Smith and Szathmary, The Major Transitions in Evolution
CHAPTER 1
1.4 The major transitions
A tentative list of the major stages in the evolution of complexity, and the transitions between them, is given in Table 1.2. We have confined our attention to the way in which information is transmitted between generations, so have not included major phenotypic changes, such as the conquest of land by plants and animals, or the origins of vision, or of flight or of homiothermy, which did not involve such a change in the method of information transmission.
One feature is common to many of the transitions: entities that were capable of independent replication before the transition can replicate only as part of a larger whole after it. Some examples will make this clearer:
The origin of chromosomes. Initially, there were independently replicating nucleic acid molecules: after the transition, a set of linked molecules must replicate together.
The origin of eukaryotes. The ancestors of mitochondria and chloroplasts were once free-living prokaryotes: today, they can replicate only within a host cell.
The origin of sex. The first eukaryotes could, presumably, reproduce asexually, and on their own: today, most eukaryotes can replicate only as part of a sexual population.
The origin of multicellular organisms. The cells of animals, plants and fungi are descended from single-celled protists, each of which could survive on its own: today, they exist (outside the laboratory) only as parts of larger organisms.
The origin of social groups. Individual ants, bees, wasps and termites can survive and transmit genes (either their own or ones genetically similar to their own) only as part of a social group: the same is effectively true of humans. …
CHAPTER 16
16.7 The origins of human society
A simple model
The peculiar thing about human society, as Gellner (1988) remarks, is that there is not one kind of society, but many. The problem for biologists, therefore, is to explain the evolution of those traits that make it possible for humans to live in a vast array of different societies. In this section, we describe a simple model— called, for obvious reasons, the Social Contract game … We do not regard this model as an adequate description of any human society. We use it for two purposes. First, it shows that rational beings can, at least in principle, defeat the Prisoner's Dilemma. Second, it provides a background for our later discussion of the fact that real societies are not exclusively, or even mainly, rational. …
… Logically, the contract is stable against defection. Although not an adequate model of any complete society, it is for some groups within society, such as the freemasons or the mafia. Clearly, the behaviour requires language, because the word 'cooperate' in the contract refers to some specific behaviour (e.g. not smoking in public buildings) that is not innate, but must be defined linguistically. The process whereby the contract is reached also requires a developed form of self- consciousness. Individuals must not only be concerned with their own future interests but they must recognize others as being individuals like themselves, with similar motivations: otherwise, why should one individual suppose he could persuade another to agree to the contract? Only organisms with language, and this level of self-consciousness, would be capable of negotiation leading to a contract.
The model has two major weaknesses. The first concerns the way in which cooperation is enforced, and the second the assumption that all individuals start out equal. First, consider enforcement. It is probably not true that most social behaviour is motivated by a fear of punishment. Often, the crucial factor is ritual. In Gellner's (1988) words:
The way in which you restrain people from doing a wide variety of things, not compatible with the social order of which they are members, is that you subject them to ritual. The process is simple: you make them dance round a totem pole until they are wild with excitement, and become jellies in the hysteria of collective frenzy: you enhance their emotional state by any device, by all the locally available audio-visual aids, drugs, dance, music, and so on: and once they are really high, you stamp upon their minds the typeof concept or notion to which they subsequently become enslaved.
It seems, then, that biologists have to explain not only the origin of language but also the capacity to be socialized by ritual. The content of ritual varies from society to society, and its importance relative to rational calculation and legal sanction may have diminished in the course of history (or perhaps we only hope that it will diminish), but all humans are influenced by it. This may be no great mystery. An individual who could not learn would be ostracized. But it is still unclear why the inculcation of proper behaviour is achieved by ritual and myth rather than by explicit precepts. Why Macbeth, and the biblical story of Cain and Abel, instead of, or as well as, the simple rule 'thou shalt not kill'? It is easy to say that ritual is effective in creating an emotional commitment to a set of beliefs, rather than a mere acceptance, but that is to describe a state of affairs rather than to explain it.
The innate capacity to be influenced by ritual may have been individually selected, although we are not clear why it should be so. But rituals, once formed, are culturally, not genetically, transmitted. Boyd & Richerson (1985) have suggested that between-group selection may have favoured rituals that are particularly effective in binding a group together. They are not suggesting that the content of a myth or ritual is genetically specified. Their point is, rather, that a culturally transmitted trait can also be selected. If a human group is successful because of its system of ritual, this has two effects: by cultural evolution, it causes the spread of a particular set of beliefs, and by genetic selection it favours individuals who can be strongly influenced by those beliefs (and probably by any other ritually enforced beliefs). In other words, there is between-group selection for culturally inherited systems of belief that favour the success of groups, and there is individual selection for the genetically inherited ability to be influenced by ritual.
A second weakness of the model lies in the assumption that all individuals are initially equal, and have the same strategy set open to them. In more complex societies this is clearly not so. Possession of land, factories or weapons alters the options available. The Marxist insistence that political ideology is determined by class position is clearly part of the truth. It is also easy to understand why social groups should acquire systems of myth and ritual: a group with such a system will be better able to defend the interests of its members. The persistence of historically shared myths is astonishing, and sometimes disastrous. Such group identities, within a larger community, are more relevant to the troubles of ex- isting societies than to their origins, but they do bear witness to the ease with which humans construct group identities, buttressed by ritual.
Theories of society
Theories of human society differ in two main ways:
Does society resemble a house or a termite mound? A termite mound differs from a house in that no individual has an image of the final structure, which, although highly functional, emerges from the interactions of millions of individuals, whose behaviour is law-governed but not influenced by any such image. In contrast, an architect starts with an image of the final building, which is functional because of his rational thought, and not through the naturally selected but blind behaviour of the builders. Does society resemble a house or a termite mound? Was its structure planned by a group of rational law-givers, as the constitution of the United States was planned by the founding fathers? Or is it merely the unplanned outcome of the behaviour, rational or otherwise, of its members?
Is individual behaviour determined by reason or ritual?
These two dichotomies define four theories of society, which we now describe. We have named them after four famous philosophers. No doubt we shall be accused of grossly oversimplifying their ideas. This is perhaps true, but it may be no bad thing. The trouble with theories of society is that their formulations are so lengthy and so complex that they are hard either to grasp or to test. Theories should be formulated briefly, even if the facts to which they are relevant must be described at length. The Origin of Species is a long book, but no biologist regards it as impossible to outline Darwin's theory in a few sentences. It is true that some mathematical theorems have proofs running to several hundred pages: in essence, the latter constitute theories associated with the theorems. But mathematical statements are unambiguous, and so permit long chains of argument. Unfortunately, statements about society, as about evolution, have a degree of ambiguity. It follows that theories in these fields, if they are to be operative in the sense of leading to clear predictions, must be simple.
Of course, it may be that no operative theories are possible in the social sciences. With this preliminary excuse, we offer the following classification:
Rousseau and the social contract. This is the model we have already discussed. Its essential features are that society is rationally planned, and that its maintenance depends on rational behaviour by its members.
Plato's republic. Plato's model of society is also a house rather than a termite mound. It is planned by a philosopher. It depends on a division between rulers, soldiers and labourers, which, for some odd reason, Plato calls 'justice'. But it is maintained by myth, not by the rational calculation of its members. With admirable frankness, Plato wrote in the Republic
How can we contrive one of those expedient falsehoods we were speaking of just now, one noble falsehood, which we may persuade the whole community, including the Rulers themselves, if possible, to accept? . . . All of you, we shall tell them, are brothers, but when God was fashioning those of you who are fit to rule, he mixed in some gold, so these are the most valuable, and he put silver in the auxiliaries, and iron and bronze in the farmers and other craftsmen. Since you are all akin, your children will mostly be like their parents . . . That is the story. Can you suggest any device by which we can get them to believe it?
In case there should be any doubt that it was ritual that should be used to ensure compliance, he wrote in the Laws:
All he [i.e. the legislator] needs to do is to find out what belief is most beneficial to the state, and then use all the resources at his command to ensure that throughout their lives, in speech, story and song, the people all sing to the same tune.
Durkheim's organic society. Durkheim's society is a termite mound. It is functional, but no-one planned it. It works because its members are influenced by ritual.
Adam Smith and the free market. Strictly, Smith's model is of the economy, not of the whole society, but perhaps, since his most famous recent practitioner announced ‘there is no such thing as society’, that need not worry us. His basic idea is that the economy works best, in producing the goods people want, if it is free rather than planned. Individuals do behave rationally, but in their own individual interests, with no image of the total result. It is a termite mound, not a house, but one maintained by rational calculation. The history of the last 40 years leave little doubt that he was right about the relative efficiencies of free and planned economies. The snag is that his truth is partial. It is profitable to discharge toxic wastes into rivers, and to market cigarettes and heroin.
Not all theories of society can so easily be forced into this Procrustean matrix. Kant's views are summarized in the following quotation:
The problem of organizing a state, however hard it may seem, can be solved even for a race of devils, if only they are intelligent. The problem is: given a multitude of rational beings requiring universal laws for their preservation, but each of whom is secretly inclined to exempt himself from them, to establish a constitution in such a way that, although their private intentions conflict, they check each other, with the result that their public conduct is the same as if they had no such intentions.
In other words, we need an architect who will so design the rules that individuals, each acting in their own best interests, will generate a socially desirable end. Society is a termite mound, in that its members do not envision the whole, but their behaviour has been planned by a designer so that they will generate the society he already envisions.
Thus in Kant's model, as in Rousseau's (at least, in the Social Contract model described above), individual behaviour is governed by rational self-interest. In both, there is also a need for a central planner, but in Kant's model, instead of laying down specific rules of behaviour, with punishment for transgressors, the central plan is confined to laying down the rules of interaction in such a way that rational self-interested behaviour leads to the common good. Adam Smith could have claimed that this is what he did, at least for the economy, by insisting that the market should be free, and not constrained.
Marx and Engels were, in this sense, Kantian. Marx's thesis ‘man's being determines his consciousness’ implies that an individual's behaviour is influenced by his own needs: it is a termite-mound model. But they argued that, if land and the means of production are publicly owned, it will pay individuals to act in a socially desirable way. The snag was that they did not allow for the free-rider, or did not foresee that state machinery intended to discipline the free-rider would develop into a new social class, governing in its own interests.
The ideas of Adam Smith and Karl Marx may be more relevant to our present political problems than to the origins of society. The Durkheimian view of a functional but unplanned society, governed by ritual, is closer to the picture of the earliest societies held by most anthropologists. Such a society requires individuals genetically capable of language, and of socialization by ritual. But this organic picture cannot be the whole story. Organisms function effectively only because natural selection has moulded the rules governing the behaviour of cells so as to produce a functional whole. How do ritual-governed societies become functional? After all, it is probably as easy to inculcate by ritual behaviours that are socially destructive. There seem to be two possible answers. One is that early societies became functional through the selective success of culturally inherited sets of beliefs. The alternative is that an element of rational calculation played a role in deciding which particular beliefs and practices would be enforced by ritual. Plato's legislator, inventing rituals to enforce his noble lie, is going too far, but those who elaborated myths and rituals may have given some thought to the social consequences of their inventions.
Origins
What can be deduced about the origins of human society from the fossil record and from comparative biology? … Our australopithecine ancestors adopted an upright posture at least 4 million years ago, long before there was any substantial increase in brain size. Australopithecines had ape-sized brains, about one-third the size of a modern human's. By the Homo erectus stage, the brain had doubled in size. Even so, the tools of Homo erectus were technically uninventive. Their most elaborate tool was the handaxe, fashioned from a single block of stone and worked on both surfaces. It was more innovative than any tool used by chimpanzees. Chimpanzees use hammerstones and anvils in the wild in some habitats: in captivity, they can be taught to make and use flint flakes.
It is a striking fact that handaxes, which first appeared about 1.5 million years ago, continued to be made for more than a million years. Only after the evolution of the earliest Homo sapiens, around 250 000 years ago, are there signs of slightly more skilled toolmaking and a more varied toolkit. However, tools and tool materials generally remained conservative, even after the appearance of fully modern, large-brained people around 100 000 years ago. The burst of technological innovation came relatively recently, only about 40,000 years ago.
It is hard to suppose, therefore, that the increase in brain size, by a factor of almost three, could have been a response to selection for improved technical skill. What selective force did lead to our larger brains? It is conceivable that the relevant factor was the evolution of language. It seems more likely, however, that language as we now know it evolved rather recently, and that it was responsible for the dramatic changes that have occurred in the past 100,000 years, not for the increase in brain size that took place earlier.
Dunbar (1992) has pointed out that, if one compares the forebrains of existing primates, the best predictor of brain development is the size of the social group in which an individual lives. He therefore suggests that the main selective force favouring increased intelligence in primates arises from social interactions. An individual who can act appropriately in a variety of social contexts will be fitter than one who cannot. Extending this argument to our own ancestors, the increase in brain size was an adaptation to living in society.
Half a million years ago, Homo erectus was distributed throughout the tropical and temperate regions of the Old World. This has led to a debate between those who think that existing human races evolved in situ from the local populations of H. erectus, and those who think that H. sapiens originated once only, probably in Africa (although that is not certain), and subsequently spread round the world, replacing the local populations of H. erectus. The latter view, of a single origin, has been greatly strengthened by molecular data. … We are left with the conclusion that we are descended from a rather small human population, probably living in Africa some 200 000 years ago.
This conclusion from the molecular data is consistent with the fossil and archaeological evidence. By 40,000 years ago, populations in Europe and else- where were producing a wide range of novel artefacts, were burying their dead, painting on the walls of caves, and engaging in trade. It seems that something happened to make possible both the geographic spread of H. sapiens, and the burst of new technical and cultural practices. The obvious candidate is the origin of human language. We discuss this, the last of the major transitions, in the next chapter.
CHAPTER 17
17.11 Conclusions
Evolution from apes to humans has involved both an increase in general cog- nitive ability, and in specific competence for language. The steady increase in brain size over the past 2 million years suggests that the increase in cognitive ability also proceeded over this period. The main selective advantages conferred were improved ability in the manufacture and use of tools, and in social skills. Already, in other primates, there is evidence of an association between brain size and the complexity of the social system, and this association was almost cer- tainly important in our own ancestors.
The timing of the origin of language is more difficult to determine. However, the dramatic increase in technical inventiveness during the past 40 000 years, discussed in the last chapter, is most readily explained if the final stages in linguistic competence emerged at that time. Humans differ from apes not only in grammatical competence, which has been the main topic of this chapter, but also in the ability to produce and perceive sounds. One difficulty in teaching apes to talk arises because they cannot make all the sounds used in human speech. Human evolution required both anatomical changes, and improvements in the brain mechanisms concerned with sound production and perception. Anatomically, the descent of the larynx in humans has increased the range of sounds we can make, at the cost of increasing the chance of choking when we eat or drink. It would be helpful if we could date this change from the fossil record, but anatomists are divided as to how far this is possible: unfortunately, the hyoid cartilage, which would provide the information, rarely fossilizes.
The changes in brain mechanisms are equally important. Although sound input is in principle a continuous variable, we unconsciously classify incoming speech sounds into discrete categories: in other words, we treat the input as digital. We are able to produce and to perceive sound 'segments' (roughly equivalent to the letters of the alphabet) at the astonishingly high rate of 25 per second. This rapid transmission is necessary: without it, we would forget the beginning of a sentence before reaching the end.
The emergence of human language, then, required changes in anatomy, in motor control, in sound perception, and in grammatical competence. These changes could not have been instantaneous, but may well have been rapid. They must have predated the dispersal of Homo sapiens throughout the world, most probably from Africa, because all existing human populations are alike in these respects. Subject to this constraint, however, the events may have been fairly recent.
This book has been about the major changes that have taken place in the way in which information is encoded, and transmitted between generations. The origin of language is the last transition of this kind that had a genetic basis, but it is not the last transition. The invention of writing made possible the emergence of modern, large-scale societies, and the change from societies dominated by magic and ritual to those in which science and reason play an increasing role. We are today in the midst of yet another major transition, to a society in which information is stored and transmitted electronically. It is impossible to foresee where this latest transition will lead. But the emergence of computer viruses may be a straw in the wind: we must beware that we are not replaced by a new kind of self-replicating entity.
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John Maynard Smith and Eors Szathmary, The Major Transitions in Evolution, Oxford University Press 1995
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