Origins of Psychedelia
The search for evidence that human tribes and societies throughout global history have used psychoactive plants for religious, shamanic, philosophical and medical purposes
Gosso & Webster — Dream on the Rock, chapter IV — pre-publication version
The Most Human Universal
The search for evidence that human tribes and societies throughout global history have used psychoactive plants for religious, shamanic, philosophical and medical purposes has met with great success. Publications citing such evidence come from an entire spectrum, from drug-use oriented screeds to the most conservative of scientific journals. The ultra-respectable Scientific American Library Series counts among its handsome and lavishly illustrated volumes its Plants, People, and Culture — The Science of Ethnobotany, and devotes an entire chapter to plants that have been used for “Entering the Other World”. A world map shows clearly just how universal psychoactive plant use has been, the historical locations of use of a dozen of the major plant species being shown across the globe.[1]
The science of anthropology has not always been at the forefront of such research however, and still today some of the reigning paradigms of the discipline reveal a willful ignorance of the importance of psychoactive use in the evolution of human societies. Many examples could be cited, but one especially concerns us here: the still-ongoing ‘nature vs. nurture’ debate which, as we will see, has allowed anthropologists to ignore psychoactive plant use as a mere curiosity, or worse, as a perversion or degeneration of a supposed original ‘drug-free’ shamanism.
Anthropological paradigms of the 20th Century have vacillated between ‘nature and nurture’ as the prime cause of human behavior: whether it is culture or genetic inheritance that influences behavior the most strongly. In some professional circles the proponents of ‘cultural relativism’ had slowly gained ground to the point of flatly denying that anything like a universal ‘human nature’ need be considered important for theories of human behavior. It was an attempt to relegate notions of human nature to the realm of ‘folk psychology’, an attempt not alone among many other 20th Century efforts to ‘clear the decks’ and make of science something more precise and absolute, uncontaminated with certain perceived characteristics of 19th Century science.
And then there arrived on the scene a revolutionary little book entitled Human Universals. Its author, the anthropologist Donald E. Brown, argues that not only do universals exist, but “are important to any broad conception of the task of anthropology.” Brown immediately takes the offensive to explain how anthropology had taken a wrong turn:
…the study of universals has been effectively tabooed as an unintended consequence of assumptions that have predominated in anthropology (and other social sciences) throughout much of this century. From 1915 to 1934 American anthropologists established three fundamental principles about the nature of culture: that culture is a distinct kind of phenomenon that cannot be reduced to others (in particular, not to biology or psychology), that culture (rather than our physical nature) is the fundamental determinant of human behavior, and that culture is largely arbitrary. This combination of assumptions made universals anomalous and very likely to be rare; to admit or dwell upon their existence raised troubling questions about anthropology's fundamental assumptions. These assumptions also led many anthropologists to conclude or argue that anthropology should be narrowed from the study of humanity to the study of culture. [2]
While the final definition of a human universal may still be in a state of flux, Brown provides us with sufficient guidelines in his book so that we may apply the concept to our present endeavor. An important point is that although a human universal may have its roots in human biology, it is above all social and cultural in nature, and not merely trivial and physiological as some had claimed. Brown’s published list of universals is a thought-provoking list indeed, and includes a wide range of human behavioral characteristics. Some seem to be inherent in human nature and biology, while others are “cultural conventions that have come to have universal distribution.” Of particular interest for us here is this one: “Mood- or consciousness-altering techniques and/or substances.” Here, I shall claim that this is one of the most important, perhaps the most important and the very first of all human universals.
I should like to alter the definition of the universal a bit, however, to designate what must be its fundamental: it must be that the seeking of altered states of consciousness (ASCs) is the universal, and methods to do so subsidiary to the seeking. The methods themselves may or may not be quite so universal, since they can be quite varied in time and place. Certain societies have — and others we don’t know about may have — forgone or proscribed the use of psychoactive substances for various reasons, and/or enforced alternatives for substance use. Nevertheless, the use of psychoactives must remain at least a near-universal, since it is such a supremely effective way to alter consciousness. And psychoactive use must approach complete universality in the most ancient of societies where cultural organization was still in its early stages: in such early tribes and societies well-organized and often powerful priesthoods, the most likely source of psychoactive proscription or the imposition of substitute and even bogus methods for consciousness alteration, did not yet exist. Rudimentary shamanism was the norm for early man, and given the near-universal prevalence of psychoactive use in the shamanic tradition even today, it would be difficult to maintain that this does not reflect a universal practice for early man.
Donald Brown’s establishment of the importance of human universals for anthropology logically extends into the realm of paleo-anthropology, and supports the idea that psychoactive plant use must go back to the very beginnings of human existence. The question naturally arises, then, whether — or more importantly how — the use of psychoactive plants might have played a role in the sudden appearance of modern man some time between 50Ka and 150Ka (thousand years ago). There really are only three hypotheses to consider: psychoactive use 1) played no role whatsoever, 2) accompanied and perhaps assisted human emergence, and 3) was necessary for the evolution of humankind. The first hypothesis seems highly unlikely given the available evidence, and will probably only be adopted by those harboring a prejudicial anti-drug bias. It need not be considered here.
There exists an important precedent for thinking that the seeking of ASC’s is a human universal, and that is the intentional psychoactive drug use of a wide range of animals. Georgio Samorini, in his book Animals and Psychedelics, presents evidence that,
“…entirely on their own and without the influence of captivity or conditioning — wild animals, birds, and even insects do indeed drug themselves. This deliberate seeking of inebriation among all classes of animals is a perfectly natural, normative behaviour. Indeed, the pursuit of inebriation has been proposed as a kind of fourth drive — akin to hunger, thirst, and sex, so ubiquitous is its manifestation.” [3]
The evidence shows that although animals intoxicating themselves is a feature prevalent, but scattered throughout all levels of the animal world, it is not a universal in any given species or group of species. Yet it is common enough to conclude that it must be evidential of a general instinctive characteristic that humankind’s predecessors would very probably have shared with the rest of the animal kingdom. The seeking of ASCs becomes a universal, however, only with the advent of human existence. This was probably due to the co-existence of complex language as a means to make psychoactive use more than just an instinctive desire, occasionally realized, but to bring it into the cultural norms of the first manifestations of shamanism.
My reasons for making the second of these claims above, that the seeking of ASC’s was the very first human universal will become clear during the remainder of this chapter. I will argue that not only does the universal and the accompanying necessary psychoactive substance use pervade the earliest of human tribes, but that it was the first human universal, since without this catalyst proto-human social groups would have remained in that pre-human stasis that had already existed in East Africa for 100,000 years or more. During this long gestation, our not-yet-human predecessors were physically mature yet psychologically yet-to-be-born. Proto-man had exactly the same physical and neurological equipment we have today, yet his transition to early man did not take place. Then suddenly, one summer… or perhaps it was winter as I shall explain.
What Makyth a Man?
It has long been the accepted wisdom among many scientists, as well as the common mythology of public perception, that the rise of tool-making — technology — was an important, if not defining characteristic of the evolutionary process connecting advanced apes to Early Man. Specifically, it has long been hypothesized that Darwinian selection for increasingly intelligent hominids came about through selection for the best abilities to make and use tools. In the extreme, at least before recent studies of tool use and especially tool-making in some animal species, the technology of tools was thought to be a primary defining characteristic separating Homo sapiens from the animal kingdom. Also among extremities of interpretation has been the idea that tool-making and early technology might even have been the force driving the extraordinarily rapid increase in the size of the primate brain, from the first hominids of two or three million years ago with a brain volume of about 400 cubic centimeters, to modern man with a brain volume more than three times this figure.
It is understandably important to science to explain this evolution in brain size, for it has often been noted that, on an evolutionary time-scale, the rapidity of the change was practically unprecedented. Since the middle Pleistocene, about a half-million years ago, the rate of increase was particularly rapid, so much so that it has even been suggested that the enlargement might actually have been somewhat pathological, leading to a being whose irrationality and capability for wanton destructiveness equals or excels his creativity. Certainly, recent history has featured a wealth of both capabilities, but blaming our present situation on purported faults of evolution is neither productive nor scientifically logical.
It now appears that the tool-making hypotheses also have resulted less from a careful analysis of the data than from superficial concurrence of two tendencies. Recent work now shows it extremely likely that the ability to produce technology, it has been called object-intelligence for want of a better term, has been a development that has ‘piggy-backed’ upon a much more important development in intelligence, that which is required for social transaction. A recent collection of the important papers providing the foundation for the theory of Machiavellian Intelligence has been published as a book, [4] and one quotation should suffice to illustrate that even anthropologists such as Thomas Wynn, who might be surmised to have a vested interest in the importance of tool-use and making in the development of early hominids, has whole-heartedly agreed with the new view:
Given the evidence of brain evolution and the archaeological evidence of technological evolution, I think it fair to eliminate from consideration the simple scenario in which ability to make better and better tools selected for human intelligence. At almost no point in hominid evolution was there even a provocative correlation. The earliest known hominids, Australopithecus afarensis, had a brain larger than an ape's of equivalent size, but as far as we know, no greater reliance on tools. Early Homo at 2 Ma [million years ago] had a much more 'encephalized' brain, but the tools and even the context of use were not beyond the capacity of modern apes. Homo erectus did possess technology that was outside the range of ape behaviour, but by this time, 1.5 Ma, much of the encephalization of the Homo line had already occurred. In sum, most of the evolution of the human brain, the presumed anatomy of intelligence, had occurred prior to any evidence for technological sophistication and, as a consequence, it appears unlikely that technology itself played a central role in the evolution of this impressive human ability. [5]
As one of the contributors to the book remarked, Wynn’s paper “is a bombshell to the older ‘Tools makyth Man’ view... Wynn throws the question of the cause of human brain size back into the realm of the invisible: either the social relationships or the lifestyle which produced technology, not the technology itself.”[6]
The conclusions of the Machiavellian Intelligence hypothesis provide a key to the most probable evolutionary scenario for the influence of psychoactive plants in the emergence of modern humans. The arguments of the hypothesis show that the complexity of cognitive operations required for social interaction in large groups of individuals is far greater than that required for tool use or making, or for that matter any other activity of primate species.[7] Studies of societies of monkeys and apes in both natural and controlled environments strongly support the theoretical arguments. The brain size of various species of modern primates, for example, has been closely correlated with the size and complexity of the social groups of the various species studied. The complexity of social interaction would increase geometrically with the number of possible interrelations between animals in a group consisting of three or more generations of relatively long-lived animals. Dominance relationships, alliances, group undertakings such as efficient foraging and hunting, lengthy childhood, and relatively constant possibility of mating activity add to the complexity. The demands of increasing social complexity was a development requiring far faster biological evolution of the equipment which facilitated it than any previous set of demands such as tool use and manufacture, climate change, interactions with other species, or other hypothesized evolutionary pressures. Thus it is reasonable that the rapid increase in brain size among primates requires no other explanation, despite its unprecedented speed. The social transaction conclusions of the Machiavellian Intelligence hypothesis show how an advanced ape evolved to the point of having the required physical equipment to become artists, philosophers, musicians, and scientists, but as we shall see, proto-man, even with all this physical equipment, remained in a pre-human stasis for an extremely long period, changing little if any during the entire time. A further influence, sudden and catalytic, was necessary.
Evolutionary Scenario
Giving credit where it is certainly due, it is necessary here to mention that Terence McKenna has also presented a hypothesis parallel with mine concerning the necessary contribution of psychoactive use to human emergence. [8] We had discussed the idea in an exchange of letters before publication of his book, but it seemed to me even then that his proposed scenario put the critical influence of psychoactives in a far-too-distant time frame. In addition, his proposals that psychedelics were “mutation-causing” agents that “directly influenced the rapid reorganization of the brain’s information-processing capacities” seemed to me unsupported by any significant lines of evidence. The Machiavellian Intelligence hypothesis had not yet been published, however, nor had the genetic research that showed the ancestry of the entire human race to be very recent, and it was these two developments which provided me with a time-frame and psychological mechanism to support my own ‘psychedelic awakening’ scenario.
It remains now to show at what period an intervention of psychedelic influence is most likely in consideration of several areas of knowledge about fossils, human genetics, climate changes and catastrophic events, and other sources of information. The necessity for a ‘psychedelic intervention’ has been discussed elsewhere,[9] and will be summarised below.
Before presenting a possible evolutionary scenario however, let me explore further the idea of social complexity and its relation to the habit routine model of normal cognitive operation I have proposed. [10] I state that the power of the habit routine cognitive system would have increased with the increasing complexity of animal species, and would have reached its summit in proto-man. In our proto-ancestors we have a being whose potential intellectual capability extends to inventing mathematics and hypothesizing philosophy, yet for at least 100,000 years, with the identical equipment we possess today, we did no such thing. Our mental powers for original, creative, analytical thinking which are a natural product of that same intelligence that evolved for social transaction, were held in check by powerful evolutionary forces — except perhaps for use in extreme emergencies after which we would immediately revert to our habit-routine governed existence. The very requirements that brought our high-powered brain into existence — those necessary for complex social interaction — needed to be radically channeled to exclusive, habit-routine governed social use in normal times so that social coherence would be maintained, so that individuals in a social group used their powers in the established interests of the group, and so that group selection would further advance the evolution of advanced hominids. According to authors Elliot Sober and David Sloan Wilson, this was the essential situation for the evolution of unselfish or altruistic behavior. [11]
The Machiavellian Intelligence hypothesis and its proposed increasing social complexity fits perfectly with my surmise. Increased social complexity and the evolution of a large, expensive to support nervous system go hand in hand with extreme reliance on habit routine generation as the primary cognitive mechanism controlling behavior. One major consideration is that a large brain requires an excellent and copious diet, a requirement that would be fulfilled best in a social group able to cooperate on the highest levels to procure and share a wide variety of nutritious foods. An ability to avoid toxic plants as well would depend on complex social relationships as I will show in a moment.
It might be said that all these requirements would be an argument against the use of psychedelic agents in such social groups, an argument with which I entirely agree! The increasing social complexity and food requirements are arguments for the increasing power of ingrained and necessary habit routines that would prevent any cognitive breakthrough to using the new brain for purposes other than the maintenance of social order and group prosperity. Experimentation with new foods, such as psychedelic plants, would not in normal circumstances have been a common, or even likely occurrence. Any individual who developed a taste for consciousness alteration using psychoactive plants would likely be seen as disruptive and deviant, and be shunned or expelled from the social group. Such was the substance of Andrew Weil’s dismissal of McKenna’s “wild speculation” in Food of the Gods, expressed at the first Tucson conference on consciousness. [12]
Two quotations concerning the diet and food sources for primates will illustrate the point, the first quotation concerning the necessity for a rich and complex diet, the second on the ways this is fulfilled while yet preventing exposure to toxic (or presumably psychedelic) items:
Monkeys and apes have to balance their diet, which they do by wide ranging and yet selective eating; this is nicely illustrated by a study of Sri Lankan monkeys, Macaca sinica, by Marcel Hladik. By careful observation and quantification of their feeding, and phytochemical analysis of their food plants, he was able to show that for these 'frugivorous' monkeys, fruit was always more abundant than they could ever need. However, the monkeys had large day ranges and occupied a home range too large for efficient defense as a territory. Why? Their ranging was apparently a consequence of a need to eat fungi, rotten wood, insects, bark, shoots—a whole range of items that allowed them to make up the protein, vitamin, and mineral deficiencies of the energy-rich ripe fruit (Hladik 1975). The need for a balanced diet forces many primates to eat items that are hard to find. In studying baboon ecology, I was continually amazed at the subtle cues that they must use to identify some of their plant foods; at the most harsh time of year, the main survival foods were all either underground, or tiny and inconspicuous. [13]
Mother primates of several species pull their infants away from novel objects (two species of macaque), or remove foods from infants if the food is not part of the diet (chimpanzee). Caro and Hauser suggest that the latter might be 'accidental', but having seen it happen in gorillas, I doubt this (Anne Russon, who has noted the same in orang-utans, shares my scepticism). An infant gorilla was fiddling with and chewing at a leaf (of a species not normally eaten), facing away from the mother who was eating herself, when the mother broke off her feeding, reached over the infant's head and took the leaf, dropping it well out of the infant's reach. In the case of a chimpanzee watched by Mariko Hiraiwa-Hasegawa (1986), the mother not only did the same, but systematically picked every other leaf of the same species in the infant's reach and placed her foot firmly on the pile of leaves! But in any of these cases, the function is unclear: does the behaviour serve to teach, or simply to remove infants from danger? [14]
It has been proposed that the dietary requirements of animals with complex nervous systems was itself a factor in the evolution of hominid intelligence, the increasing need for a high-quality diet selecting for advances in intelligence and larger brains, which itself would demand further dietary improvements. [15] This must certainly be the case, but I think that the methods used by advancing species to procure better and better diets are themselves aspects of social behavior, and thus fall under the hypotheses of Machiavellian Intelligence. It was only through the advancing complexity of social life that the dietary requirements could be met, either for the actual procurement and sharing of foodstuffs or for the transmission of the knowledge of how to obtain them, and how to avoid serious errors such as ingesting toxic items.
Psychedelic influence on H. erectus and even more remote human predecessors is of course possible, as McKenna’s model suggests, but I believe it was unlikely, and if so, unimportant to either social or neurological evolution. Certainly, evidence is very sparse indeed, and there are important counter-arguments to be considered: For example, H. erectus lived on 3 continents in various habitats and through several periods of disruptive climatic change for a period of 1 or 2 million years, yet remained in a relatively unchanging state, with few signs of significant cultural or technological innovation. This is certainly a sign of normal, slow evolution, not psychedelically-assisted evolution. By contrast, the culture of early Greece, with psychedelic influence,[16] advanced dramatically from a quite primitive state to an advanced civilization in the space of a thousand years or so. In addition, the progression from Australopithecus to erectus to sapiens involved many different anatomical developments, not only brain size and reorganizations, but speech-enabling changes to the larynx, [17] even an enlargement of nerve canals in the spine suggested as facilitating the precise diaphragm control needed for speech, [18] and many other anatomical changes. This is certainly an argument for slow gradual evolution, not psychedelically-enabled or “psychedelic-mutagenic” evolution as suggested by McKenna.
From the preceding arguments concerning social stability, we may thus surmise that the influence of psychedelics on our immediate ancestors must have also involved some other simultaneous and important changes or events which helped to suppress the described tendencies to greater and greater dependence on habit routine as the primary determinant of normal behaviour. Some unusual change must have occurred to allow and ensure that psychedelic use would occur on a significant scale and would rapidly and irreversibly transform the habits of the hominid group that became the first group of modern humans.
It is necessary to point out, however, that the very brain changes which facilitated social evolution and a powerful habit routine cognitive system would be the same changes that would make an eventual psychedelic intervention most effective: A greatly expanded cortex to allow retention and access to long-lasting and complex memory data used for habit routine search and selection, would also be critical to eventually implement creativity and original thinking that was far more than random trial and error, creativity that could intentionally produce wide-ranging positive results. We would not expect attempts at individual creativity by a small-brained animal to result in much more than increased risk for that animal. A greatly expanded portion of the cortex involved with ‘association processing’ allowing the assembly of habit routines of a multisensory and intentional complexity, would also facilitate highly effective creativity. And a greatly expanded frontal cortex, the seat of working memory and other advanced cognitive abilities, facilitating habit routine based upon simultaneous nested levels of intentionality, would likewise be instrumental to a being requiring the frequent use of improvisation in situations which involved simultaneous trains of logical operations. The same nervous system improvements that enable advanced habit routine generation and use also provide for psychedelically-enlightened operation that is productive and creative, and not just hazardous to an animal. Here we have an additional argument against the influence of psychedelic agents at an early, small-brained stage of hominid evolution: psychedelics would not have ‘worked’ on hominids with limited brain capabilities.
One further argument will suffice to eliminate from consideration an early psychedelic influence on hominid evolution. The role of language in hominid development has been another hotly-debated topic. It is my contention that the psychedelic state of consciousness would have been of little or no creative value for an individual, and would have provided no evolutionary breakthrough for a social group which did not already have the benefit of complex language abilities. (I mentioned this above, as a reason why consciousness-alteration only became a universal with the advent of human social existence.) Psychedelic use and its effects are most valuable as a cumulative and social phenomenon. The psychedelic experience must not only be individually integrated but socially integrated as well, if it is to provide a key to rapid cultural advance as happened, for example, in ancient Greece. [16] There must arise a ‘psychedelic culture’ which is transmitted and developed from one generation to the next, and through which shamanism can arise. Without symbolic language, it is difficult to see how such a process might happen. Once a fairly complex language ability had evolved, however, we may imagine that psychedelic experience would have provided an impetus for further important language development into abilities concerned with the expression of the abstract, the mythical, the artistic… language capable of elaborating and transmitting tradition, a hallmark of culture.
Whereas written language is a cultural phenomenon which must be taught, (a child who is not taught to read and write will certainly not pick up the ability spontaneously), spoken language is assimilated spontaneously. Spoken language is a biologically-inherent feature of the human brain, a realization that became apparent to the linguist Noam Chomsky several decades ago. Steven Pinker, a former student of Chomsky, has made several conclusions concerning language and its evolution which are pertinent to a hypothesis of the time period in which psychedelic influence might have played a role in human evolution. [19] On the strength of much recent research, Pinker concludes that the first anatomically modern humans already spoke the equivalent of modern human language. Since language is intrinsic to the brain structures which produce and interpret it, language must have co-evolved with those structures, and have been fully realized with the advent of the brain with which it co-evolved. Spoken language was therefore not ‘invented’ at a late stage of that evolution, (although reading and writing most certainly were). Since language is inherently a social phenomenon, this proposed co-evolution of brain and language fits nicely with the Machiavellian Intelligence hypothesis of brain advances being driven by social requirements, including the advancement of language capability.
Pinker notes therefore that “language did not first appear in the Upper Paleolithic beginning about 30,000 years ago, contrary to claims frequently seen in archaeological...and popular science treatments.” [20] The idea that psychedelics would not have ‘worked’ on our small-brained forbears such as Australopithecus is supported by the proposed necessity of the existence of complex language as a precursor for the beneficial influence of psychedelics, and considerably narrows the time frame in which such influence must have played its role. Using conclusions from linguistics and brain evolution, we see that such a time frame should extend from about 150Ka to 50Ka (thousand years ago). I shall further narrow this window of opportunity for psychedelic influence in my arguments to follow. The important conclusion which has just been developed is that psychoactive plants in the environment cannot have played any significant role in either the early development of language, nor in the parallel development and tripling in size of the hominid brain during the period from about 3Ma to the appearance of anatomically modern humans about 150Ka.
Genetics to the Rescue
The suggestion of an evolutionary scenario for human development attempts to establish an actual series of events in history, if pre-history. Considering the very fragmentary evidence in the fossil record, and the indirect nature of other modern evidence to be described below, the chance for error in proposing the story of how Early Man made his way out of Eden is humbling. As we have seen above, the first theory of psychedelic evolution, that of McKenna, has suffered terminally from a dose of counter-argument all too easily supplied by the critics.
Much of McKenna’s book remains admirable however, for instance his presentation of evidence indicating the probable importance of psychedelic plants for the very early tribal societies which lived on the Tassili Plateau of southern Algeria, or Çatal Hüyük in central Anatolia. These are examples, along with ancient Greece and the Eleusinian Mysteries, which illustrate the rapid flowering of culture possible in societies in which there is strong, if not incontrovertible evidence of psychedelic use. The importance of psychedelics for early man certainly suggests an important evolutionary influence as well. The trick is to deduce, using a wide variety of ancient and modern evidence, when and where, and why that evolutionary influence might have taken place. Let me start by considering some modern reinterpretations of the fossil evidence which have recently received overwhelming support from one of science’s most recent and fascinating developments, molecular genetics.
Chris Stringer, who is today the head of the Human Origins Group of the Natural History Museum in London, recounts a most interesting tale of scientific discovery in his recent book, African Exodus, co-authored by the science writer Robin McKie. It is the kind of story which has epitomized the romance and excitement of scientific discovery and revolution as perceived by the lay public, stories such as the Curies’ discovery of radium or Galileo’s road to revolutionary views of the heavens. But not only is the story of these recent discoveries concerning human origins of interest to the general public, it represents a Kuhnian scientific revolution [21] of important scope, comparable to the recent revolution in geology with the advent of the discovery of plate tectonics, or even the revolution in physics earlier in the 20th century.
The first chapters of African Exodus are concerned with a close examination of the archaeological ‘bones and stones’, in which Dr. Stringer shows how the Multiregional Hypothesis [22] of human evolution, the predominant model for most of the last century, has just recently been discredited in favor of an Out-of-Africa (actually an Out-of-Africa II) [23] model. A new mathematical technique, multivariate analysis, used by Dr. Stringer during his several years of work on the fossils, led him to doubt the validity of the multiregional theory early on in his career. But only a small minority of paleoanthropologists were ready to listen to new analyses of fossil characteristics which called into question the status quo of their profession, for many great scientists of the past decades had analyzed these same fossils and there was wide consensus that a multiregional scenario was the correct one. The upheavals and conflicts typical of a newly-born scientific revolution ensued. A revolutionary new idea proposed by a small group of scientists, at first rejected as absurd by the establishment, soon began to topple that establishment. Chris Stringer and Robin McKie introduce the book:
For the past few years, a small group of scientists has been accumulating evidence that has revolutionised our awareness of ourselves, and our animal origins. They have shown that we belong to a young species, which rose like a phoenix from a crisis which threatened its very survival, and then conquered the world in a few millennia. The story is an intriguing and mysterious one, and it challenges many basic assumptions we have about ourselves... It is a remarkable, and highly controversial narrative that has generated headlines round the world and which has been the subject of a sustained programme of vilification by scientists who have spent their lives committed to the opposing view that we have an ancient, million-year-old ancestry. The debate, which reverberates in museums, universities and learned institutions across the world, is one of the most bitter in the history of science. [24]
What finally broke the dam of resistance to the new ideas was the entry upon the scene of revolutionary new techniques from a field which had previously played no role whatever in paleoanthropology, molecular genetics. Until very recently, the possibility that we might learn something about the evolution of our distant ancestors by studying the genetic makeup of living humans was hardly even suspected, and of course the techniques for doing so completely unknown. But all this changed rapidly as the science of molecular genetics grew from its infancy in the 1960’s to the powerful tool it is today. The use of genetic analysis for understanding evolution, the science of molecular anthropology, also had its beginning the 1960’s, with the pioneering work of Allan Wilson (later to be a key player in the confirmation of the Out-of-Africa scenario) and Vincent Sarich. It was their early work that began to topple many sacred cows of paleoanthropology, the first to fall being the idea that apes and humans had diverged very early, between fifteen and thirty Ma. By comparing protein structures of modern apes and man, Wilson and Sarich concluded that the separation could have been no earlier than 5Ma. “We were variously ignored, abused and scorned,” recalls Sarich. But it was the first of many venerable precepts of paleoanthropology that was to fall to the new techniques of genetic analysis. The research of Wilson and the many others who followed came along at precisely the right time to resoundingly confirm the early work of Stringer.
Stringer and McKie mention in their introduction above that our species “rose like a phoenix from a crisis which threatened its very survival,” and propose later on in the book the occurrence of a population bottleneck sometime about 100 to 150Ka. The possibility of such a bottleneck has also drawn criticism from defenders of the orthodoxy, yet again the genetic evidence is what has come to the forefront to support the proposal.
The genetic evidence in question was not at first concerned with the DNA of the cell nuclei, found in every cell of the body and which is responsible for control of the growing embryo and inheritance of physical traits, but DNA contained the mitochondria of these same cells. These small structures within animal cells act like metabolic power-packs, enabling the biochemical reactions which provide the cell with energy. That these structures contain their own DNA, entirely different from nuclear DNA, is something of a curiosity, and has led to speculation that very early on in evolution, mitochondria might have been a separate organism which developed a symbiotic relationship with primitive single-celled life forms to enable the evolution of the first true single-celled animals. Whatever their evolutionary story, the mitochondria and their independently organized DNA strands have provided an important key for the understanding of hominid evolution. Two specific characteristics of mtDNA (mitochondrial DNA) figure importantly: firstly, mtDNA is transmitted only through the female lineage, since the mitochondria of sperm reside in the cell’s extra-nuclear protoplasm, and do not enter the egg at fertilization. Thus mtDNA provides a powerful tool for tracing genealogies in animals, and reconstructing recent evolutionary trees. Secondly, mtDNA has a relatively high and constant rate of random mutation which is conveniently analyzed, thus constituting a ‘molecular clock’ providing genetic markers for accurately tracing migration and fissioning in human societies. A recent paper by Rebecca L. Cann, an early associate of Allan C. Wilson, explains more fully the peculiarities of mtDNA which result in its being such a powerful tool for the study of evolution. Concerning the bottleneck hypothesis resulting from mtDNA studies she recounts:
When I began my study of mtDNA in the late 1970s with Dr. Allan C. Wilson, one of his postdoctoral fellows, Dr. Wesley Brown, was writing up his work on a study of 21 human mtDNAs. Dr. Brown had discovered that using restriction fragment length polymorphisms (RFLPs), humans as a species looked 'different' to other mammals. He found that in comparison to two chimpanzees, or two gorillas, or two orang-utans, or two gibbons, or even two pocket gophers, humans had only one-half to one-fifth of the intraspecific variability seen in our closest primate relatives and other genetically well-characterized mammals. In 1980, Brown proposed that the level of variability sampled in his study was consistent with the derivation of the human mitochondrial sequence from a single female about 200,000 years ago. This was the origin of the bottle-neck hypothesis and mitochondrial 'Eve'. [25]
The mitochondrial “Eve” hypothesis naturally made big headlines, was featured on the cover of such magazines as Time and Newsweek, and also quite naturally was journalistically exaggerated out of all proportion to the original claims. A concerted attack by the multiregionalist ‘old guard’ also helped to make the new idea sound a bit absurd, both to the public, and to scientists in other fields not yet acquainted with the genetic evidence. All the criticisms have been adequately countered however, and the findings confirmed by newer and more complete studies, including studies on the nuclear DNA. Rebecca Cann was careful to explain, in the above quoted paper, the intended interpretation of the hypothesis concerning the possible number of individuals existing at the time of the proposed bottleneck. Since mtDNA is passed on only through the female lineage, the existence of a mitochondrial ‘Eve’ does not imply that our nuclear DNA is also descended from a single individual, nor that at one point the human lineage was reduced to a single, or mere handful of individuals (the ‘Biblical Eve’ scenario!) Recent estimates of the number of individuals existing at the time of the bottleneck, including that of Chris Stringer, puts the number at perhaps ten thousand. [26] It may be argued that a population of ten thousand individuals is not what one could call a genetic bottleneck, yet the sum of the genetic evidence indicates that “there were at least 100,000 adult archaic forebears of our Africa ancestors about 200,000 years ago.” [27] Thus a decrease to 10,000 individuals is certainly a ‘population crash’ indicative of important events in the early evolution of modern man.
As for the date of the lifetime of ‘mitochondrial Eve,’ there have been various estimates between the extremes of about 60 to 400Ka based on several different methods of mtDNA analysis. Some best estimates put the life of mitochondrial Eve at about 130 to 140Ka, “the date of origin of modern humans.” [28] The uncertainties in these several estimates may be narrowed by considering data from other fields of study, and from a view of the overall evolutionary scenario which emerges upon consideration of all the information at our disposal, including my own hypotheses of the influence of psychedelics on the overall process. Using all these sources, a reasonably constrained sequence of events with fairly accurate dates becomes possible.
[…to be continued]
Loving this lesson, so far...