Reviewed by
Frédéric
Amblard
Laboratory of
Engineering for Complex Systems (LISC), Cemagref,
Clermont-Ferrand, France.
As its author introduces it, this book is both an intellectual journey through theories concerning the evolution of human beings and a plea for the application of complexity theory techniques within the social sciences. Even though he remains far from applications to illustrate his arguments, Alan Dean's book is a nice introductory work on the subject. It presents a first depiction of this interdisciplinary domain dealing with anthropology, sociology and cognitive sciences.
The journey begins with an anthropological discussion about the evolution from primates to humans. This chapter succeeds in introducing the reader to some key ideas on human evolution. Dean begins by analysing the old theories of Linnaeus and Gray about the classification of species. These theories aimed at placing humankind in the tree of species by comparing the presence or absence of certain anatomical features. For these authors, what distinguishes humans from non-humans are a number of morphological and behavioural characteristics such as bipedalism, brain enlargement, use of language and use of tools. The tasks of this approach are to establish the nature of the last common ancestor and complete the evolutionary record from that point up to modern humans and then to unfold the quality of the selective pressures from which the depicted adaptations arose.
Dean reports that the emergence of homo sapiens has given rise to several explanations such as climate change, adaptation, concurrence or migrations. However, when the earliest hominids stood up, whether hunting for food or watching for predators, they freed their hands which enabled them to use their fore limbs for tools manipulation. Their brain volume then increased through selective pressures on appropriate cognitive and behavioural traits.
The author then introduces complexity theory to emphasise this point: is evolution a linear or a non-linear process? He argues that it is a non-linear process. The fossil evidence suggests a mosaic pattern of change, rather than a pattern in which the change from one ancestral type to another occurred in a distinct and unambiguous manner. Dean then makes a plea for complexity theory techniques, arguing that the concepts of emergence and interconnectedness of causes and consequences are the key aspects of this theory for our understanding of evolution.
As regards cranial expansion and the emergence of modern humans, Dean recognises the significant roles of culture (language and symbolic reasoning) and the environment. However, at some point, the fundamental circumstances of human evolution expanded to include the emergence of a cultural context to human existence. Interactions between genes and culture are now setting the context for human evolution.
The next milestone in the journey involves the emergence of symbolic reasoning amongst human beings. This gives rise to the use of spoken languages as a mean of communication. As Dean observes, only humankind has grammatically structured languages. Information used by all other social animals propagates largely by the genetic inheritance of behavioural traits. For example, even chimpanzees are limited in their ability to preserve skills and knowledge from one generation to the next. Being able to communicate complex ideas would be purposeless unless it was experienced collectively.
Changes which facilitated the development of language must have taken place prior to the emergence of language itself. Clearly, language and symbolic reasoning could not be the basis of their own emergence.
Dean agrees with Deacon's (1997) theory about the co-evolution of language and the human brain. The ability to reason symbolically and use a vocalised language could have evolved side-by-side. Introducing the role that society played in this matter, Dean agrees that forms of language and the facility to use language co-evolved socially.
However, the ability to reason symbolically must have preceded the emergence of language. Edelman (1989) presents a theory of neuronal selection which Dean discusses. Those neurons that are utilised, or selected for, propagate at the expense of those that are unused. In this way, diversity in the brain morphology derives directly from adaptive processes at the levels of both cellular propagation and early neuronal pathway formation.
Again pointing out that the emergence of our species was an outcome of evolutionary processes, the author pleads for the use of complex systems theory as some of its tools (like strange attractors) share the same structure as systems of this kind. Humankind is then travelling through an n-dimensional natural world along the path of a strange attractor.
In regard to the origins of symbolic reasoning the author states that big changes involving substantial morphological shifts can only occur adaptively over long periods of time. Some people like Gould and Eldredge (1993) have argued for pre-adaptations without stating how these may have arisen, whereas Dennett (1995) prefers a theory of nested adaptations. Dean seems to share Gell-Mann's (1984) point of view, arguing that human evolution is a complex adaptive system.
The third chapter deals with the link between cognition and adaptation. Dean states that cognitive abilities arose through natural selection before cultural selection or social learning. His theory goes as follows. As the use of tools requires not only high levels of manual dexterity but also the ability to think abstractly, the human being acquires the ability to make an abstraction of the tool, linking an object to its function. From this arose symbolic reasoning about these tools. Symbolic reasoning can then extend to other fields, mainly the social field, by experiencing the social environment. The language emerging from symbolic reasoning provides the social basis of the evolution of human cognition.
Naturally, the fourth chapter examines how the early hominids encountered the cultural world. Dean starts by describing Plotkin's (1994) theory about instincts as being species-specific behaviours that are structured inside the brain through natural selection and elicited by environmental events, just like predator avoidance. Following from this, the context of a linguistic and collective social life has evolved into Darwinian cognitive algorithms. What Dean calls adaptive rationality is thus a property of social interaction: adaptive rationality refers to certain mental abilities rather than intended computations.
The ability to analyse and represent the external world symbolically enabled humans to think creatively about it. Sharing Edelman's (1992) point of view, Dean explains that the ability of higher-order consciousness to interact with the external world symbolically enables the creation of abstract symbols about the present which can be remembered and used to reflect on future events. Elegantly, he thus justifies the link between humankind the problem solver and humankind the speechmaker. From then on, the emergence of categories in cognition can perhaps best be seen as an outcome of social interaction. For this reason, Dean argues that it is most likely that the further evolution of language was driven more by social and cultural events than natural selection acting through the physical environment. Human reasoning has then evolved discontinuously in response to adaptive forces of both a natural and social form. Human consciousness and languages have co-evolved. Dean then defines the next stage of human evolution as a system of feedback and feed-forward between nature, culture and cognition.
The author examines the shift of natural selection into cultural selection when most of human social and personal life is still determined by nature through our biological structure and environmental constraints. Nature and culture are indivisible parts of human life. Mind, society and nature are then inextricably linked. Taking the example of the incest taboo, Dean exposes some cultural traits that impart a survival advantage. This advantage could be that the more widespread the out breeding, the lower the frequency of expression for lethal traits. But as Dean points out, incest may confer advantage when mating with a stranger involves risks. For instance, little is known about either their genetic wellbeing or their abilities and commitment to parenting. Another interesting idea is that for some populations (suffering from a lack of opportunities to outbreed due to social or geographical isolation) inbreeding is commonly practised. Then, selective forces would act over time to limit consanguineous mating between close kin. However, wherever there are few opportunities to mate due to social or geographical isolation, consanguineous mating will be advantageous because without it there won't be any possibility to have offspring at all.
The psychological and sociological parts of the explanation for the incest taboo come from Freud (1960) and Malinowski (1960). Sexual attraction exists between members of the same family in an impulsive way and these impulses can only be moderated through social prohibition. There is then an interrelationship between biological influences and social practices. One proposal is that if there were an aversion towards incest there would be no need for laws and norms to prohibit such acts. Then, as each individual's disposition towards sexual activity will be unique, arising both genetically and through developmental processes or behaviour, it will be structured through social norms and institutions and will thus appear largely uniform.
Returning the debate to the redefinition of methods and frameworks used in the social sciences, Dean begins his sixth chapter by justifying his claim that the social world is non-linear. Certain components of cognition and cultural life can be understood as being the expression of an underlying causative agency that has occurred through selective processes, within a complex, multidimensional and interconnected material world. As an example, a spider's web will vary to some extent from any other construction of the same type as a product of the prevailing material conditions. Certain material conditions may lead to cultural practices that engender particular family structures.
Dean then attacks the basis of the modern social sciences arguing that these are based on a desire to realise the kind of systematic knowledge associated with the natural sciences. Dean cites Mills (1959) when exposing the inability of humankind to comprehend the totality of its rational, social, industrial and economic constructions.
Dean then refers to Latour's (1993) thesis which states that a key claim of modernity (that nature and society are separate) is based upon false assumptions. Everywhere scientific projects are infused with cultural moments. This thesis is often summarised by its title "we have never been modern". What Latour reproaches modern social science for is three basic assumptions. Firstly, that although humans construct nature, nature is as if humans did not construct it. Secondly, and conversely, that even though humans do not construct society, society is as if it is constructed. Finally, that nature and society must remain absolutely distinct. These assumptions are false and Latour wants to reclaim the middle ground between nature and culture and to reassert the importance of the indivisibility between nature and culture in the shaping of human events.
Starting from the duality of the subject and object in human agency (the subject is both knowing and known), Dean then suggests that complexity theory can provide a starting point for such a project of reconciling nature and culture. He claims that change within both natural and cultural networks can be understood as arising from causative mechanisms that underpin the multidimensional cognitive, social and cultural world. Complexity theory and human evolutionary theory, if combined, allow for another approach within which nature and culture are inseparably interconnected.
In conclusion, Dean makes the observation that complexity theory reveals that outcomes observed at the macro level arise as a consequence of interactions taking place at deep levels within a system. This, for him, constitutes a strong argument for the use of complexity theory tools and techniques to understand human evolution.
To sum up, this book is quite a pleasant journey through the existing theories on human evolution. However, the part about the use of complex systems techniques is less convincing. Even though I personally believe in such a meeting of methods, the proposed arguments concerning the similarity between systems and tools are not sufficient. There are actually more suggestive examples illustrating Dean's purpose to be found in the work of Kauffman (1995). One last disappointing aspect of this intellectual journey is that it feels like it is being made in a small plane without a compass. It is not particularly pleasant at times and does not really take the most direct route. The itinerary for the journey is spectacular but unfortunately, the lack of illustrations and examples makes you feel you are travelling behind closed curtains. It is as if you are allowed to make the trip but not to see the landscape clearly. This is even more disappointing as the in flight commentary allows you to imagine how marvellous the landscape must be!
ReferencesDEACON T. 1997. The Symbolic Species: The Co-Evolution of Language and the Human Brain. Allen Lane, London.
DENNETT D. 1995. Darwin's Dangerous Idea: Evolution and the Meaning of Life. Penguin Books, London.
EDELMAN G. M. 1989. The Remembered Present: A Biological Theory of Consciousness. Basic Books, New York, NY.
EDELMAN G. M. 1992. Bright Air, Brilliant Fire: On the Matter of the Mind. Penguin Books, London.
FREUD S. 1960. Totem and Taboo. Routledge and Kegan Paul, London.
GELL-MANN M. 1984. The Quark and the Jaguar. W. H. Freeman and Company, New York, NY.
GOULD S. J. and N. Eldredge 1993. Punctuated equilibrium comes of age. Nature, 366:223-227.
KAUFFMAN S. 1995. At Home in the Universe: The Search for Laws of Complexity. Oxford University Press, New York, NY.
LATOUR B. 1993. We Have Never Been Modern. Harvester Wheatsheaf, Hemel Hempstead.
MALINOWSKI B. 1960. Sex and Repression in Savage Society. Routledge and Kegan Paul, London.
MILLS C. W. 1959. The Sociological Imagination. Oxford University Press, New York, NY.
PLOTKIN H. 1994. The Nature of Knowledge. Penguin Books, London.
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