laws. Bertalanffy suspects that the causal inner dynamic in the system as a whole approaches an equilibrium, which appears as if it were purposeful (Bertalanffy, ^1930b:22; '32:13).

Parts can behave differently in isolation compared to parts in connection (Bertalanffy, ¹⁹⁵⁷:8). This entails an epistemological problem. To know the behavior of one part, one would need to know the behavior of all the interactions it depends upon. This, however, leads in a circle because the same argument holds for all the behaviors of the other parts as well. The single processes in a system, therefore, can only be determined approximately. One way to handle this problem is to look for laws of the overall behavior (Integralgesetze) of the system without considering the single parts and processes (Bertalanffy, ¹⁹³²:110). The laws of thermodynamics serve as a role model. Bertalanffy's growth equations are an example that such an approach is also advantageous in biology. In those equations, assimilation and dissimilation are connected to growth in a physiologically meaningful manner (for details see Pouvreau and Drack, ²⁰⁰⁷).

The dynamic character of biological systems is an issue that Bertalanffy underlines in the interaction among parts and processes, but also in the open system property of life: the constant replacement of all the parts while, as a whole, the organism remains relatively constant (Bertalanffy, ¹⁹³²:116). This principle was already anticipated by Heracl*tus and by Johannes Müller (Bertalanffy, ^1937b:107). The dynamic equilibrium in an open system is different from the equilibrium in a closed system where no work can be done. Bertalanffy worked intensively on this issue and coined the term Fließgleichgewicht (steady state) (e.g., Bertalanffy, ¹⁹⁵⁰; '53). The open system feature is a necessary condition for all life (for more details refer to Pouvreau and Drack, ²⁰⁰⁷; for the homeostatic properties of species see Rieppel, ²⁰⁰⁹).

Another important feature is the hierarchical order in living systems, which is connected to the principle of open systems. What in one system is an irreversible process (formation, aging, and death) can be viewed in the next higher level as a phase within a repeated dynamic (Bertalanffy, ¹⁹³²:204). Everything is considered as dynamic. Structures which seem to be stable on one time scale appear as slow processes and functions as fast processes (Bertalanffy, ¹⁹³²:249). This view also entails what Bertalanffy calls a dynamic morphology: it goes beyond a static description and connects the change of form with physiological processes. The task is to derive organic forms from the ordered play of “forces” that can be captured by quantitative laws (Bertalanffy, ¹⁹⁵⁰:27; '52a:136). The hierarchy of processes reflects one particular meaning of the term hierarchy. In fulfilling his proposal of theoretical biology, Bertalanffy—based on Joseph H. Woodger—analyzed seven different meanings of this problematic term (Bertalanffy, ^1952a:37ff). Hierarchy is apparently also present in the genome, and Bertalanffy points to a “rank-order of the genes, from genes that control single, often minute, characteristics to those that influence a larger number of characters in more or less extensive pleiotropism […], and finally to ‘superordinate' or ‘collective' genes (E. Fischer, Pfaundler) that direct the activity of numerous other genes” (Bertalanffy, ^1952a:47). Considering hierarchies is also important because the state of a part can depend on the condition of higher levels or the organism; the performance of the parts is connected to the organism as a whole (Bertalanffy, ¹⁹³⁴:347; '51b:231). This requires investigating all levels of organization. Research on one level cannot replace research on the higher levels (Bertalanffy, ¹⁹³²:113). This view is also shared by recent researchers and is considered again as being important (cf. e.g., Noble, ²⁰⁰⁶). Note also that the analysis of the concept of hierarchy—division hierarchy in particular—by Woodger was transmitted via Bertalanffy to Willi Hennig. For Hennig's phylogenetic systematics this played an important role (Hennig, ¹⁹⁷⁹:21, Rieppel, ²⁰⁰³)

The intrinsic or inner dynamics of “forces” within a system, rather than fixed structures, have to be investigated as the basis for the harmony and coordination of the processes (Bertalanffy, ^1933b:258f). The inner condition or system conditions, the causal interconnections, are more important for an organism's performance than non-disruptive interaction with the environment. An organism's autonomy is based on the system conditions (Bertalanffy, '30/'31:394). The autonomy or activity of an organism is very important for Bertalanffy, and distinguishes his point of view from the conception of the organism as a reactive, stimulus-response machine driven solely by outside factors. This point is relevant not only for behavior and psychology (cf. Bertalanffy, ^1929b), but also for his view on evolution, as discussed below.

Bertalanffy summarizes the leading principles of the organismic conception as follows: “The conception of the system as a whole as opposed to the analytical and summative points of view; the dynamic conception as opposed to the static and machine-theoretical conceptions; the consideration of the organism as a primary activity as opposed to the conception of its primary reactivity” (Bertalanffy, ^1952a:18f). The attempt to overcome the mechanistic and vitalistic approaches yields the research program of an organismic biology, whereas the attempt to explain life is termed the system theory of life (Bertalanffy, ¹⁹³²:80).

EVOLUTION VIEWED FROM THEORETICAL BIOLOGY AND THE ORGANISMIC STANDPOINT

As a central theme, for Bertalanffy the organismic approach is relevant for all areas of biology, hence also for the theory of evolution. Even though he himself did not conduct deep research in this field, he arrived at theoretical and conceptual considerations of evolution which are hardly known today. His writings on evolution from the 1920s to the end of his life reflect his approach to theoretical biology: initiate with a critical investigation, then contribute to further scientific developments. Accordingly, the following discussion first points to his critique and then shows how Bertalanffy introduced the organismic approach to the theory of evolution.

hom*oLOGY

Unsurprisingly, Bertalanffy also applied his methods in theoretical biology to a central concept of evolutionary thought: hom*ology. The historical and theoretical clarification of such terms is an important task within theoretical biology. Hence, Bertalanffy used this method in various fields and for various central concepts, even though they belonged to areas—such as evolution—that were not his primary focus. He wanted to show, however, that his organismic or system approach is useful for any biological area. He starts by analyzing the ideas brought forward so far and then introduces his own, organismic view on the concept of hom*ology. He did this in depth in only one German article that appeared in a less well known journal (Bertalanffy, ¹⁹³⁶; nonetheless, a translation was published posthumously: Bertalanffy, '75) and is interesting for evo-devo and evolutionary systems biology. Most of the following is taken from that '36 article.

Bertalanffy starts his analysis with the problems that the founding fathers of morphology—Goethe and Étienne Geoffroy Saint-Hilaire—addressed. In Goethe's morphology the single forms of organisms appear as different embodiments of an ideal type (Typus). This calls for clarifying the meaning of the often misunderstood term type. Type refers to an ideal image (Urbild) of different forms that never existed, not to be confused with ancestor organisms that really existed. The term, however, is not a mere product of fantasy. In modern terms, type would refer to a composition or organization law (Aufbaugesetz) of a group of entities similar to a general structural formula in chemistry. In this sense, a type or a general structural formula cannot be directly observed, but they are not “unreal” either. Hence, the term type can be used without any connotations of an idealistic Platonism. Logically, it has an equal status and is equally “real” as a law of nature: both are mental constructs and cannot be directly observed in nature. From a certain perspective the concept of type belongs to the descriptive stage, without any claim of explanation (cf. the stages of biology above). For an explanation, however, the governing laws have to be found (Bertalanffy, ^1949b:80ff).

Throughout the course of history, Bertalanffy identifies three successive definitions of the hom*ology concept. The first is what he terms the typological concept of hom*ology (typologischer hom*ologiebegriff), which refers to Richard Owen: hom*ologous organs correspond to each other according to their location, irrespective of different functions. They are at the same position with respect to neighbor organs.

This is followed, second, by what slightly misleadingly is called the typologico-evolutionary concept of hom*ology (typologisch-entwicklungsgeschichtlicher hom*ologiebegriff); typologico-developmental hom*ology would be a more appropriate term: hom*ologous are those organs that develop from equal embryonic primordia (Anlagen); such a view was already present in Karl Ernst von Baer's thinking (Brigandt, ²⁰¹¹). This refers to the investigations of Karl B. Reichert on the development of the bones in the inner ear. Even though in adult individuals a hom*ology based on neighboring parts is no longer valid, it still holds for the primordia. The typological concept is still basic.

The first two concepts were developed before the doctrine of descent (Darwin) was introduced. The theory of evolution consequently lead to the third concept, the phylogenetic concept of hom*ology: hom*ologous are those organs that phylogenetically originate from each other or from a common ancestor. While some welcomed the new concept, not everyone was convinced and some challenged the autonomous value of this concept of hom*ology. The phylogenetic concept did not replace the typological concept. Rather the typological concept—be it about the locations of organs in adult or embryonic primordia—constitutes an important criterion for the phylogenetic concept of hom*ology. The view that hom*ology has its value independent of evolutionary interpretation was broadly acknowledged by evolutionary morphologists (Russell, ¹⁹¹⁶:355, Brigandt, ²⁰¹¹). Location is directly observable, descent is not. Morphology thus appears as one basis for finding evolutionary explanations. The debate whether morphology should be conducted without considering phylogeny or not continued into the 20th century; cf. e.g., the different views of Adolf Naef, Willi Hennig, and others (Rieppel, ^{2006, 2012}; see also Schindewolf, ¹⁹²⁸ for the relationship of systematics and phylogeny). Note, however, that Bertalanffy perceives morphology as one means amongst others to clarify the course of evolution. Morphology includes no time dimension, whereas other aspects, such as stratigraphy, do. Hence, “not only does the typological hom*ologization serve as the base for the phylogenetic derivation, but vice versa, the morphological clarification of uncertain elements is often possible only by means of a phylogenetic analysis” (Bertalanffy, '75:91). This is a typical instantiation of Bertalanffy's perspectivist epistemology (Pouvreau and Drack, ²⁰⁰⁷:289ff).

The concept of hom*ology was also challenged by developmental biologists. The regeneration of the eye lens, after operational removal, shows that it does not develop from the epidermis, as in normal development, but from the side of the iris. What does that mean for the (second) concept of hom*ology? From equal material, different organ parts can develop, and different material can develop into equal parts, such as a lens. For Hans Spemann (¹⁹¹⁵)—who is well known for his transplantation experiments and the conception of embryonic induction by organizers—the hom*ology concept seemed to dissolve (cf. Laubichler, ²⁰⁰⁰). Also Gavin Rylands de Beer, who was the first to note that the sameness of genes and sameness of morphological structures do not map, criticized the traditional embryological criterion of hom*ology (Brigandt, ²⁰⁰⁶). For Bertalanffy, however, the difficulties arise from preconceived opinions, and he asks for a new conception because, in normal development, such artificial experiments do not occur.

The old hom*ology concepts were preformistic to Bertalanffy. Underlying these concepts is the idea that certain primordia for certain formations are already there in the beginning. Developmental biology, however, shows a non-preformistic and epigenetic character. Epigenesis refers to the interaction of the parts in the whole system (Bertalanffy, ^1937c:107). What is fixed at the beginning is not the material primordia of the single organs, but rather the organizational relationships that brings forth a species-specific organism. Within the organizational relationships the formation of the lens is bound to a specific location and is independent of the material. The hom*ology concept can thus be maintained if the essential factor is not the material from which a particular organ is formed, but rather the organizing relations. The old concept of hom*ology of equal locations still holds if, by “location,” a dynamically effective factor rather than a reference to geometric site is meant.

Bertalanffy therefore defines a developmental physiology (entwicklungsphysiologisch) or dynamic concept of hom*ology: hom*ologous are those organs that developed in equal location, i.e., under according organizational relationships; or: “organs which occupy the same position in the organizational set of relations” (Bertalanffy '75:95). Equal location remains basic, yet no longer in the sense of an ideal relationship but rather in a “real” organizational causal relationship. Not the static form is essential, but rather the site of certain system conditions. This concept of hom*ology reflects the fact that organic form can only be conceived of as being dynamic. Even though Bertalanffy provides no more than a sketch of a new hom*ology concept, it is related to modern, more detailed accounts that investigate the causal basis of hom*ology (Wagner, ¹⁹⁸⁹; 2014).

Note that one critique of Bertalanffy's analysis of the hom*ology concept came from Adolf Remane. To clarify the theoretical foundations of phylogeny and systematics, the latter sought an understanding of the principles of comparative anatomy and, hence, an operational account of the hom*ology concept (Laubichler, ²⁰⁰⁰; Brigandt, ²⁰⁰⁶). Just before Remane describes his well-known criteria of hom*ology, he notes that since there is only one natural system (natürliches System) there can only be one concept of hom*ology. The different concepts of hom*ology, as described by Bertalanffy, would rather refer to partial criteria of a single concept of hom*ology (Remane, ¹⁹⁵²:32f). That critique is not well justified. Remane himself points out that the concept was gradually developed. Importantly, Bertalanffy provides precisely this overview and analysis of the meaning different authors gave to the term throughout history, and holds that location is the most important criterion (Bertalanffy, ^1937c:166). Importantly, Bertalanffy was interested in the causal basis of hom*ology and not so much in operational criteria for distinguishing between hom*ologies and non-hom*ologies.

Bertalanffy's new conception of hom*ology is a typical example of how he used the dynamic systems or organismic approach to reinterpret established facts and therewith made progress in uniting knowledge form different threads of research.

CONCLUSION

Bertalanffy's approach can be seen as opening the field of potential explanations. He articulates the basic problems of biology and relates them to potential explanatory pathways. The general phenomena of life are connected to the organization of the parts and processes within an organism. Considering the regularities in such system behaviors prompts Bertalanffy to propose research designed to discover the laws that govern them. The organismic approach is—without neglecting the merits of purely analytical endeavors—important for all fields of biology, and hence also for evolutionary biology and even the concept of hom*ology.

Bertalanffy had an effect on many researchers in different fields, but probably only a few evolutionary biologists were directly influenced by him. One of his students was Rupert Riedl, who is also prominently quoted by Gould and Lewontin (¹⁹⁷⁹). The influence of organismic biology or the system theoretic approach is clearly evident in Riedl's work (Riedl, ^{1977, 2000}). Based on system thinking, Riedl derived a theory that reduces the role of chance in evolution and hence the role of mere adaptation, leading to the notion of burdens that constrain the course of evolution.

To summarize Bertalanffy's approach, one could alter a famous statement by Dobzhansky (¹⁹⁷³) and say: Nothing in biology makes sense except in the light of organization. This is true even for evolution.

Acknowledgments

I am much obliged to Günter Wagner for the kind invitation to write this article. Thanks go to Ingo Brigandt and two anonymous referees for very useful suggestions on the text. The research of MD was funded by the Austrian Science Fund (FWF): P22955-G17.

LITERATURE CITED