The Evolution of Modern Architecture
On the Origin of Styles

Chapter Two: Processes and Concepts

1.0	An Outline of the Theory of Evolution

Evolution in architecture must be dealt with in the same way as other large scale natural or cultural phenomena such as ecological, biological, social or linguistic systems which display similar dynamic and adaptive characteristics. Whether as species, styles, social institutions or languages, such systems reproduce themselves, are adaptive to their environments and are able to transmit those adaptations to future generations thus transforming themselves over time. Within their general characteristics they are also able to generate a variety of responses to local environments and, at apparently random times in the history of the system certain of these varieties become extinct to be replaced by others. However before these and other evolutionary concepts are applied in detail to architecture, it is necessary to more fully examine them in their original context within the Theory of Evolution itself. It may then be possible to match equivalent processes and events in different biological or cultural systems.

The key characteristic of any evolutionary system is that it should display reproduction, heredity and variety. Equally, the mechanism by which such systems form and transform themselves is not random or individually chosen but involves a general selection or filtering of group characteristics in terms of their adaptive performance in a particular environment. Here we must define the environment as a total ecological system including all the plants and animals which inhabit a particular geographical area. It would also include the climatic and geological characteristics of the region. Needless to say, given its complexity an ecological system is in a continuous state of change as its many variables interact with one another. In the standard Darwinian model used in the biological sciences, this filtering out of organisms by the environment is called ‘natural selection’ and simply means that organisms which develop successful adaptations to their environment survive to produce more offspring than unsuccessful variations. Offspring which through the mechanism of heredity, have the same adaptive traits are thus equally capable of ensuring their potential to survive. Assuming a particular environment stays the same, the organisms having these successful traits will grow in numbers. Continuous variations in the environment including possible intrusions by other species will test their adaptive flexibility by requiring further adaptation and thus new forms of behaviour or migration to new habitats. Failure to cope with new environments or random variations within the same environment reduces the reproductive rate of a species and thus its capacity for survival. It is worth noting here that it is the environment which does the selection, not the species, or, more precisely the organisms which together make up the species. One can imagine that the biological (genetically induced) form of an organism is a question put to the environment. The answer comes in the form of the reproductive success (or otherwise) of the organism. What organisms do is to adapt to given conditions. Thus the slogan ‘survival of the fittest’ as it is popularly understood completely misrepresents the integrated nature of ecological systems by assuming that the capacity for survival is inherent to the organism itself – its physiognomy or its behaviour. The assumption being that a particular form is good for all times and all places. The reality is that the survival or otherwise of organisms is entirely dependent on the conditions prevailing in a particular environment. It’s really a matter of chance. In other circumstances the same physiognomic characteristics might lead to the extinction of a species. Adaptations are always adaptations to particular places and particular times. 

Continuous adaptation to meet new environmental circumstances produces continuous phenotypic change (in body form and behavioural characteristics) in organisms 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. It is also possible that through random genetic change in the population part of the original species may develop different adaptive characteristics and branch off from the main population. If that new adaptive behaviour is successful in dealing with the environment and if they can reproduce in sufficient numbers they will form a new species with its own unique characteristics and evolutionary history. Both the ancestral and new species will continue to transform themselves over time by adaptation to their environment. This gradual change of characteristics in response to varying environmental conditions is how Darwin explained the ‘origin of species’ and the key aspect of it is the process of adaptation of form or behaviour. (Darwin himself described the process as ‘descent with modification’). For Darwin and for evolutionary theory generally new species are transformations or modifications of some original or ancestral species. There is no spontaneous emergence of new species nor do they miraculously appear wholly-formed in the biosphere. From a biological point of view the fundamental difference between any new species and its antecedent form is not necessarily observable physical differences (in some cases there may be few), it is the gradual emergence of a reproductive barrier between them. This indeed provides us with one of the definitions of a species, namely that group of organisms which are able to breed successfully together. More succinctly, a species may be defined as a reproductive community of organisms. Speciation may also happen for instance through the migration of part of an original  species to another habitat where over a long period of time their adaptation to different conditions from the main body of the species leads them to become in effect another species quite unable to interbreed with the members of the original population. The formation of new species can therefore happen either through the continual transformation of a single species, the genetically-induced and essentially random branching of part of an ancestral species or through the geographic splitting of a species by migration. Whatever the means by which a species is formed, successful reproduction – the production of offspring - follows from the economic success (acquisition of resources for survival) of the organisms in adapting to their environment. To put it simply and obviously, survival comes before reproduction. 

However, successful adaptations whether in body form or indeed the capacity to adapt itself must be transmitted to future generations of the species for it to survive. Heredity is the mechanism of transmission and its operating system is the genetic code written out in the DNA molecule which is passed with variations from generation to generation of members of the same species. 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 or rather about the adaptations which allowed their antecedents to survive. These sets of instructions are copied into the cells of new organisms ensuring a variety of characteristics by combining the genotype of both parents. With this combination of genes, new organisms are thus both similar to their parents and different, maintaining their adaptive advantages while offering the possibility of new kinds of adaptive response to new or the same environmental conditions. Again assuming more or less similar environmental conditions over time, the selection process on a species is cumulative. That is, the same environment will select for the same or better adaptations and winnow out those which do not work thereby over time reinforcing the presence of certain genetic combinations at the expense of others. In the latter case, the organisms which express those disadvantageous genetic combinations in their physical form or behaviour will not survive to reproduce. It is in this sense that one can substitute the more precise term ‘cumulative selection’ for the earlier and somewhat more vague term ‘natural selection’. The potentially lethal consequences of the narrowing of the gene pool in this way over long periods of time is offset by the genetic variety endlessly produced by the combination of different parental genotypes.

Out of all the possible genetic combinations in a population – the gene pool - and their physical and behavioural expression in the phenotype, only a certain number will be passed on in the form of the next generation of organisms. However, except in extreme cases such as desert, high mountains, the polar regions or in the depth of the oceans, the natural environment  - the biosphere - allows for a variety of different responses to its conditions and thus allows for the possibility of a large number of different species to co-exist in the same environment. The selective pressures of the environment on the form of organisms are not therefore totally determined but rather provide a set of constraints within which a large range of organic forms are still possible. This important point can be effectively summarised with the general statement that constraints do not tell an organism what to do (or what to be), only what it cannot do (or what it cannot be). In other words while they place limits on possible developments they do not determine what developments will take place within those limits. There is in other words a ‘free space’ within which different things can happen and different organisms can emerge.
2.0	 Evolution and Architecture: Related Concepts

2.1	Adaptation: Articulation

Adaptation is essentially about the change of characteristics brought about when a group of organisms is subject to selective pressure from its environment. Through the process of natural selection, certain characteristics (physiological or behavioural) are favored at the expense of others in the sense that some organisms are able to acquire the resources necessary for survival and reproduction more so than others. They are more adapted to their environment than others. The advantageous traits (written out in DNA) of one generation are passed to the next through reproduction. The physical and behavioural characteristics of this new generation of organisms are defined by these advantages and can be assumed to be more or less well adapted to their environment assuming of course that the environment has not changed in the meantime. 

‘Adaptation’ when treated as a noun is the physiological or behavioural difference between the forms of one generation and the next within the same species. Continual selection and therefore adaptation over long periods of time may result in the formation of new species which diverge in character from an ancestral species. Used as a verb, ‘adaptation’ refers to the process whereby species characteristics are changed over time in response to their environment. This is a functional definition of evolution itself.

In architecture, the equivalent process would be that of the articulation of the typical elements of a style in response to changing institutional (environmental) demands. This can be clearly seen from architectural history where the original character of a style is subject to continual modification over time. This is usually seen as an increasing complexity of form (eg. from Renaissance, through Mannerist to Baroque) but can be more precisely identified as a process of articulation whereby there is an increasing emphasis or reinforcement of certain characteristics of the style rather than others. As with biological adaptation this takes place from generation to generation with articulations from one generation of buildings within the style being passed on to the next and it is with these modified forms that architects must again attempt to represent social institutions. Articulation like adaptation results from the attempt by architects to represent social institutions by manipulating the range of stylistic elements at their disposal. In each and every case this requires a modification of the typical elements to make them fit the particular circumstances of each design its particular environmental demands. The collective effect of this is a gradual stylistic shift in the elements and character of the style. 
3.0	Evolution as Selection and Combination of Experience.

While human beings are biological organisms, social interaction between them produces patterns of behaviour that can be collectively defined as culture. These patterns or similarities arise through the communication and exchange of experience between the members of particular groups. This produces the mutual coordination of their behaviour through some form of group selection into a set of routines typical to each of the systems which collectively make up a society. Within architecture, the medium of exchange of experience is that of built form. It is this, or rather reports about this, which is communicated between the members of the architectural group and which, theoretically at least can be essentialized into a few elements and relationships typical to the whole range of architectural production. This typical set of forms and behaviours defines the repertoire of possible elements available to the members of the group and acts as the norm, the standard or the canonical form of behaviour through which the members of the cultural system address or represent the general conditions of their environment. Individual members of the group select and combine these typical elements in order to model particular aspects of that environment. Exactly the same processes of communication and exchange can be found in biological systems where exchange through sexual reproduction produces a range of genetic characteristics which define the behavioural and physiological possibilities available to organisms within a species. Clearly this range or repertoire places a limit on how well a system can adapt to changes taking place in its ecology. Since a system’s repertoire of behaviours is based on previous interactions with its environment, it may be that a system faced with radical or sudden environmental change simply does not have the capacity to deal with it. No combination of its available routines can be composed to map those changes. In these circumstances the system cannot coordinate its behaviour with that of its environment. In situations like this, the end result may be the extinction of the system or some catastrophic re-normalization which fragments its organization into a number of residual groups focussed on distinct ecological niches. Even this can be seen as a form of adaptation. The origin or extinction of biological species or the emergence or demise of architectural styles reflects the historical results of this cumulative process of adaptation.

When viewed as adaptive systems therefore there are major similarities of process between biological and cultural systems. The only difference is that of the specific medium of exchange used within each system. In biological systems that substrate 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. 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, exchanged within the system and written out or materialized in the form of a new generation of individual organisms, types of social behaviour or the shape of artifacts. The evolution of adaptive systems whether biological or cultural is thus an active product of collective behaviour – the continuous recombination of available information and thus the construction of ever-new models of the environment.
4.0	Evolution as a Constraint on Variety

The term ‘dynamic’ when used to describe adaptive systems suggests that systemic change is not imposed from ‘outside’, but is a function of the activity of its many agents. The activity in question being that of adequately fitting their behaviour to the very particular circumstances and local environments in which they find themselves. The cumulative effect of these innumerable local decisions of selection and combination of form transmitted to the next generation is a gradual change in the character or behaviour of the system as a whole; in other words, its evolution. One must distinguish here between the particular and the general conditions of an environment. No environment is totally uniform in its characteristics but varies over time and location within a definite range of possible states. It is therefore more useful to regard the environment as a constellation of niches (micro-environments) each of which demands more or less different responses from individual agents to its very particular conditions. It is at this micro level and at this scale with its endless diversity of real and concrete problems that individual agents operate and within which they deal with the economics of survival; the daily extraction of the necessary energy and resources that allow them to survive and reproduce. Their success or failure in this activity is, in the end a function of the genetic possibilities which they have inherited from the ecological history of the species and the incarnation of that history into the form of the organisms themselves. In other words they are designed by history to operate within a limited range of behavioural possibilities and within a limited environmental range. Genetic differences between individual organisms (a product of random combination of genes drawn from the gene pool of the species) varies the success rate of some individuals over others in particular environments.  It is not that some survive and some don’t. All of them die eventually. It is the fact that success in the economics of survival (“Eldridge’) allows some organisms to reproduce at a greater rate than others. Successful genetic variations are transmitted to a new generation of organisms as adaptations of an antecedent set and these adaptations gradually alter the characteristics of the species as a whole. In a sense of course the species itself can be considered to be a series of adaptations. (“the species as a snapshot’). The whole superstructure of species and its genetic characteristics is built on the exchange of genetic information drawn from the experience of a multitude of individual organisms. In this sense the concept species is entirely a collective idea dependent on (genetic/reproductive) communication between individual organisms.

We can detect very much the same system-environment relation in cultural systems. Here too the whole structure of architecture, its stylistic coherence, its transformation and the collective constraints on form are the cumulative product of a large number of individual experiments written out in the form of buildings. So too the socioeconomic environment within which it operates varies from place to place and time to time analogous in its own way to the niche organization of natural systems as described above. In other words there is no ‘real’, general or uniform environment. Thus, it is not possible to build exactly the same building twice given the endless variations of location, economics and technology which architects deal with in their individual projects. As usual, context is everything and defines the (micro) environment in which particular buildings take shape. 

The evolution of a collectively-defined architectural repertoire – the style - involves many individual architects solving their own very particular design problems. They do this by incorporating and adapting the experience of others; in other words by exchanging information about those experiences. Each of these architectural projects is an attempt to map the form of a particular social institution into the language of built form available to architecture at the time. Here architecture as an institution and as a cultural system seeks to represent or model the nature of other cultural systems. This modelling of other institutions (social, commercial or governmental) as they manifest themselves in particular locations is exactly what design means in architecture. This corresponds to the biological process of adapting behaviour to local environmental conditions. In the case of architecture of course the process involves combining architectural elements including ‘space’ to suit an environment defined by some social institution or other. In this sense of course the process is just as material and concrete as that carried out by biological organisms in their struggle to find adequate energy resources. In both cases, whether building or organism, the result is a material form whose shape is in part a more or less successful ‘diagram of forces’ of the organization of its environment. However, the success or failure of that process in individual architectural projects is determined not only by how well the design solution represents the organization of the institution in a strictly functional sense. For a cultural system it also involves the semiotic dimension of how successfully the form of the institution is expressed in this place and this time. In other words in a particular context. This is not in any sense an abstract requirement. The physical form of a building is shaped by a multitude of contextual factors. However, one of the major constraints in the design of buildings is the limitation provided by the state of the architectural language at the time. That is, by the available stylistic repertoire – the typical set of forms derived from the past which is available to the architect to represent an institution of any sort. This historically-defined repertoire defines the limits of what it is possible to say in exactly the same sense that any language allows or limits the expression of ideas. The architect must choose from this set of forms in order to achieve a coherent expression which means something in a particular time and place. 

For biological systems of course this same kind of limitation is provided by the genotype which defines the range of possible forms and behaviours (the phenotype) of any organism. In both cases ‘mutations’ are possible in the sense that the architect might deliberately choose forms which are outside the current typical set or a error in the genetic copying process might produce an organism with a form or mode of behaviour untypical of its species and the particular environment for which that species has been ‘designed’. In most cases mutations do not survive or reproduce. They are not designed to function in the environments which they inhabit. The typical set of an architecture or the genetic set of a biological species while in one case limiting design possibilities also provides a ready-made and tested formula for successful design within the current environment.

5.0	Reproductive Success in Architectural Terms

To get an equivalent process in architecture to the concept of reproductive success in biological systems we have to recognize that once built, all buildings become the imitative source for future buildings. Communication and exchange between architects produces in effect a mutual analysis and ‘deconstruction’ of each others work into individual elements or combinations. Thus architects as a group filter the ‘raw data’ of numerous individual experiments into a virtual coherent generic set which can be identified by the repetition of certain elements and combinations throughout architectural production. Collectively, this is the typical set of architecture at the time from which individual architects select forms appropriate to each project. The selected elements are then simultaneously modified and combined into a single form, a building which more or less successfully represents the unique conditions of a local environment. 

In this collective process successful combinations of form become the source for more imitations. In the biological sense, they ‘reproduce’ more successfully than others with these combinations of form being passed through to the next generation of architects as part of the typical set. It is not whole buildings which form the basis of the typical set, but particular aspects, elements or forms drawn from those buildings which can be combined in turn with other successful combinations of form drawn from different sources. The typical set is nothing if not a consensus drawn from the experience of many individual projects. Constant exchange between architects produces a convergence of form between many buildings; a convergence built on the interchange of successful experiments which become recognizably members of the same representational group; the same style.

The analogy with biology is quite clear. Success in adapting to the exigencies of the environment and doing so with minimum energy costs, (the economics of survival), allows an organism to reproduce itself (or a particular genetic combination) in the form of future generations. The issue of the economics of survival is important here. If an organism needs to struggle to stay alive in a particular environment we can say that it is using up almost all of its energy resources to do so. Energy which would otherwise be used to further establish itself by widening the range of behaviours it can display and thus extend its territory; protecting itself in other words from minor variations in its environment. It thus has options available for future use. Here in the idea of reproductive success and of the economics of survival we also have an interesting link to the concept of aesthetics in architecture which centres around the elegance of the design solution; the use of minimal resources to achieve a maximum return or the other definition: ‘grace under pressure’. One could almost use this as one definition of ‘the aesthetic’ and of the successful design whose form is imitated in future buildings. More will be said of this later. For the moment we can say that the integration of recognizably successful design experiments into the typical set produces a convergence of form in architecture in the sense that they are selected by other architects for incorporation in their own design projects. Quite simply, buildings begin to look more like each other which is of course the definition of the concept ‘style’ .Here now we have a familiar repertoire of forms available for recombination in new projects. However, theoretically, over long periods of time and in a super stable environment this would lead to a lethal narrowing of the range of forms available to architecture and a reduction of its semiotic freedom – its ability to freely express what it needs to express. The consequences would of course be that architecture would be less and less able to accurately represent new environmental conditions since it is locked into an historically-confirmed and severely limited set of typical forms which are overly similar. However, this is an unusual event due to the large number of projects being built, the unique characteristics of the many institutions being represented, coupled with the variety of spatial, economic and technological constraints which operate in each case. These lead to the production of an endless variety of architectural solutions all, admittedly variations on a central stylistic theme. Normally in both architecture and biological systems there is a coexistence of and interplay between diversity and similarity of solutions.

Again, theoretically, the opposite problem could arise whereby over time architecture would diverge in its characteristics to the point of being quite random where every building would be very different from every other. In this case the typical set would dissolve into an infinite number of individual experiments. However the process of selection which arises in the communication and exchange of experience between the agents of the system constrains this divergence and places a limit on the degree of difference between individual group members. While individual buildings may well be different from one another, they maintain a similarity of form and thus a coherent meaning because they use the same set of typical elements. Group selection ensures that a definite order or pattern is maintained in the form of a typical set of characteristics which may be modified to suit particular circumstances but which still retain their collective identity. This is the product of mutual selection applied to previous individual experiments in modelling or representing local environments. It is this generic set which is subject to adaptation in evolutionary terms in much the same way that the genetic characteristics of organisms are subject to adaptation. By analogy, the typical set of forms of a cultural system can be equated with the genetic complement (the genome) of a species which determines the physical form and range of behaviours available to its individual members. Like the environments which they represent both the typical set of the cultural system and the genetic ‘set’ of the biological species are subject to change over time. They are virtual entities which at one level merely reflect similarities of form or behaviour between the agents of a system. At another, they are organizational events or meta-systems which arise in the interaction between the agents of a system and constrain their behaviour and define the collective dimension of the system. In other words, the continuous and cumulative process of communication and exchange can result in the emergence of new styles, new sets of behaviours. The typical set (whether genetic or cultural) defines the rules which govern the form or behaviour of the individual members of the group. In both cases they also act as the (selective) memory of the system by re-calling in their own virtual forms, the history of the system’s relationship with its environment; its memory.   

The key factor in the evolution of both these systems is that their respective processes are continuous and cumulative. Adaptation of the typical set occurs after forms have been tested in the environment combined and recombined in numerous individual projects or in the shape of individual organisms.  The results are processed collectively by exchange of information between the agents of the system and the result is the emergence of a revised set of typical routines offering a new range of possible behaviours. Adaptation simply refers to the results of the process of modification of form, namely a new configuration of form. That is, the current state of things. While individual projects represent particular environments, the typical or generic set of a system can be said to represent the state of the environment ‘in general’. In a limited sense one can imagine that this is the map the system as a whole uses to guide its behaviour in a complex environment. While one can theorize about this total system and spend many happy hours discussing it, the reality of the system exists at the level of individual actions and the selection-combination processes of individual agents. 

Yet, there is an inherent limit to the capacity of any system to model or represent the complexities of its environment. In every single case, whether biological, architectural or mathematical, the modelling of a natural system by any other system will inevitably be a compromise. The map cannot match the complexity of the territory. What this means of course is that there is always the danger of failure in the attempt to coordinate behaviour with external conditions especially since those conditions are not fixed but variable. Here is the complexity of the design problem that the design solution must involve multiple adaptations of the prototype (the generic form) to make it fit a very particular set of environmental circumstances not all of which can be individually articulated and resolved. In the integration of these factors into the evolving design, there is an inevitable and even necessary simplification of the nature of the target environment; a tendency to focus on its major regularities rather than its inherent diversity. This is not only a matter of the economics of design time but stems from the impossibility of ever fully transcribing the analogue (seamless) reality of an environment into its precise representational and therefore digital equivalent. To be used at all, the language of representation must involve the introduction of gaps and boundaries which are arbitrary relative to the target environment since they stem from the logic of language itself; its need to utilize precise combinatorial units. The result is that to some extent or other the model or design of whatever kind will be an approximation. This applies as much to the modelling process in natural systems as it does to cultural systems. Quite simply, not all problems can be adequately stated never mind solved and there is always room for error whether genetic or behavioural.
6.0	Evolution as History

Adaptation is a product of an exchange of information within the system based on ‘reports’ by numerous individual agents about conditions external to the system. The result is the emergence of a new set of typical forms and therefore a new range of possible combinations of behaviour. This continuous activity takes place even when the ‘general environment’ is stable. That is when it remains within the same range of variables.  Since individuals do not deal with this abstract concept ‘environment’ but with the reality of different niches or micro-environments, variety of behaviour will continue to be produced. 

Yet even discounting the inherent variability of the environment, one can suggest that the continuous combination and re-combination of differences within a given geographical area will inevitably produce differences. The interaction between individual agents does not stop no matter what the environmental conditions. In this perhaps we may have a clue to the origin of the pattern or order exemplified in the typical set of a cultural system. One can imagine for a moment therefore, that in a stable environment the history of an adaptive system such as architecture would evolve through a series of organizational states. This would happen purely because of the exchange processes taking place within the system; an exchange of information between architects. The result of this continuous activity might range from an initially ‘chaotic’ state where there are a large number of different behaviours, through to the formation of small interacting groups and finally to the emergence of totally coordinated behaviour where the system would in effect function as a single entity. Initial differences of behaviour would be subject to a form of selection where the constant exchange of characteristics within the group would result in the convergence of behaviour by the elimination of extreme variations. This would occur as a result of the economics of the selection-combination process where almost similar characteristics derived from different particular circumstances would be merged into a single generic form. In the multiple selection and combination of forms derived from the past there would be a tendency to essentialize the differences between different forms. It is suggested here that the multiple selection and combination of forms from previous works automatically eliminates extreme variations resulting in the emergence and maintenance of a consensus-driven repertoire.

This economy of effort would automatically establish a standard or canonical form of behaviour. More specifically in the language of architecture, it would result in the formation of a characteristic style – a template - which could be applied to (combined for) many different situations. In biological terms it would mean the convergence of genetic characteristics around a particular set of gene frequencies and thus the formation of the characteristics of a particular species. The importance of this group selection process and the production of a standard mode of behaviour is that it automatically places limits on how organisms or human agents can respond to their environment by defining the possible range of behaviours that can be called upon to model, represent or adapt to the environment. In other words it defines the degree of semiotic freedom available to the individual agent and the combinatorial choices that can be made in any given situation. 

As suggested above, even when the behaviour of the individuals within the system achieves a high degree of coordination within a stable environment, the system will continue to change. The communication and exchange processes do not stop at some notionally ideal or integrated state, they are continuous. The purely theoretical question is of course what else is left to do once the system is integrated both internally in the sense of coordinated behaviour and externally in the sense of being more or less adapted to its environment? The answer is: to do what it normally does, namely exchange and combine elements from the typical set and test them in the environment. The result is the production of difference, but difference of a different kind. In this case the fragmentation of the group with the production of ever finer or small scale adaptations to local environments. One must remember that the environment is not a fixed and uniform field but a collection of micro-environments of finer and finer grain. In a stable environment continuous adaptation in fact produces a splitting of formerly coherent groups into sub-groups each more finely tuned to a particular and smaller scale of the environment. In the case of a species which in the first place is not a completely unified group of organisms, the result is a gradual specialization of small groups around ever more unique habitats. The cumulative effect of this over time is the gradual genetic differentiation of these sub-groups as they become subject to different selective criteria from their respective environments. The genetic effect and ultimately the physiological effect of this specialization is the establishment of a reproductive barrier – they cannot exchange information between them - and thus their emergence as different species. 

For architecture, the fragmentation of a formerly coherent style arises through the application of exactly the same selection-combination processes as before, but now taking place in a different context. That context is the presence of the unified style itself and its current set of typical elements. These were a product of the merging of ‘almost similar’ experiences into their most essential or generic features. It is the similarity which is now articulated and subject to ever finer sets of characteristics and ever finer articulations. The result here is the splitting of the elements into contextual or circumstantial features and ‘deeper’ or ‘more essential’ features.

Needless to say, with variable or unstable environments the same adaptive and combinatorial processes might also involve the fragmentation of formerly coherent groups, (say species or styles) into specialized behavioural niches or multiple styles. The same rules applied in different contexts produce different end results. In both cases evolutionary change is a matter of the re-organization of the system as a whole with the grouping and re-grouping of the behavioural options within the system. 

A systematic history of a stylistic period would endeavour to track these evolutionary trends from chaos to order or vice versa as a function of adaptive change derived from continuous communication between architects in a defined environment. One must remember here that the environment of each individual architect is the work of all other architects. In other words styles emerge or evolve because architects are adapting to each other’s work by the mutual selection, exchange and re-combination of architectural elements that are drawn from the experiences of all members of the group.
7.0	Environment and System

We can identify the source of evolutionary change in any dynamic system to be its attempt match its behaviour to conditions which prevail in an environment of which it is an integral part. However the behaviour of a system is not completely determined by outside factors. It is also a product of the repertoire of behaviours it has acquired and ‘remembered’ from previous interactions with its environment, from the inherent variety of behaviours to be found amongst its individual members and the continuous interchange and combination of their characteristics. In other words a system can only respond to events by manipulating and combining the range of behaviours it has available at the time. In this sense we can say that while the system is autonomous it is, however locked into an inescapable relationship with the many other systems which make up its environment. The behaviour of the system is for this reason, non-linear since one cannot predict it from an analysis of the current state of its environment even if that were possible. There are too many internal variables at work within the system (its memory and the numerous interconnections between its agents) which determine how it’s going to behave at any given time. However, the dependent relationship between a system and its inherently complex environment requires that the system model its behaviour on the collective state of those other systems by a trial-and-error combination of its behavioural repertoire. In doing so it must continually adjust or adapt its behaviour accordingly. Thus the core of evolutionary theory lies in this in-built modelling relation between systems of whatever scale and their environments. 

If we define  ‘environment’ 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 we can see that change (of characteristics or behaviour) will be a constant feature of all systems. The environment is not in other words an abstract entity with fixed characteristics to which each system responds. It is the name for a group of systems interacting with one another In other words, the concept should not be reified by regarding it as a separate system which is somehow different to or which in some way ‘controls’ all the others. It is not. The term ‘environment’ is simply a collective term – a classification - given to this set of interacting systems. In a more direct sense we can imagine the environment not as an entity but an event. That event is the mutual adaptation brought about by communication between systems. It was pointed out previously that conditions vary within the boundaries of an environment. Described in ecological terms, it is made up of a group of niches within which conditions are more or less stable. In this definition, therefore the concept of ‘environment’ is entirely relative. It is defined by an observer. Once a particular system is identified, this automatically defines its environment, namely, all other systems. 

When looked at as a whole this constellation of systems itself can be seen as a system that, in turn has an environment and so on. One embedded within the other. In a scaled-down version of this global relationship, each system in turn provides an environment for its component parts each of which adjusts to the changing characteristics of all the others. There is, in other words a hierarchy of scales based on the same organizational template of a group of components mutually adapting to one another. It is the relationship of communication and exchange between these components and the adaptive changes brought about by this relationship which is significant and which allows us to define the concept ‘system’ in evolutionary terms. 

For instance, the concept ‘species’ does not indicate a group of organisms which have a uniform set of characteristics but rather a group of individuals whose characteristics vary but within definite limits. Again, like the definition of environment given above, these concepts are classifications not entities. Variety in the form of the numerous individuals who make up a system remains an inherent aspect of evolutionary theory. So too do the limits to that variety which constrain the form and behaviour of those individuals. Limits which are derived from the self-organization of systems –the cultural or biological interaction – between those individuals. Whether a system is made up of human agents, biological organisms, corporations or other systems is not the issue here. What defines the concept ‘system’ is the fact that its constituents can exchange characteristics between each other. In a sense they speak the same ‘language’. For instance, the biological definition of a species is that of a ‘reproductive community’. That is, the organisms within that species can exchange genetic information (and ultimately physical characteristics) through sexual reproduction. They cannot however, exchange characteristics with organisms from another species. The boundary of a species and thus its definition is a reproductive or, in more general terms, a communicational boundary. So too with other kinds of systems. In architecture for instance, the currency or language of exchange is built form. In economics it is money. In music it is patterns of sound. These different internal languages prevent the exchange of characteristics between these different fields and thus define their system boundaries. 

So at one level this definition allows us to differentiate different kinds of system from each other, for instance economic, biological, cultural or whatever while at the same time indicating their fundamental similarity of internal process: the process of communication and exchange. So, like the term ‘environment’ defined above, the term, ‘system’ itself should also be seen as a collective name for the communication and exchange processes which link a large number of individual agents into an organized group. It does not have a separate existence from those agents. Indeed, in a sense it does not have an existence at all. It can be seen as a statistical regularity – a similarity - which informs the behaviour of a number of individual agents. It is they who grapple with reality in the attempt to fit their behaviour to particular environmental conditions. ‘System’ therefore is an organizational concept which defines a relation of communication, exchange and mutual adaptation between a number of agents. The evolution of the system – its gradual change over time arises out of this relationship and should therefore should be understood as a result of collective adaptation. 
8.0	Selection and Adaptation

Adaptation – modifying an existing behavioural pattern to suit changing conditions external to itself - is the key process in the evolution of systems. This is why the term, ‘transformation’ is a more suitable for evolutionary explanations that the simpler term, ‘change’. The latter simply denotes an unexplained difference between one state of things and another, while the former suggests that any new state is a modification of an existing state. This view recognizes the continuity of the whole process and equally that any change that takes place is always ‘change within limits’. The limits of course being the initial state of the system and the range of possible behaviours which it can express and combine to suit different conditions. It has been pointed out above that Darwin, in describing what we would now call evolutionary theory, referred to this process simply and modestly as ‘descent with modification’. A modification provoked by the system tracking changes in its environment and adapting its behaviour accordingly. 

Adaptation can also be seen as the mechanism whereby a system seeks to optimize its behaviour. In evolutionary terms this means to coordinate it with the state of its environment. This can also be seen as a process of Design where the ‘goal’ of the system is to achieve a perfect ‘fit’ with its environment thus requiring minimal use of energy to maintain itself in being. In this generalized design process a series of prototypes or design options (of behaviour or form) are developed and tested against the environment in which the system will function. The process of optimization involves the continual and gradual modification of an ‘original’ form, the elimination of certain dysfunctional features at each design stage (each generation in a biological sense) and the reinforcement or modification of others up to a point where theoretically an optimum form has been achieved. Thus the form evolves over time by a gradual selective modification or adaptation of its characteristics. This process obviously corresponds to the mechanism of natural selection in all adaptive systems and can also easily be recognized as a normal procedure in the design professions. In the latter case however, the individual designer acts as the virtual ‘environment’ of the designed artefact in the sense of translating conditions to be found in the real environment in which the artifact will function into design parameters. These act as the selective template which conditions the final design of the object which evolves over time. Selection in this particular case means searching the currently available repertoire of design elements for appropriate or similar solutions to the same problems. It is these typical and familiar elements which are adapted or modified to suit the final goal of the design, namely the accurate representation of a social institution in a particular place at a particular time. They must be shifted and adjusted just to get them to fit together. Here we have a kind of ‘internal adaptation’ One cannot assume therefore that a building or an organism for that matter is simply the product of a one-to-one adaptation to its environment.  Multiplied throughout the work of many designers, the selective process produces a continuous exchange of characteristics between the form of many different designs. It is in this sense that individual design projects can be said to be adapting to one another and through which the architectural system, the style evolves. Each design product is not simply the reiteration of available typical or familiar elements. The design process involves the modification or adaptation of given elements to suit very particular circumstances. Diversity in this sense is built into the system.

Evolution through natural or cultural selection is the ‘search’ for (or the computation of) optimum design characteristics for particular environmental conditions and the adaptive manoeuvres required to achieve them. It has to be said however that at this collective level of the system, this is ‘design without designers’. If anything can be said to be doing the selection it is the blind forces of the environment. While one can say that the system as a whole adapts to an environment, one must also state quite clearly that it only does so through the activities of its individual agents. It is their success or failure to cope with the demands of their individual circumstances which cumulatively brings about change in the system. It is the communication and exchange process (in biological terms: reproduction) between the ‘survivors’ – those with optimum design characteristics - that establishes the new behavioural set, the new style or a new species. Inappropriate or ineffective design solutions simply fall by the wayside never to be repeated. In biological terms they do not reproduce. Thus the state of the system and its prevailing characteristics is the unforeseen result of the cumulative trial-and-error activity of its many agents. 
9.0	Collective Adaptation as Evolution

One of the problems in discussing evolution is the need to refer to the individual and collective levels of activity In standard biological theory groups of organisms (species) adapt in order to survive and in the more literal genetically-based theories of evolution this idea is expanded to suggest that organisms adapt in order to reproduce, driven as it were by their genes. Reproduction in this case being a ‘proof’ of survival. Here again, this time in science, we have an anthropocentric idea projected on to a natural system. Again, individual motivations such as survival and the intention to reproduce are projected on to the activities of the group. We can safely say that only individual organisms care about survival or reproduction if at all. Since groups of organisms or genes for that matter have no conscious intentions, they do not. If they are not ‘motivated’ to do so, why do species adapt or evolve at all? The answer is that they simply do what they have been designed by nature to do, namely integrate themselves into their environment; an environment which provides them with the resources of information and energy through which they operate. In this neutral theory of evolution, systems of whatever scale adapt their behaviour because they cannot do otherwise; they are an integral part of the overall environment. The formation of new species can be seen in the same way, as a biological system’s attempt to fine tune its behaviour by adapting to diverse conditions in its environment. Over time these local differences of behaviour get locked in (reinforced) to the point where an isolated population becomes a distinct and new species. So too, the extinction of a species or an architectural style can be seen as an attempt to re-normalize the relationship between a rigid or deeply-programmed behavioural pattern derived from its past and new and radical changes taking place in its environment. In some cases these are irreconcilable demands. It is changing environmental circumstances and the very occasional beneficial genetic mutation which determines whether the biological group survives. In other words whether their current design or phenotype is appropriate to new conditions. That is whether they can remain an integral part of that constellation of other systems.
10.0 	The Collective Dimension of Culture

If we exclude teleological or anthropocentric interpretations of change in architecture we can see that the emergence or dissolution of major stylistic formations are the product of the most basic, collective and automatic results of the activity of many architects. It is the unforseen result of their individual attempts to produce buildings which in some way or other accord with their social, institutional or technological environment. It must be emphasised that individual architects (no matter how heroic)  cannot even imagine, never mind produce those large scale formations which we call styles which are the product of a collective exchange of information across the whole of architectural production and whose evolving characteristics cannot be predicted.

If we utilize what has been called ‘universal Darwinism’ namely the principles and processes which govern change in any evolving system, biological or otherwise, then perhaps we can provide architecture with a broad conceptual framework where its history and the processes which produce it can be rendered more systematic. In other words, to move from an essentially historical and individualistic approach to the study of architecture where description substitutes for explanation to an evolutionary or systems approach where the dynamics and the processes of change in architecture can be understood as a function of its organization interacting with and adapting to its environment. Evolutionary theory seen from this point of view including the mechanism of ‘natural selection’ would be built on a communicational perspective where the collective products of culture such as architectural styles rise and fall (reproduce or become extinct) through the interchange of information between cultural agents. After all organisms do not evolve, only groups of organisms or species do so by becoming other species. In other words, evolution is by definition a collective process. The ideal situation is of course through an evolutionary or communicational perspective a higher level of explanatory power in the study of architecture.

It is important to note here that nothing is lost in approaching architecture in this way. The individual work in the selection, combination and modification of existing forms remains as important as ever. The issue here is to connect these innumerable efforts to the emergence of the great stylistic systems which have arisen throughout history and to do so in a systematic and objective manner; in other words, to establish an evolutionary history of architecture or, more specifically a history of architecture written out in evolutionary terms. However, before this can be pursued it will be necessary to offer clear definitions of the terms and concepts that will be used in the process.

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