Who invented thinking?

When we see the extraordinary abilities and achievements of the homo sapiensit is difficult to avoid the impression that with a certain inevitability we became what we are. After all, the seductive thought goes that the product is human, such a miracle that it could only come at the end of a long and targeted process of improvement and improvement. How could we have become like this by accident? If we owe our outstanding status to evolution, it must have worked long and hard to refine and perfect its work.

Yet that's not the way evolution takes place. Natural selection in and of itself is not a creative process - yes, it cannot be. It can do nothing other than either favor or eliminate new traits that have arisen through accidental genetic changes. This process (which is of course influenced by what previously existed) forms the background of all biological innovations. Evolution can best be described as opportunistic: it merely uses or discards possibilities when and where they present themselves; one and the same option can be advantageous at one point and disadvantageous at another, depending on the respective environmental conditions (viewed in the broadest sense). There is nothing purposeful or inevitable in the evolutionary process. And nothing prevents him from simply turning around whenever the unsteady environment favors it.

What does our previous knowledge teach us about our ancestors? One of the most important findings is the insight into the meaning of what has been increasingly called "exaptation" in recent years. This term refers to traits that arise in one context, but are then used in a completely different one, and characterizes the spread of such innovations in populations.

The classic example of an exaptation that has become an adaptation (adaptation) are springs. Today they allow birds to fly. Millions of years ago, when only insects and dinosaurs could take to the skies, they obviously served a group of reptiles for thermal insulation (and before that maybe for nothing special). So, for a long time, springs were just very useful adaptations to keep body temperature constant. As flight aids, they remained mere exaptations until much later they also took on an adaptive function for this new ability. There are many comparable examples - enough, in any case, not to ignore the possibility that our outstanding cognitive abilities may have developed in a similar way to the feathers: as a much more insignificant trait, compared to their current role, which originally may have only been minimal Bringing benefit or just a by-product of something else.

When the first Cro-Magnon humans arrived in Europe some 40,000 years ago, it has been proven that they already brought with them the more or less complete repertoire of behaviors that distinguish modern humans from every other species that has ever existed. Sculptures, engravings, painting, body decoration, music, the use of abstract symbols, the expert handling of various materials, sophisticated burial rituals and filigree decorations of everyday objects - these and much more were integral parts of everyday life in the early days homo sapiens. Impressive evidence of this is provided by several sites in Europe that are more than 30,000 years old.

What connects all these behaviors most clearly is their common root in the ability to abstract, symbolic thinking. There can be little doubt that it was this fundamental characteristic, and not the acquisition of any of the listed (or unsaid) specific skills, that was behind the advent of "modern" elements in the behavioral repertoire of our ancestors. Even more: This new intellectual potential contrasts extremely starkly with the rather modest cultural achievements of the Neanderthals, who were at home in Europe and West Asia and were superseded by the newcomers astonishingly quickly. Undoubtedly, the behavior of the Cro-Magnons - like ours - was fundamentally different from that of all previously existing human species. It is absolutely no degradation of the Neanderthals (or any of the other now extinct human forms, whose knowledge and skills were absolutely admirable in their own way) to say that with the appearance of abstract thinking and symbolic action, modern homo sapiensmanifested a new level of being on earth. To explain how this came about is the most fascinating and confusing of all questions in biology.

One difficulty arises from the fact that there does not seem to be any connection between the emergence of modern behavior and anatomical modernity in human ancestry. There are indications that around 100,000 years ago in the Levant (Middle East) there were people who looked just like us morphologically. But in striking contrast to the events in Europe, the Neanderthals stayed in this area for 60,000 years after the appearance of anatomically modern humans. Also, during this long period of coexistence (whatever it was, and frankly we have no idea how these different hominids managed to share the territory over the millennia) the ways of life and behavior of the two early human species were more or less less identical; at least the tools they made and the archaeological sites studied so far suggest it. Apparently the Neanderthals only disappeared from this region around 45,000 years ago - exactly at the time when stone tools of the Cro-Magnon type first appeared in the Levant. So it was almost certainly the implementation of abstract mental abilities that gave our species the decisive - and for the Neanderthals fatal - head start. This almost forces us to conclude that the anatomically modern homo sapiensappeared on the scene much earlier than the modern human being in his behavior. While this may sound quite illogical at first (wouldn't it be much more plausible if the appearance of a new behavior coincided with the appearance of a new species of human being?), It really does make sense. Because where should new behaviors of whatever kind establish themselves, if not within an already existing species?

Brain volume and mental power

As a general rule, if you want to understand the mental performance of a vertebrate species, you should first look at its brain. In our own family, however, this is not very telling. Homo neanderthalensis had a brain the same size as ours. However, it was in a clearly differently shaped skull. While the diverse archaeological finds provide very precise information about the completely different behaviors of Neanderthals and Cro-Magnons, brain specialists find it difficult to identify any structures on the surface of the brain in casts from the skulls of the two hominid species that indicate an important functional Could indicate a difference. Accordingly, the emergence of higher mental abilities cannot simply be viewed as the culmination of a gradual increase in the efficiency of the brain. Something else happened than a final physical tuning of the thinking apparatus. Of course, when the modern-looking human took the world stage, the foundation stone had to be laid for the realization of advanced cognitive processes. However, this does not mean that a specific neural mechanism for these processes already exists.

At this point it should be expressly reminded that new structures are not targeted Forsomething specific arise. They arise accidentally as by-products of copying errors that occur constantly when the genetic material is passed on from generation to generation. Natural selection is certainly not a creative force that naturally brings new structures into being. It can only start with given variants, which it then either eliminates as disadvantageous or promotes as favorable.

We like to talk about adaptations, as this helps explain how and why certain innovations have appeared and prevailed in the course of evolution. But in truth, all new genetic variants must have arisen as exaptations. The difference between the two is elementary: while adaptations are features that fulfill specific and clearly definable functions (which they can of course only be able to do as soon as they exist), exaptations are merely features that have arisen spontaneously and are initially only potentially used Are available to take on a new function in the further course of development. This is a common phenomenon because many new biological structures are preserved for no other reason than not to disturb them further.

In this context we must clearly distinguish between two things: on the one hand, the evolution of the human brain into the organ we are familiar with, and on the other hand, the emergence of advanced mental abilities. There is no doubt that the average brain volume has increased over the past two million years; but that doesn't say much about how our minds actually evolved. The example of the Neanderthals and (perhaps even more) who teaches modern humans anatomically but not yet in their behavior that outstanding cognitive abilities do not simply arise from an extra portion of gray cells - as if only one last ounce of brain mass was needed to transcend existing spiritual boundaries. The formation of any important new brain structures cannot have played a role either, since the structure of the brain in all higher primates is remarkably similar in its basic features. Instead, an exaptized organ, endowed who-knows-when with a neglected potential for abstract thinking, was suddenly used one day for what is its real strength.

Unfortunately, it is so far in the dark what exactly has given the brain the potential for demanding intellectual activities. This is largely due to the fact that although we know a lot about the structure of this organ and which brain regions are active in performing certain tasks, we have no idea how the brain converts the vast amounts of electronic and chemical signals into what we commonly understand by consciousness or thought patterns. But figuring this out is crucial if we ever really want to understand what it means to be a (I use the term wisely) a being gifted with reason.

Dormant potential

However, it is possible to speak on a general level about the evolution of the human mind. For example, one common theory is that at some point - perhaps 60,000 to 50,000 years ago - a species appeared in human ancestry that possessed the novel ability to express symbolically. Accordingly, this new species should have had a modified brain that allowed modern behavior patterns. It would be nice to believe that because it would in some ways simplify the problem. But there was simply not enough time for this scenario. If the explanation were correct, a new human species, physically identical to an existing one, but intellectually superior to it, would have emerged, spreading across the entire Old World in an incredibly short time, completely wiping out its predecessor species. But there is absolutely no evidence in the - admittedly incomplete - series of archaeological evidence from this time that something like this could have happened. Obviously there is only one alternative left.

Perhaps rather than looking for some anatomical innovation, we should look for some kind of cultural trigger for the genesis of our extraordinary minds. If the modern human brain with all its possibilities, together with the modern skull shape, arose around 150,000 to 100,000 years ago, it could have existed as an exaptation for a considerable time, while the neural structures initially continued to work in the previous way. Unfortunately, the testimonials are direct information about the origin and distribution of the homo sapiensdeliver, far more sparsely than we would like. At least we know that our species appeared around the same period, presumably in Africa. And we also know that the homo sapiensfrom its place of origin (wherever it was exactly) spread fairly quickly across the Old World.

If at some point, say 70,000 to 60,000 years ago, there was a cultural innovation in any human population that activated the long-dormant potential for abstract thinking in the human brain, the rapid diffusion of symbolic actions can be effortlessly carried out through the simple mechanism of cultural Explain tradition. It is far more convincing (and certainly more satisfying) to note that the new behaviors spread very rapidly in populations that were already ready to adopt them than to assume that the global spread of unique human abilities will increase through a full population exchange Stand came. What a bloodbath that would have meant! In contrast, the cultural exchange between human populations has been documented many times in history and obviously provides the most plausible explanation for the rapid success of symbolically mediated human behavior. However, there is still no plausible answer to the question of what the triggering cultural innovation could have been.

Awareness and symbolic thinking

When we speak of "symbolic processes" in the brain or in thinking, we are referring to our ability to abstract details of our experience and express them through mental symbols. Certainly other species are also conscious in a certain sense, but as far as we know, they just live in the world as it appears to them. Presumably, their surroundings appear to them largely as a continuum and not, as we humans do, as a place that breaks down into a multitude of individual elements to which we give individual names. By separating components in this way, we are able to recreate the world and individual aspects of it in our consciousness over and over again. The prerequisite for this is our ability to create and handle spiritual symbols for things that we perceive in and around us. Representatives of other species often show a highly developed ability to reason intuitively, so that they can react to environmental stimuli in quite complex ways. But only humans are able to combine and reconnect spiritual symbols at will and to ask themselves questions like "What if?" It is on this ability that our highly acclaimed creativity is based.

Of course, intuition is still a cornerstone of our judgment. The abstract mind only came along. For example, an intuitive grasp of the relationships between objects and ideas is almost certainly just as important as the symbolic representation of connections as a prerequisite for scientific creativity. Ultimately, it is the unique combination of both that makes science, art or technology possible in the first place. Undoubtedly, a living being can achieve a lot with intuitive reasoning on its own. It seems to me that the Neanderthals prove that. In their rich archaeological legacy, there are only extremely meager references to abstract skills; Symbols obviously did not have a lot of place in their existence. Nevertheless, their achievements appear extremely remarkable. As far as can be judged, they ruled nature better than any of their predecessors in human history. One has to admit, without envy, that with their purely intuitive abilities they have reached the most complex way of life that should be possible on this basis.

That inevitably begs the question the answer to which everyone would like to know: Could the Neanderthals speak? Many of us hardly want to believe - especially in view of the sophisticated stone tools that the Neanderthals made with so much skill - that they did not have language. How could such remarkable skills have been passed on from one generation to the next, if not through language?

Not long ago, a Japanese team of researchers made a first attempt to answer this question. It divided a number of students into two groups. One taught by archaeologists by means of detailed verbal explanations in connection with practical demonstrations how to make a typical Ne-Andertaler stone tool.The other group was only shown the technique without a word. The experiment made one thing blatantly clear: how difficult it is to make stone tools; some subjects never learned. What was even more remarkable, however, was that there was virtually no difference in the results between the two groups - neither in the speed with which the students acquired the skill they were taught nor in the skill they showed in the end. Obviously, to pass on sophisticated manufacturing techniques for stone tools, mute demonstration is completely sufficient.

Although today's people and not Neanderthals took part in this experiment, the result shows once again what a fundamental error it is to assume that our type of communication is the only effective one. This is not to say, of course, that the Neanderthals did not have any form of phonetic communication; perhaps it was even quite differentiated. After all, communicating by means of vocalizations is common practice among vertebrates. There can be little doubt that the Neanderthals spoke in a general sense. What they almost certainly did not know, however, was language in the form we are familiar with today.

Language and Emergence of the Human Mind

If one were to name one aspect of human mental activity which, more than any other, is related to symbolic processes, that would surely be our use of language. It is undoubtedly the brain function with the highest degree of abstraction. Without it, thinking as we know it seems simply unimaginable; because words function as the basic building blocks of our conscious thoughts and deliberations. They are the medium with which we communicate our ideas to other people and - as highly social beings - try to influence what goes on in their heads. So if we are looking for a particular cultural trigger that opened the door to symbolic thinking, then the invention of language is the most obvious candidate. Yes, it may even be the only plausible one that has been tracked down so far.

What could have happened The term exaptation provides the key to a deeper understanding; because language is a unique means of communication, which apparently did not develop from an "original language" already rudimentary in monkeys and certainly did not develop directly. Nevertheless, scientists have held the view that the general ability to acquire language is so deeply and universally anchored in the human psyche that there must be hard wiring in every regular brain, based on the "normal" Darwinian principle of adaptation through natural selection .

Of course, the language is not reinvented in every generation, but it has to be acquired again and again: Learning the mother tongue (s) is a natural, albeit astonishing part of the developmental process that every child goes through as they grow up. In other words, the existence of a "language instinct" in humans cannot be denied. What needs to be explained, however, is not only how this innate predisposition came about, but also how it could appear so quickly and suddenly.

We have seen that natural selection is not a creative force and cannot create anything on its own, but can only capitalize on what already exists. In a sense, it makes things easier because, as far as we can tell, there is no evidence that the ability to think abstractly was the end result of the slow development one would expect from Darwinian selection. Instead, after a long - and still hardly understood - period of aimless enlargement and rearrangement of the brain in the human line of ancestors, something must have emerged that paved the way for the acquisition of language. This innovation could only be based on the phenomenon of emergence, where a random combination of pre-existing elements produces something completely unexpected. The classic example of an emergent quality is water; most of its special properties are completely unpredictable when looking at the behavior of its building blocks hydrogen and oxygen. The combination of these elements results in something completely new that can only be explained in retrospect. In connection with the exaptation, the emergence forms a powerful evolutionary mechanism - a real driving force that steers accidental innovations in new directions.

In the case of the innate speech faculties of all humans today, it can be assumed that some neural mechanism changed at the beginning of some population in the human ancestral line. From a genetic point of view, this change was probably rather minor and probably had nothing to do with adaptation in the classical sense. Since the brain structures itself during early childhood development through the formation of specific signaling pathways from an undifferentiated mass of randomly linked nerve cells, this event may even be based on developmental stimuli and thus took place on the epigenetic instead of the genetic level. However, it does not appear to have left any traces in any fossils, although its impact on the archaeological evidence of the Cro-Magnons and their descendants was ultimately enormous.

Reshaping of the pharynx

Just as the keystone in a round arch is only an inconspicuous part of the overall structure, but contributes decisively to its stability, this innovation (whatever it may have been; and we are still far from understanding it) was the final physical component, which first had to exist in order to enable language and symbolic thinking - as well as everything that grew out of it with such fateful consequences for the world. Once this innovation had occurred, the potential it contained could lie fallow without causing harm until it was activated by a cultural stimulus within a certain population.

Almost certainly that impetus was the invention of language, even if that is difficult to prove. Each of us can speak today, which in itself shows how extremely beneficial this achievement must have been. And if it was as beneficial as we like to believe, it is hardly surprising that language, including the associated, symbol-oriented behavioral patterns, was able to spread very quickly in the human population as a result.

How exactly this fateful innovation was invented is another question about which to speculate is beyond my professional competence. But once the neural ground was prepared for language, it can have arisen in many ways. The variant I prefer is that an archetype was not invented by adults, but by children. In view of the fact that the brain is not a static structure like a rubber ball, but a dynamic unit that constantly reorganizes itself during adolescence (and even throughout life, given suitable stimuli), the idea does not seem so absurd, that a rudimentary forerunner of the language as we know it today started out in a playful way in a group of children. Such a preform may have consisted of sounds or words that acquired additional meaning when they were strung together. It is hard to imagine that once this invention was made, it would not have been taken up by society as a whole.

An example from the animal kingdom may illustrate this. On a Japanese island, researchers used to feed macaques living on the beach with thrown sweet potatoes. When the animals picked up the delicacies, there was usually a lot of sand stuck to them. After a short time, young monkeys began to wash it off in the sea. And after a while the adult animals followed suit: first the females and lastly the dominant males. Only a few older, particularly high-ranking patriarchs never condescended to this newfangled behavior and stuck to the usual sandy diet. But a good idea is a good idea - and it is difficult to believe that in the case of language the principle is the same Associating words with objects and ideas would not have spread to society fairly quickly once it was discovered.

Nevertheless, the transition from a non-verbal way of life to the familiar life with language meant a huge spiritual and practical leap. Presumably the syntax with its rules for the construction of whole sentences arose in a separate, later step, which was perhaps inevitably given by the creation of word-object connections. In general, the assumption would be rather implausible that the development from inarticulate to well-defined language, as we know it, took place all at once.

A multi-stage process, similar to the steps in which children learn language, seems much more plausible: it starts with building a vocabulary very quickly, then learning syntax rules and finally the correct formation of whole, well-structured sentences. The emergence of language was undoubtedly a very complicated process - so complicated that, from our point of view, it might seem impossible if we weren't would know that it took place. Of course, the language has changed a lot since its invention, has become far more complex and differentiated, while it began its triumphal march in humanity. Nevertheless, today it has a common basic structure everywhere, regardless of the respective culture. This can only be due to the fact that long before language itself emerged, the basis for it was laid in every anatomically modern human being.

But there is another factor to explain. To be able to speak, you need a brain that tells the speaking apparatus what to do. Equally important, however, is a speaking machine that can follow instructions from the brain. The primates' original vocal tract is in no way suitable for this. Indeed, humans are the only living things that are physically capable of making the sounds required for an articulated language (although some birds can imitate language).

This ability comes at a price. The speaking apparatus consists of the larynx and vocal cords, the overlying tubular pharynx, which opens to the mouth and nasal cavities, and finally the tongue with the surrounding structures. The vocal cords produce basic sounds that are modified in the pharynx and in the subsequent airways. Typically, in mammals, including the great apes - and even in human infants - the larynx is located in the upper neck area, which shortens the pharynx and thus limits the possibilities for modifying vocal sounds. In contrast, in adults, the larynx lies deeper in the throat; the resulting lengthened pharynx creates the conditions for better sound modulation. This enables a wide range of sounds and tones, but the price already mentioned is that it makes breathing and swallowing impossible at the same time - with the fatal risk of suffocating while eating.

That alone shows that the special design of the human vocal tract had to offer another distinct advantage to compensate. Unfortunately, that is not the ability to speak. From where I know this? Well, the "roof" of our vocal tract also forms the base of the skull. Therefore, in fossil finds in which this skull area has been preserved, we can roughly reconstruct what the respective sound-forming apparatus looked like during its lifetime.

The combination of a deep larynx and a long throat is revealed by the curvature of the base of the skull. The first signs of this can be found at almost two million years ago Homo ergaster; the skull also occupies one Homo heidelbergensis from Ethiopia that the skull base had practically reached its current degree of curvature around 600,000 years ago. According to this, a vocal apparatus had already been developed at that time that enabled its wearers to produce sounds for articulated language - more than half a million years before there was other, independent evidence that our ancestors spoke or used something like language.

The vocal apparatus of the adult cannot originally have been an adaptation that served speaking in today's sense, although it may have been advantageous for a "prelingual" form of phonetic understanding. Then what was it good for?

That inevitably brings us back to the concept of exaptation. Despite its drawbacks, a curvature of the base of the skull developed and persisted for a very long time before it was put into the service of language. Perhaps during this long period it really did favor the development of certain archaic forms of language - forms that we can hardly characterize in more detail. Or maybe it brought some breathing benefit - a point that has hardly been explored in extinct hominid species. However, the conclusion remains that the appearance of language and the anatomical changes associated with it were initially not the result of natural selection, even if in retrospect they have proven to be highly beneficial.

At the moment we don't have the slightest chance of explaining even remotely convincing how we became the extraordinary beings that we are without resorting to the inconspicuous mechanism of exaptation. We are certainly not the result of a steady, refined process of refinement over tens of thousands of years. Much of our history has been a series of fortunate coincidences. Nature has never "intended" to promote us to the dominant position within the realm of organisms in which we find ourselves - for whatever reason - today.

To a high degree we are just random travelers, on wondrous paths in the realm of nature. But of course that doesn't make us any less remarkable. And we are even less free of responsibility because of this.

The article is a slightly abbreviated excerpt from the book "The Monkey in the Mirror" by Ian Tattersall, recently published by Harcourt Inc.

From: Spektrum der Wissenschaft 4/2002, page 56
© Spektrum der Wissenschaft Verlagsgesellschaft mbH

This article is included in Spectrum of Science 4/2002