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By Alex Brown



This paper proposes the application of evolutionary theory to the analysis of architecture defined here as a complex adaptive system. Through a comparison of terms, processes and mechanisms, the paper seeks to identify the analogies between architectural and biological systems. The intention here is to establish a theory of evolutionary change in architecture which can explain the formation, development, eventual extinction of architectural styles throughout history. These large scale changes in architecture can only be understood by recourse to a general theory of adaptive change similar to that currently employed in the biological sciences. The aim here is ultimately to eliminate the individualistic and subjective explanations offered by current architectural history and theory in favour of a more rational and coherent theory of large scale systematic transformations.


1.     Initial Definitions




A cultural system which adapts its forms to represent relationships between the elements of its environment.  Architecture is information which characterizes the forms of buildings which themselves are simply material objects.




Continuous adaptive change by a system in response to conditions imposed by its environment.

 Environment:  A group of systems in constant communication with one another each of which attempts to adapt its behaviour to the state of all the others.




A community of organisms defined by a reproductive boundary within which genetic information is exchanged leading to a similarity of physical characteristics within the community.




A group of buildings which use the same set of typical elements leading to a similarity of architectural characteristics within the group.


Natural Selection: 


The mechanism by which the particular characteristics of organisms are tested against the prevailing environmental conditions and some are eliminated. The success or failure of the individual organisms of a species to cope with the conditions of their environment determines their relative reproductive success.




The characteristics and organization of a system are a function of the interlocking activities of its agents. The key activity being the communication and exchange of information between them.



2.     A Brief Outline of the Theory of Evolution 


The Theory of Evolution as it currently stands is a based on the work of two men: the British scientist Charles Darwin and his 19th century contemporary, the Austrian Gregor Mendel.  While Darwin’s achievement was to define the mechanism of evolution, namely natural selection, he could not at that time specify the means by which the successful characteristics of one generation could be passed to the next. It took the work of Gregor Mendel, to identify the gene as the unit of inheritance. However, it was not until the 1940s that these two ideas could be successfully united in a single evolutionary theory – the ‘new synthesis’. It is this that now stands as the orthodox approach to evolutionary biology.At the core of the theory of evolution lie the same few principles which can be stated simply as follows: that any evolutionary system should display:




Where a system can generate a range of different behaviours in response to different environmental conditions.




A mechanism that allows the system to ‘remember’ which options are appropriate to given environmental conditions and can pass them on to new generations. In biological systems the DNA molecule performs this function.




Where the genetic characteristics of two organisms are combined to produce a new organism. More generally, the production of new forms of behaviour by the communication and exchange of information between the agents of a system. In order to survive, organisms must adapt to conditions which prevail in their environment. The ability to adapt successfully is a function of the genetic make-up which defines the physical characteristics and behaviour (the phenotype) of the organisms. However, this genetic composition varies from individual to individual of the same species. This produces a difference in the ability of individual organisms to adapt successfully to their environment by acquiring the necessary resources for survival. The filtering of successful and unsuccessful characteristics is called natural selection. Organisms which display successful adaptations will survive to produce more offspring than unsuccessful variations. Their offspring will, with minor variations inherit the genetic combination of their parents. While organisms die, their genetic memory lives on in their offspring and that memory provides instructions to future organisms about the adaptations necessary for survival. The organisms having these successful traits will grow in numbers. Continuous adaptation to meet new environmental circumstances produces continuous and gradual phenotypic change (in body form and behavioural characteristics) in the organisms of a species up to the point where they are recognizably different from their ‘original’ or ancestral form. At this notional point in time, a new species is said to have emerged.


3.      Evolution as a General Theory of Change


The idea of evolution is now no longer particular to the biological sciences or to any other field for that matter, even though since Darwin its most advanced development has taken place there. The reason is that evolutionary theory has become a much more broad-based set of disciplines that deal essentially with the mechanisms that produce change or, more precisely, transformation in the characteristics of dynamic or adaptive systems in general. In other words we are no longer simply talking about biological species but, rather about organizations or systems which can be said to adapt to their environments. That obviously includes all social and biological systems. It is the cumulative effects of this dynamic system-environment relationship which have become the object of study and simulation within the general field of evolutionary theory. Effects which over long periods of time alter the characteristics of the systems involved and in an evolutionary process transform them into new kinds of systems.


4.       Adaptive systems


As a primary definition of adaptive systems one can say that they are organized groups of agents or organisms which modify their behaviour to match conditions prevalent in their environment. When viewed as adaptive systems there are major similarities of process between biological and cultural systems. Architecture is a cultural system. The only difference is that of the specific medium of exchange used within each system. In biological systems that medium is the genetic material which is exchanged between the individual organisms of a species-system usually through sexual reproduction. In cultural systems it is experience or forms of behaviour  which are exchanged between the agents of the system. However even this difference between biological and cultural systems can be subsumed under the general category of ‘information’ created by agents or organisms interacting with their environment. This is exchanged within the system by communication and written out or materialized in the form of a new generation of individual organisms, types of social behaviour or architectures. The evolution of adaptive systems whether biological or cultural is thus an active product of collective behaviour – the continuous construction of ever-new models of the environment.


5.       Translation of Concepts from Biology to Architecture


In translating this theory from the biological sciences into architectural terms, one must ensure that the comparisons made are consistent both in terms of the mechanisms involved and the organisational levels being discussed. Equivalence of processes and terms can only be established by comparing like with like. For instance, clearly there is no similarity between a building and a living organism. However, if we view them both as the product of communication and exchange processes within their respective systems, as specific attempts by those systems to adapt to local environments and as the basic units of selection within their systems, their equivalence to each another becomes less strange. In other words, while they are not similar to one another, they are ANALOGOUS in terms of their origin, function and hierarchial position in their respective systems. It is on this basis that the concepts and terms of evolutionary theory can be applied to architecture in an appropriate and useful manner.


6.     Equivalence of Terms and Concepts between Architecture and  Biological  Systems.


Based on the ideas outlined above we can make the following possible equivalences:


a)    ‘Representation’ as a Concept in Architecture is Equivalent to the  biological Concept of  'adaptation’.


In a very real sense, architecture as system REPRESENTS its environment. Buildings are produced by mapping the form of a referent institution into a set of architectural elements. These elements are adapted to match the functional and organizational state of the institution which is the ‘environment’ of the building. They are attempts to model those environments and give them a physical presence in space and time. This environment includes the context of the institution, its location at a particular place and time and the financial and technological constraints which operate there. In both architecture and biology a given set of elements (of form, behaviour or genetic information) are combined to match the organizational state of an environment. In one case the result is buildings, in the other the result is organisms. In both cases one can think of this as a transcription process or in a more literary sense the making of a metaphor. The organization of one system (an environment) is written out or translated into the form of another (the system). When a system adapts, it characterizes or represents its environment in the form of its own behaviour. The form of a system is a map of its environment.


b)    The Architectural Concept ‘style’ is Equivalent to the Biological Concept  ‘species’


An architectural style is not a homogenous entity but a statistical one defining a range of formal characteristics shared to some extent by a large number of buildings. The similarity between these buildings is a product of communication and exchange of experience between many architects. This is quite consistent with the biological communication of genetic information during reproduction. In biology for instance, the definition of species is that of a ‘reproductive community’. That is, a group of organisms who are able to interbreed with one another and thus share genetic and physiological characteristics. As pools of information derived from past experience, both the style and the species act as sets of instructions (iconic and genetic) which define the general characteristics of buildings and organisms respectively. Differences between individuals within these groups are a product of the variety produced by modifying these general or generic forms to fit many different environments.


c)    The Typical Elements of a Style are Equivalent to the Genetic Complement of a Species.


Both Provide the Heredity Mechanism Necessary for a Evolutionary System. In architecture, the generic set of typical elements filtered out of past experience can be described as the language of architecture which provides a set of options for modelling future environments. In this it acts very much like the genetic pool of a species which, as a repertoire of possible biological characteristics encoded in the DNA molecule may be combined for potential organisms. In both cases these sets of instructions provide the memory of the successes and failures of the system’s many previous interactions with its environment. These are filtered by natural selection and exchanged and combined within each system into a set of fundamental elements applicable to future encounters.


d)     Buildings in Architecture are Equivalent to Organisms in  Biological  Systems.


The individual organism is the unit of selection for the biological species. The individual building is the unit of selection for architecture. In both cases it is these units that are adapted more or less successfully to their local environments. They are both products of exchange processes taking place within their systems. They are both unique combinations of a generic set of elements to be found in their respective systems. In one case a set of typical architectural elements, in another a set of genetic elements (the genes). Both the building as a particular combination of elements and the organism are both subject to natural selection. That is, they are tested in terms of their success at adapting to their environment. If successful their particular combination of elements will be reproduced in future combinations. In architecture that means that the particular set of forms will become an imitative source for future buildings. 


Finally, we can say that: Organism is to Species as Building is to Style.


(Note: We must make a clear distinction here between architecture and buildings. Buildings are material objects while architecture is the information which gives these objects a particular shape or character.


e)    Cultural Environments are analogous to Biological Environments


The environment of a cultural or biological system can be seen as a group of systems in constant communication with one another each of which attempts to adapt its behaviour to the state of all the others. The environment is not a thing but an event and a collective term for a group of interacting systems. That event is the mutual adaptation brought about by communication between those systems. Described in ecological terms, it is made up of a group of niches within which conditions are more or less stable. Cultural environments can be defined as a group of interacting institutions. Biological environments are a group of interacting species together with the climatic and geological contexts within which they act.


f) Communication and exchange Processes in Architecture are Equivalent to Reproductive Processes in Biological Systems.


New organisms are produced by combining the genetic complement of a previous generation of organisms. New buildings are produced by combining the typical set of a previous generation. of buildings. In both cases what is being exchanged and combined is the concrete experience of particular organisms or buildings in particular environments in the past. That is, their success or failure in coping with the conditions of its local environment. It is this that is communicated to the next generation. Neither individual buildings nor organisms are copied into the next generation. Their particular successful combinations are exchanged with all others to provide a generally available repertoire of possible combinations that can be applied in many different environments. This is the typical set of an architecture (a style) or the genetic set of a species (the genome) and is the result of multiple exchanges (of information about past experience) between the agents of each system. While sexual reproduction involves the random exchange of genetic information from two organisms to form a third, architectural exchanges involve the exchange of iconic or semiotic information from many different agents. In both cases the resulting form is unique in its characteristics while remaining recognizably within the limits of its generic set – the particular style or the particular species. The basis of architectural exchange is selection of forms from the repertoire and their combination for a particular environment.


g)    Variety in Biological Systems Corresponds to the Production of  Differences in Architecture.


The random process of biological reproduction produces unique individual organisms. The exact genetic combination of the organism cannot be predicted since the particular combination of parents, the genetic shuffling of genes during reproduction and the effect of chance mutations is quite random. The only predictable thing about this process is that it will take place within the gene pool of a particular species. The result is that a variety of genetic traits is continually produced within the species leading to new and potentially viable characteristics. In a similar way each building is unique formed as it is from combining typical forms in many different kinds of buildings whose exact context (size, location, finance, technology, cultural significance) cannot be known beforehand. Equally, the character of the typical set of a style cannot be predicted since it keeps changing as new buildings are built and their experience is incorporated into it. The result in both cases is the continual production of variety in the system whether biological or architectural.


h)    Natural Selection in Biological Systems is Analogous to  Semiotic Selection in Architecture.


Natural Selection in biological systems is based on an organism’s ‘economic’ success in acquiring enough resources for its survival up to the point of its natural lifespan. This is depends on the organism’s adaptive flexibility in its environment. Particular character traits in organisms are selected on the basis that they can deliver the economic resources needed to survive and thus reproduce. Failure to do so means that a particular organism’s genetic combination will not be transmitted to the next generation. ‘Success’ in biological terms is therefore about adaptive flexibility: the capacity to adequately represent its environment in the shape of its own behaviour. The same criteria applies to architectural works. The success or failure of a particular building is a matter of how well it represents its local environment with the set of elements at its disposal. This is essentially a semiotic issue, namely the manipulation of iconic signs to produce a precise metaphor of a particular institution and its context.


Since each building once built becomes an imitative source for many other buildings, its semiotic success or failure determine the degree to which its particular combination is repeated and exchanged in the selection and combination process carried out between many architects.


i)      Emergence of a Style in Architecture Corresponds to the  Formation of a Species in Biological Systems.


Species emerge from other species by three possible processes:


i.    Within a species, a continual process of adaptation to changing environmental circumstances. The cumulative effect of these changes in form and behaviour  over long periods of time result in the production of a new species.  


ii.        When a part of a species invades and occupies a new habitat and over time and under natural selection forms a reproductive barrier between itself and its ancestral population, effectively becoming another species.


iii        It may also be that a chance genetic mutation in a parent species if successful and allowed to reproduce, causes a part of the population to develop a distinct genetic set sealing it off from reproduction with the parent species.


The same possibilities occur in architecture, where:


i.        The continuous incorporation of many different individual works into the typical set of a style by  architects results in time in the emergence of what is effectively a new style radically different in form from its origins.


ii         The collapse of an imperial society effectively isolates groups of architects from communication with all others. This produces increasingly regional variations on the original stylistic theme to the point where they no longer can be seen as part of the same style.


iii        Occasionally completely new architectural forms will be produced by architects which are  unpredictable as legitimate combinations of the prevailing typical set. In diverse or plural cultural environments these unconventional forms may, given enough time, establish  themselves as coherent alternative styles.  


j) Extinction of a Species in Biological Systems Corresponds to the Collapse of an Architectural Style.


A species becomes extinct when its members can no longer reproduce enough new organisms to replace the natural death rate of the species. This may happen for instance if catastrophic environmental changes prevent the organisms from adapting to radically new circumstances. They may not have the built-in adaptive flexibility to handle such changes. Their genetically -programmed behaviour drawn from past experience prevents them from acquiring the resources necessary for survival. Thus they cannot reproduce enough new members to replace those who die off. In architecture a style may be said to become extinct when architects no longer use its typical set to produce new buildings. This may happen for two main reasons:


i.        Changing environmental conditions – the unpredictable arrival of a whole new and diverse system of patronage dissolves the prevailing stylistic consensus amongst architects. The new plurality of commissioning sources provides new environmental niches. These encourage or require architects to produce unconventional combinations of forms relative to the dominant typical set. The new diversity of the cultural environment destroys the former connectivity and communication between architects resulting in a collapse of the dominant style which is either marginalized or falls into disuse. There are too many new ways of doing the same thing. 


ii         Over a long time and in an ultra-stable environment the typical set of a dominant style becomes stereotyped and very specialized in the way it allows architects to combine its forms. This is due entirely to the normal processes of communication and exchange between architects taking place in a rigidly coordinated environment. The result however, is that they are less and less able to freely adapt the forms of the typical set to suit different environments. They can no longer express the difference between different institutions. The result is the collapse of meaning in architecture.


k)  Self-organization as the Basis for the Origin of Biological and Architectural systems.


In biological systems an initially chaotic lifeless state is resolved with a change in environmental conditions towards a stable state. Over time and in a process of trial and error chemical reactions are now allowed to form self-replicating molecules which act as a platform for the establishment of life. If, architecture is defined as a relation of similarity between a number of buildings, then at some notional point in the past one could imagine a situation where there was no such similarity and therefore that architecture did not exist. What would exist is a collection of very differently characterized buildings. For architecture to emerge requires a change in environmental circumstances. A shift towards a more coordinated, defined and stable environment. The architects who practice within this definite frame can now exchange information from each other by selecting forms from other architects work and thus increasing the similarity between those works. In doing so a common language of architecture emerges for the most unintentional and economic of reasons. This common language is an architectural style which produces a broad similarity of characteristics among the buildings within that environment. Architecture now exists.


7.        Conclusion


Given the complex interaction between the social, cultural, geographical, technological, economic factors and the myriad individual intentions which together provide the frame for architectural activity at any point in time, one is faced with this question. How is it that any coherent stylistic order could arise out of this matrix of forces at all? Here we have a phenomenon which in the midst of all the competing forces mentioned above, unifies the characteristics of the buildings produced during each historical period from the scale of their overall form to their decorative detail. The form of thousands of individual buildings built in many different places and constrained by different technological, economic and institutional demands are coordinated by a single stylistic template into a unified physical environment. Here in the phenomenon of the style we have a seemingly ‘spontaneous’ convergence of characteristics – the emergence of a clear-cut order - on a grand scale. Devoid of conscious human intention, one can only take the evolutionary view that the emergence and evolution of architectural styles is a product of the interaction of many thousands of agents taking place over long periods of time.


The development of evolutionary theory from its origins in biology to its current state as means of studying the behaviour of all adaptive systems makes it one of our most powerful tools in the search for the laws which underlie the processes of change in the material and social worlds. Yet the key concepts of biological evolution and of evolutionary theory, in particular those of reproduction, heredity, variety, the mechanism of natural selection, the role of the environment and so on are all potentially translatable into equivalent processes in the terminology of social or cultural systems including architecture.





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