Human evolution is a multidisciplinary problem, one of its aspects is the origin and development of distinctively human psychological features. Cognitive properties (language, symbolic thinking) are considered as such features and numerous authors hypothesize its evolution. We suggest that the most important human characteristic is connected with motivation rather than cognition; this is the ability to construct and maintain long-term goal-directed processes having no biological basis. Once emerged, this new ability determined evolution. Human language arose from the need to subserve group activities directed at achieving long-term goals. Abstract thinking resulted from the extraction of nonperceptual features through the regular and purposive usage of various objects. The comparison of this hypothesis against other evolutionary models is discussed.
Key words: evolution, social, motivation, language, symbolic thinking
The evolution of human beings is one of the most interesting problems in contemporary science. Various disciplines offer different approaches to the solution of this multidisciplinary problem. One of the approaches is devised by psychology, it is necessary to determine distinctively human psychological features and to understand its origin and development in the process of evolution. The first part of this project seems to require minimal efforts because each layperson is undoubtedly able to determine distinctively human psychological features such as language, concepts, or rationality. It is not difficult to notice that these properties can be considered as certain aspects of human cognition and this meets the idea which seems obvious, that it is certain features of cognition that are distinctive human beings from other animals. Hence, human evolution is the evolution of human cognition, and there is only the problem of the origin and development of certain cognitive properties especially such as language or symbolic thinking. As a result, one can find out numerous works devoted to the origin and evolution of human cognition. Most of them can be attributed to the origin of language (Pinker, Bloom, 1990; Dunbar, 1993; Crow, 2000; Place, 2000; Corbalis, 2003; Arbib, 2005 among others), because the faculty of language seems the most specific psychological feature of humans. Some authors try to describe how symbolic thinking or such its attributes as counting or drawing could have emerged and evolved (Sheets-Johnstone, 1994; Donald, 1991; Gabora, 1999 among others) . However, even discounted the insufficiency of archeological records, such models do not seem convincing, the true factors underlying the emergence and development of uniquely human features seem absent in them (Chomsky, 1988; Lucas, 1999).
Indeed, one of the most serious problems for the various models of human evolution is the necessity to explain the redundancy of human cognition (Pinker,Bloom, 1990; Chomsky, 1988). For example, the complexity of language seems redundant for the living and survival of ancient hominids and the very primitive language of chimpanzee, which includes about 35 signals (Calvin, 1993), seems a good confirmation for this thesis.
Another aspect of this problem is the universality of human beings. Humans are the only mammals able to live in virtually any environment from Siberia to Sahara. It is not clear how this remarkable characteristic could emerge. If our ancestors lived in a stable environment then they must have adapted to this environment but not to other circumstances (and great apes occupy very limited niches). On the other hand, if our ancestors evolved in very unstable environments (Calvin, 2001) then their redundancy might have gradually decreased because with the limitation of the resources of any organism, evolution may prefer organisms with few characteristics invariant with respect to the diversity of circumstances rather than organisms having special adaptations to each sort of possible circumstances. Indeed, some microbes which are practically omnipresent are, undoubtedly, more primitive than any mammals.
Single mutations seem a solution for these problems. For example, some theorists suggest that language emerged randomly as a result of a single mutation (Crow, 2000; Corbalis, 2003) because they find no appropriate explanation for its appearance. Single mutations were probably important in human evolution but the consideration of this process as a consequence of random mutations not determined by ongoing selection makes human evolution practically unknowable.
A hypothesis on the role of motivation
Most models of human evolution seem to be based on obvious but, to some extent, narrow distinctive human characteristics and this is likely an obstacle to understand the process of evolution. A more general approach may be useful. In our opinion, any organism can be considered as a goal-directed system. The goal component of this system are all long-term states which the organism should achieve or leave unchanged in order to provide survival and reproduction. And to achieve these fundamental goals the means component, which is responsible for the formation and usage of diverse methods adjusting the organism to the environment is necessary. From this position, intelligence, language, tool making, which are, to some extent, used by animals are means subserving the adjustment to the environment and the achievement of fundamental goals
In psychological terms, the system of motivations corresponds to the goal component and the cognitive and motor systems underlie the means one. The emphasis of evolutionary models on cognition and, accordingly, on means without considering the role of fundamental goals or motivation seems a serious lack of such models. In our position, it is necessary to determine distinctively human characteristics of motivation and understand their influence on evolution.
The term ‘motivation’ means hereinafter all stable and long-term factors which activate and direct human actions. So, motivation includes not only hunger or sex but also career preferences, social attitudes, stable moral dispositions, and other often life-range goals conditioned by social interactions with other people. Though language and rational thinking are heavily involved in the formation of social long-term motivations, these mechanisms itself cannot provide the stability and purposefulness of long-term social motivations. For example, language and abstract thinking are absolutely necessary prerequisites for becoming some people as specialists involved in studying human evolution but the fact that the scientists can feel such emotions as curiosity, admiration, or frustration regarding certain facts from archeology and paleontology but do not have similar feelings regarding certain data from mathematics or astronomy and these emotions direct their actions for decades results from motivation rather than from cognition (Hekhausen, 1980; Leont’ev, 1979).
It is necessary to note that there are fundamental distinctions between the human and nonhuman systems of motivation. Animals are active only if their innate drives and emotions are activated, otherwise when the situation is neither novel nor dangerous, the animal is passive because all its needs are satisfied. Innate drives and emotions energize the behavior of animals and also direct this, i.e. through the system of reward/punishment they determine what stimuli are appropriate for satisfying the drive. People are able to control innate motivations because they have a stable hierarchy of long-term learned motivations. Animals also have long-term motivations (e.g., sex, hunger, and thirst), but these are all innate. An animal can form learned motivations, but only when one of the basic motivations is activated . The hypothesis that the motivation of animals is always constrained by basic drives was suggested by a German psychologist Kohler in 1917 (Kohler, 1917) and despite decades of research there have still been no data inconsistent with it (Suddendorf&Corballis, 1997) . So, unlike human beings whose activity lies preferably beyond the system of innate motivations, the behavior of animals is always within the system.
With this very serious distinction of human motivations from those in animals, it is important to understand the role of motivation in evolution. Because the system of motivations determines all activities of an organism including the usage of such means as language or thinking, we suggest the fact that human motivations are not constrained by innate mechanisms is the most important quality distinguishing humans from other animals. And our main idea is that human evolution started from changes in the system of goals. This means the emergence of the ability to construct and maintain long-term goals with no innate basis (Prudkov, 1999a, 1999b, 2005). These changes were likely a result of a mutation but on the other hand, they met a tendency of the complication in the goal-directed behavior of animals which is obvious in evolution (Byrne, 2000).
The emergence of this new ability was a real revolution in the processes of adaptation. Prior to this, the process of adaptation to environmental changes was very slow usually requiring modifications at the genetic level because behavior was seriously constrained by fundamental innate motivations which were determined genetically. Now, the adaptation could be established more rapidly at the level of phenotype, because behavior became more independent of innate motivations and, therefore novel long-term goals could rapidly be invented by a single organism and spread through communication and imitation. As a result, changes in cognition became necessary to provide pursuing such new goals and selection was directed at the maximization of such cognitive changes. Afterwards, these changes could, in turn, lead to novel complications in the goal-directed system.
It is reasonable to think then that human evolution can be described by a hypothesis of alternation between motivation and cognition. This suggests that the changes in motivation at a certain stage of evolution resulted in alters in cognition at the following stage (probably motivation also developed at this stage but less intensively) and vice versa. At each of the corresponding stages cognitive skills became more complex and diverse or motivational goals more long-term and drive-independent. This gradual complication of motivation and cognition conditioned by its interactions rather than by environmental changes seems an effective solution to the problems of redundancy and universality. This complex coevolution of motivation and cognition brought about the result that these components are strongly entwined in human behavior and therefore it is difficult to recognize their special roles.
We suggest that the evolution of hominids started when the goal-directed system of our ancestors became able to sustain and direct its own activity for relatively long periods even when the level of innate motivations was low. This means that the system could form a long-term chain of behaviors having an own source of activation and a goal not aimed at the satisfaction of drives, though such primary processes were, of course, connected with the prior activation of one of the drives. Since pursuing practically any goal require reaching many subgoals, the capacity to construct and maintain complex hierarchical processes with feedback was increased also.
Origin of language and abstract thinking
The weakening of innate constrains influenced all aspects of the behavior of first hominids. New methods of tool-making, communication, hunting became evolving thus resulting in cognitive achievements. We will try to describe the origin of two main features of human cognition such as the faculty of language and abstract thinking.
Language is a means of communication for organisms engaged in a joint activity and the complexity of a language must reflect the complexity and diversity of the activities in which the language is used. For example, modern languages such as English, Russian or Arabic consist of hundreds of thousands of words only because these languages are applied in thousands of diverse activities having accordingly various goals. The languages of hunter-gatherers were probably limited to hundreds of words (Vedenov, 1988) because the diversity of their goals was accordingly small. A fundamental distinction between human and animals languages is that the repertoire of nonhuman communicative systems is fixed. In our opinion, this is a reflection of the fact the diversity of animal activities is limited by the closed system of innate motivations and therefore animals are only needed a limited set of signals to communicate. Since all their motivations are connected with vital functions, any serious misunderstanding in the process of communication can be fatal; as a result, the number of signals in animal languages must be limited and the signals must have unequivocal meanings.
As a result, one can hypothesize that human language emerged because the group activities of early humans such as hunting or collective self-defense when under attack by other groups became complex and diverse enough owing to changes in the goal-directed system (Prudkov, 2005). As pointed out above changes in activities inevitably influence the language subserving the activities and the same mechanism must have caused the communicative skills (not only language but also the theory of mind and imitation) of early humans. For instance, when a group of early hominids participated in such long-term an activity, the members formed new signals by altering innate ones, and used them in interactions important for achieving certain goals. Inevitable misunderstandings were not critical because most of these goals were only intermediate and interchangeable. On the other hand, after frequent repetitions, some effective signals could be shared by the entire group, thus keeping their meanings constant for long periods. As a result, these novel signals with variable meanings could be a basis for the appearance of human language. Such a primitive language was, of course, considerably distinctive from modern languages but it could evolve on the basis of the hypothesis of alternation because the use of this language resulted in the complication of goal-directed activities leading, in turn, to the development of language.
The origin of syntax seems mysterious for many models of language evolution but this problem can be solved if one is aware of the fact that the construction of an utterance is simply a hierarchical process. The meaning of the utterance is the highest level in this hierarchy and the generation of syntactical trees, choice of a noun or verb, the account of necessary grammatical rules, prosody, etc. can be considered as subprocesses in this hierarchy connected via feedback loops. It is reasonable to assume that the complication of long-term hierarchical processes could result in the development of rapid ones such as those processes which underlie syntax (Bridgeman, 1992).
The main property of human thinking is its abstractness, i.e. humans are able to determine features of the objects invariant with respect to perceptive cues ( for example, long or short, red or green, wood or metallic objects all can be related to the category ‘stick’) and to apply these features in diverse mental and physical operations. In our opinion, there are two reasons why the ability to form and pursue long-term learned goals resulted in the abstractness of human thinking. Fist, if the motivation system of an organism is constrained innately then the organism is able to recognize the characteristics of the environment only which are important for achieving the innate goals because the recognition of any other qualities is unnecessary for survival and reproduction. Of course, if the system of motivations is sufficiently complex, the repertoire of recognized characteristics can be very wide but nevertheless, it tends to be limited. And second, only the long-term participation in diverse activities allows selecting the characteristics of objects invariant with respect to these activities (Prudkov, 1999b).
It seems reasonable to suggest that first concepts were, presumably, a result of the manual activity of ancient humans. For example, it is difficult for apes to use sticks because they consider the stick as a set of visual features (long, thin, bright) and can use it only if some of the features fit the iconic representation of the problem. A high level of brain activity underlies the behavior of the chimpanzee when the animal integrates a certain property of the stick (its length, for example) with the problem (how to reach for the apple). With advanced motor skills and the ability to long-term activity, ancient humans could use sticks and branches as tools more often and for relatively long periods. After regular use in different situations, the present need to use a stick led to the simultaneous activation of numerous neural patterns connected with prior use of sticks. By overlapping those patterns, a new representation, invariant with respect to diverse visual features and situations, was constructed in the brain of an early man. This was the first concept, the concept of ‘stick.’ Now the early man became able, for example, to store sticks for another day, the action is unavailable for apes. Other long-term processes could, also, result in other concepts.
Modern humans as a consequence of motivational changes
As mentioned above, human evolution can probably be hypothesized as a consequential alternation of changes in motivation and cognition. Contemporary archeological records do not seem sufficient to reject or accept this hypothesis, however, one can assume that the last stage of human evolution (modern humans) resulted from motivational changes. First, some data from human ontogeny favor such an assumption. Indeed, children have acquired a native language by 5, the ability to think formally (Piaget’s stage of formal thinking) by 12 and they have became sexually active at 15. However, human maturation is not completed at 15 because long-term motivations which determine career preferences, social attitudes, stable moral dispositions, appear usually after 15 (Kon, 1979, 1980).
Second, the distinctions among humans in regard with long-term motivation exceed cognitive ones. For example, the inability to acquire a native language or to think formally are obvious characteristics of deficiency. Regarding motivation, the activity of most people is determined by interactions between innate drives and social stereotypes. Another pole, however, is the small part whose actions are defined by long-term goals often unsusceptible to social influences and even innate mechanisms (celibacy, political hunger-strikes as examples of this insusceptibility). And the absence of such goals is not a deficiency.
These facts, in our opinion, mean that the modern level of long-term motivation is a relatively late achievement of evolution, later than language or formal intelligence. It seems reasonable to think that a more efficacy in forming and pursuing long-term goals was the main advantage of modern humans over Neanderthals because the motor and cognitive possibilities of Neanderthals were likely similar to those of modern humans (Niewoehner et al, 2003).
The hypothesis given is that the ability to construct and maintain long-term goal-directed processes emerged early in human evolution and determined the development of cognition. A competitive hypothesis is likely that changes in cognition preceded those in motivation and defined the latter. For example, Tomasello et al. (Tomasello et al, 2005) suggest that human evolution started when ancient hominids became more amicable and domesticated than chimpanzees and as a result, they formed a special ability to participate with others in collaborative activities. This cognitive ability might underlie language and theory of mind because this was the basis for the group actions in which language and theory of mind could evolve. Arbib (Arbib, 2005) derives the origin of language from the emergence of complex imitation and then language appeared because imitating actions each other well, ancient hominids became able to communicate effectively. Though such models do not consider the origin of distinctively human motivation they may explain it as a consequence of late brain complication. The appearance of distinctively human motivation at a late stage can be considered as a solution to the problems of redundancy and universality.
However, the emphasis on changes in cognition conditioned by the complication in social contacts seems insufficient to explain the movement of human evolution towards maximum purposefulness and intelligence. Indeed, the result of changes in sociality and communication can be more cooperative and talkative organisms but it is not necessarily that they must be very intelligent or good toolmakers (Byrne, 2000). For example, bonobos are less aggressive and more domesticated than chimpanzees but bonobos are even less intensive in the usage of tools in the wild than their larger relatives (Wall de, 1995). It seems that selection directed at the maximization of even such complex but special features as cooperation or imitation is unable to construct such a general-purpose system as human beings. Only the formation of the ability to construct learned long-term goals resulting in the diversity of activities seems a reliable way to reach human flexibility. And this formation must have took place very early in human evolution because several stages of evolution are obviously needed to construct the ability to pursue arbitrary goals for decades using complex language and abstract thinking.
This, however, does not mean the impossibility of the existence of such species whose cognitive possibilities exceeded those of modern apes but their behavior was constrained by innate motivations. In our opinion, with the inability to long-term learned actions, such species must be considered as a deadlock direction of evolution.
The fact that humans and animals do something because they are motivated to do this is so taken for granted that most models of human evolution seem to neglect it. However this position is hardly correct. For example, the usage of various objects as tools is available for animals because this can directly results in the satisfaction of a basic drive but animals do not manufacture tools for subsequent use because this process is not aimed directly at drive satisfaction though the fact that apes are able to plan a complex sequence of actions (Byrne, 2003) means their intelligence is sufficient to manufacture tools, in principle. As a result, a certain level of drive-independent motivation was necessary to provide the regular manufacture of tools by our ancestors. This example demonstrates the necessity to take into account the role of motivation for understanding human evolution.
We suggest that long-term learned motivation is the most important characteristic distinctive humans from other animals whose motivation is always constrained innately. Since motivation determines the usage of cognition, the cognition of animals must be more primitive than that of humans. Roughly speaking, animals have not cognitive possibilities (language, thinking) similar to those of humans simply because they do not need it.
One can assume that human evolution started when our ancestors became able to construct and maintain goals not motivated directly by innate mechanisms for relatively long periods. This meant that behavior became more complex and purposeful. Cognitive skills elicited by these new motivations became more diverse and flexible, as result, those ancient hominids that were effective in the construction and acquisition of such skills could succeed in reproduction. Novel hominids whose abilities to think, communicate, make tools exceeded those of their predecessors became able, in turn, to construct and pursue more complex, long-term and drive-independent goals. So, the interaction between motivation and cognition was, in our opinion, a basic factor underlying human evolution, while the adaptation to environmental changes played a subordinate role. This mechanism allows to understand why humans have a potential which seems redundant for living as hunters-gatherers, and why they are able to survive under any circumstances.
Of course, this approach like any other evolutionary models is speculative enough and can simply be considered as a just-so story. With the shortage of archeological data, there are serious chances that no evolutionary models will be accepted as absolutely correct at all. However, it seems obvious that the understanding of the real mechanisms of evolution can be achieved only on the basis of taking as many facts and assumptions as possible into account. And the model suggested seems an useful step to this direction.
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