| ||Who knoweth the spirit of man that goeth upward, and the spirit of the beast that goeth downward to the earth?|
| ||Ecclesiastes, 3, 21 [King James Authorised Version]|
A person can remain indifferent to many things but not to his own personality. In himself he finds everything to be extremely interesting: appearance, mentality, intellectual abilities and especially origin. Features of parents are usually carefully searched for and cherished. All nations have an idea of the nobility of ancestors, or to put it another way there is an ancestor cult. It is regrettable that this worship is sometimes transformed into nationalism, when representatives of different nations are ready to do their utmost to establish the superiority of their forefathers and consequently their own exclusiveness.
Curiously, it is the natural tendency to self-praise which makes us isolate our species from the rest of the animal world and set ourselves on a pedestal. The very name of the species, Homo sapiens - that is, "man intellectual" - sounds very grand in itself. Impressed by our species' peculiarities we are often enough ready to deny our relationship to other animals and to trace our origin to some divinity or, following a fashion, to strangers from extraterrestrial worlds.
An evident similarity with animals often hurts our dignity. For example, in the book "The Descent of Man and Selection in Relation to Sex" by Charles Darwin (1809-1882) one can find an explanation why some African tribes knock out their canines and paint their teeth blue (Darwin, 1871). It appears that they do not want to look like dogs. However, under the pressure of incontrovertible evidence and having agreed - although painfully - to admit our relationship with other animals, and that we belong to the same group with monkeys, we gave it a rather presumptuous name - "primates", that is, "the first". It is as if the name itself provided "scientific" evidence of the relationship of human beings to the most perfect animals. Our closest relatives are apes - anthropoids. For example, man and the chimpanzee share not less than 99% of their genes (King, Wilson, 1975). We have no one organ, no one structure (even the appendix) which the anthropoids do not also have. Such a striking similarity makes us place the apes above other animals and call them higher primates.
Let us try to view the higher primates objectively and forget for a while our close relationship with them. We know that nowadays on the Earth there live only a few species of these apes with a rather cryptic mode of life in the tropical forests of Africa and Asia (Foley, 1987). Their populations are quite small and species such as the orangutan and gorilla are dangerously close to extinction. Although apes' mode of life and behaviour share many common features with those of man, nonetheless they probably do not possess the main justification for our state of dignity - abstract thought. In any case, even if they possess it, they evidently do not use it. So we cannot argue, just by acknowledging their similarity to ourselves, why for example the gorilla should be considered more perfect than the leopard or the ox, or even any beetle.
In speaking about the greatness of our animal ancestors we should not forget about other representatives of our genus Homo (Foley, 1987). Where are they? Paleontologists say that this genus never was endowed with an abundance of species, but in bygone times there existed Homo habilis ("man efficient") and various representatives of Homo erectus ("man upright-walking"). Only quite recently (about 50 thousand years ago) there existed a closely related species, or even subspecies - Neanderthal Man (Homo sapiens neanderthalensis). By the way, as to the size of his brain, he was not inferior to us, and some characteristics of his burials give clear evidence of his ability to think abstractly. Nevertheless Neanderthal Man became extinct, probably through being unable to survive the struggle for existence. Of course the direct causes of this event are a matter for speculation: perhaps it was our own species (or subspecies) which made Neanderthals die out, or perhaps they just melted away by hybridising with other races.
Finally, remember the very recent past. What was H.sapiens some 15 thousand years ago? Small nomadic groups (20-30 persons) of hunter-gatherers lost in vast areas of virgin forest do not suggest audacious conquerors of Nature. Look attentively at the aborigines of Australia or the Indians of Amazonia, listen to their myths and legends, and you would be impressed by the respect and even awe inherent to their relationships not only with large mammals - the main objects of their hunting - but also with quite small animals, birds and reptiles. Our own fairy tales and superstitions are abundantly supplied with mutual transformations of humans, animals and plants. In all these stories the human does not emerge as a proud giant but rather as a timid implorer begging demons for luck in such an unreliable business as hunting.
The situation changed radically with the development of farming and animal breeding. An ability to control the reproduction of several animal and plant species made it possible for humans to feel their superiority over them. The new attitude to Nature was reflected in the Old Testament where God says of the newly created people: "let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth" [Genesis 1,26; King James Authorised Version]. Thus, our everyday anthropocentrism is no more than 8-10 thousand years old.
The ongoing historical process was accompanied by continual technical progress - directed not at all to the benefit of mankind but based on much more prosaic, so called "prestige economics". Representatives of the human race in their majority aspired - and still aspire - not so much for satisfaction of their needs in food, shelter and so on as for a higher position on the social ladder. The main "objective" arguments for social status usually admitted by society are connection with the aristocracy and so called wealth. Our sporting, competitive spirit - quite appropriate in prehistoric times - now prevents us from getting rid of such shortcomings as pragmatism, nationalism and ... - anthropocentrism.
All contemporary educated people know, of course, that all of the surrounding organic world is the product of a natural process called "evolution". They also know that the theory of evolution was put forward by Charles Darwin. The theory states that every following generation is adapted for life slightly better than the preceding and in this respect is slightly more perfect. It means that in the course of evolution there should be a continuous advancement of all forms of life.
As we know from college, at some time in the Ordovician fish made their appearance on our planet (see the table), then in the Devonian-Carboniferous the amphibians, having branched from the fish, became pioneers on the land. Amphibians gave rise to reptiles, which during the Mesozoic era generated a vast diversity of life forms with dinosaurs the most prominent among them. Then the dinosaurs together with other monsters (pterodactyls, ichthyosaurs and others) became extinct by the end of the Cretaceous, so yielding the planet to the more progressive birds and mammals. The latter rapidly improved and gave rise to the higher primates. Finally, some 15 million years ago there appeared the first representatives of the family Hominidae. Evolution of the hominids advanced, as seen in an increase of the brain, in development and improvement of speech, and in tools. The stages quickly flashed by: Ramopithecus, Australopithecus, "efficient man", "upright-walking man" (Pithecanthropus, Sinanthropus, Heidelberg Man), Neanderthal Man and at last our species (or subspecies) - Cromagnon Man. Bravo! We are the champions! We are ahead of everyone else! Our undoubted perfection is well-deserved.
However, look around you. Today the Earth is inhabited by not less than 2 million animal species biologically equivalent to ourselves. Two million species turn out to have finished the same evolutionary race alongside us. Each species had its progenitor and is the glorious culmination of a long chain of precursors embracing at least 2 billion years. But if fishes are lower, that is, less perfect, why have they not become extinct? And how come that nowadays freshwater and seas harbour at least twenty thousand species of them? Why have not all the reptiles perished? Even after terrible catastrophes afflicted the Earth in the late Cretaceous, modern reptiles are as abundant as mammals. We can accept that the surviving reptiles are more perfect than the extinct, but in this case one should admit that snakes and lizards have a higher organizational level than did dinosaurs, ichthyosaurs and plesiosaurs. No zoologist should agree with such a view. The miserable species abundance of the higher primates has already been discussed. So in the end we have perfect nonsense! The majority of animal species is represented by invertebrates among which the first place is occupied by insects. Some families of beetles or butterflies contain more species than the entire Chordata with all the vertebrates (fig.1) (Ross et al., 1982).
Thus, viewed objectively, the winners in the competition for life are insects. The well-known sequence fish-amphibians-reptiles-birds-mammals-man is no more than a series of new forms. The fact that the land was occupied by amphibians and reptiles and not by fish is quite trivial. The new existing beside the old may turn out to be not a matter of improvement but merely of difference. Thus, we see that a straightforward approach connecting perfection with a victory in the struggle for life leads us to a paradox.
However, stop! Is it not evident that the organizational level of fish is lower than that of birds and mammals? Is it not evident that infusoria and amoebas are simpler than any worm, while lower plants like mosses are more primitive than palms and eucalyptuses? In fact, why should we ignore the opinion of pre-Darwinian sages who were alive when the magic phrases "natural selection" and "struggle for life" were not yet said?
The concept of differences in the perfection of organisms inhabiting the Earth is based, first of all, on our anthropocentrism. On the one hand we consider ourselves as part of the animal world, on the other hand clearly realize the "gulf" separating man from other animals. The crucial difference consists not in that we lack fur, walk on only two limbs and articulate sounds, but in that we are capable of abstract thought. This ability allows people to plan their affairs by subordinating them to clearly stated aims. However, the same ability makes us not only contemplate natural processes but also ask, "What are they for?" This question helps us to understand people's behaviour, but is it legitimate in other cases? For example, the question "What for does the sun shine?" will most probably bring a smile since the shining of the sun has no aim. However, even recently a reply to this question might be: "In order to give us light and heat". Even such a respected sage as Aristotle (384-322 B.C.) considered everything in Nature to exist for the sake of something or to correspond to a thing which exists for the sake of something.
Assuming humans' ability to pose specific aims to be the highest form of behaviour of living beings, Aristotle was the first to classify them by the degree of perfection. The lowest stage he allocated to plants with their vegetative soul, that is an ability for growing and reproduction. A little higher were placed "the lower" sluggish animals with a capacity for sensation only by direct contact (i.e. possessing tactile sense and taste). The following stage was occupied by mobile animals able to receive signals from a distance by means of sight, hearing, and sense of smell. Their aspirations were not based on reasoning, but they were able to imagine. On the highest step was placed the one and only animal - man - which possessed not only imagination but also reason.
An ascending ladder of beings was arranged by Aristotle according to the complication of their souls (for a modern English translation of his book 'De anima' see ref. Aristotle, 1956). Vegetative soul was inherent to all members of the sequence, "higher" animals displaying all the properties typical of the "lower" soul. Man had the most complex soul. This sounds logical enough, but the terms "lower" and "higher" cause some dissatisfaction. Even assuming the soul of the higher beings to consist of larger number of elements we cannot argue that "larger" necessarily means "higher".
It is possible that the reason for considering complication as equal to elevation lies in peculiarities of the social life. Note that those who give orders are assumed to be the higher and authorities are often called "upper strata". Every human even from the very bottom of the social ladder can command domestic animals and therefore he is higher than they are. Aristotle supposed that the higher position of humans over that of other mobile animals was associated with a higher complexity of the human soul, and so continued the descending series to lower animals and plants.
Aristotle did not explain how the ladder of organisms had come about. However, taking into account some characteristics of his philosophy one can suppose that motive forces were determined by so called ultimate goals - teleofactors. Under their influence matter permanently tended to acquire more complex and harmonic forms. The idea of Nature's aspiration to more complex organization became an inalienable element in the majority of philosophic theories of the following centuries.
An anthropocentric principle of classifying living organisms was retained for two millennia. Even the famous French biologist Jean-Baptiste Lamarck (1744-1829) stated that "One can admit as a reliable fact and evident truth that of all animal species it is human organization which is the most complex and perfect both as a whole and in respect of those capabilities which are imposed by it"; furthermore, "one can postulate that the closer the organization of an animal to that of man, the more complicated it is and the higher perfection it has achieved, and vice versa - the further this organization from the human, the simpler it is and less perfect" (Lamarck, 1809)
Lamarck's theory of evolution implies that the steps in the evolutionary ladder (gradation) were filled continually from the bottom to the top, and the process was governed by a specific "natural force". This mysterious force was hindered by some "altering force" which disturbed the strict correspondence to the principle of gradation. Note that Lamarck considered complication as being equal to perfection, therefore, he stated that living beings in the course of evolution changed from simpler to more complex and simultaneously from more primitive to more perfect. According to his theory the most primitive, simple organisms were derived from inert matter by self-origination.
Thus we see that Lamarck's theory is not very helpful in searching for an answer to how we classify organisms by the degree of their perfection. Similarity with man, even neglecting the artificiality of the comparison, can hardly help in estimating the degree of perfection of invertebrates: they all are equally remote from the human being. Interestingly, though not very logically, anthropocentrism is retained even among contemporary anthropologists. For example, Jan Jelinek (1985) in his "Large Illustrated Atlas of the Prehistoric Man" notes that "man, or to put it scientifically, Homo sapiens, is the most perfect of all living beings."
Strange as it may seem, a prominent contribution to the objective substantiation of the ladder of creatures was made by a formidable opponent of the evolutionary idea - the famous Georges Cuvier (1769-1832). He wished to base his classification on pure facts and tried to reveal the most typical feature for each kingdom of living beings. In his opinion just such a feature was the structure of the nervous system, which was "in fact the whole animal; other systems are only there to support and attend it." Accordingly, all animals were divided into four types - vertebrates, mollusks, segmented and radiate (Cuvier, 1817). We see that Cuvier virtually materialized the substance which was called "soul" by Aristotle. Having chosen this feature as best reflecting the nature of an animal organism, exactly following the great Greek, he found its essence in the development of psychics and moving activity.
With all due respect to Cuvier it is difficult to agree with his classification of organs as more and less important. It is well known that all organs are equally essential and necessary to support life. Damage to a brain as well as to the heart or kidneys or gut equally "reliably" leads to disease and then to death. As a matter of fact Cuvier considered "every organism to comprise an isolated unity" and "if any organ function be changed not in line with alterations of other functions of an organism, it will be unable to exist."
We must agree that the nervous system plays an essential role in providing integrity of an organism, however the circulatory system is hardly less significant, so we cannot decide which of them is more important for an animal. And what about the kidneys: are they more or less important? Thus it seems that the nervous system was chosen as an "objective" criterion for the sole reason that the brain is maximally developed in humans. Therefore, choosing as a criterion for organizational level either the soul's complexity or the type of nervous system is equally determined by anthropocentrism.
Darwin's idea of natural selection is based on the concept of different fitness of competing individuals, and survival of the more adapted does not necessarily imply the survival of the more complex or more progressive. In this connection it is not surprising that one of Darwin's closest adherents, Thomas Henry Huxley (1825-1895), was very sceptical about the idea of evolutionary progress. He was deeply impressed by so called "persistent" forms, that is, species and genera that have not changed for tens and even hundreds of millions of years (Huxley, 1862). These forms are not infrequent among molluscs, echinoderms and brachiopods. It is sufficient to mention a shrimp Triops, a phyllopode crustacean which has retained its generic (and maybe specific) constancy for more than 200 million years (Zhizn' Zhivotnykh, V. II, 1988).
Huxley supposed all recent organisms to be equally well adapted to their environments and considered subdivision into the higher and the lower as non-scientific. Darwin's own attitude to the problem is reflected in a fragment of his letter to Joseph D.Hooker dated 30th December 1858: "...I do not think that any one has a definite idea what is meant by higher, except in classes which can loosely be compared with man"(The Corespondence... , 1991). The majority of modern darwinists suppose division into "the higher" and "the lower" to be old-fashioned and treat the term "progressive" quite freely. For example, one of the founders of the Synthetic Theory of Evolution, George Gaylord Simpson (1953), considered a taxon to be more progressive merely if it had appeared later in evolution. Approximately the same meaning of the term "progressive" was implied by another well-known American evolutionist, Verne Grant (1985).
It is interesting that a grandson of T.H.Huxley, Julian Sorell Huxley, turned out to be a keen adherent of the idea of evolutionary progress and revived it among darwinists. Julian Huxley focussed the attention of evolutionists on the phenomenon of replacement of prevailing (dominant) forms (Huxley, 1942). From the paleontological record it is clear that in the Ordovician seas there predominated molluscs, trilobites and brachiopods; in the Devonian supremacy was won by fish; on land during the whole Mesozoic reptiles were dominant; the Tertiary period was the reign of birds and mammals; and finally, in the Quarternary period, authority over Nature came to man (see table).
Julian Huxley (1942) tried to find objective criteria of evolutionary progress. He supposed that these were : 1) increased rate of metabolism; 2) care of progeny; 3) accelerated response to environmental signals; 4) increased ability to control the environment and, in particular, less dependence on it. The last point seems however to be somewhat romantic, although Julian Huxley attributed it the utmost importance. The thesis of controlling the environment sounds especially odd, since it can be imagined only in regard to mankind. But even for us governing Nature is far from being real: today we merely "conquer" it.
The anthropocentrism of Julian Huxley emerges even more clearly in his idea of absolute progress leading to man. Quite traditionally most attention is paid to the development of the central nervous system as the principal mean of gaining independence from environments.
The idea of absolute progress was developed by the Soviet evolutionist Kirill Zavadskii (1958) in his concept of "arterial progress" leading to man. Thus, once more we face the point of view stated by Aristotle. It was expressed even more clearly by Pierre Teilhard de Chardin (1965), a French paleontologist and philosopher, one of the discoverers of a Sinanthropus, and a person who searched for a compromise between science and religion. He wrote: "...disregarding any anthropocentrism and anthropomorphism I suppose that there exists a direction (sens) and a line of progress of life so profound that their reality, as I am sure, will be generally acknowledged by future science."
He looked for the Ariadne's thread to escape from the labyrinth of heterogeneous evolutionary concepts. As expected, he found the guideline in the degree of development of the nervous system and psychics. Having performed this old trick Teilhard de Chardin exclaims: "As soon as we take for a measure (or parameter) of an evolutionary phenomenon the performance of the nervous system, not only do numerous genera and species arrange themselves in a series, but the whole network of their sprays, layers and branches rises as a quivering bouquet. The distribution of animal forms by the degree of development of their brain not only perfectly coincides with contours outlined by systematics, but lends to the tree of life a relief, a face, an impulse so that one can not help admitting the truth. Such a harmony, being so natural, steadily constant and eloquent, cannot be accidental."
Of course, we must admit that in the lineage leading from fish to man there did take place an increase in relative dimensions of the brain, especially of its front sections. However, we have no reason to emphasize this particular trend. In the fish-to-mammals lineage progressive enlargement and complication were also undergone by the heart and vascular system, the kidneys, lungs, and structures sustaining homeostasis. At the same time in the same lineage one can note a tendency for decreasing reproductive potential which is nonetheless compensated by transition to viviparity and increased care of progeny.
We have every reason to consider development of adaptations to an aquatic mode of life by ancestors of the pinnipeds and whales as being progressive. These adaptations include transformation of limbs, skin, teeth and so on. Especially impressive is the acquisition by whales of an echolocation system - absolutely novel for mammals - with powerful development of the relevant brain sections. This is true also with regard to progressive development of adaptation to an aerial mode of life by ancestors of the bats. Finally, why not consider the progressive development of the reproductive system in many flatworms which adopted parasitism?
As a rule, in discussing adaptations to a parasitic mode of life most attention is paid to the phenomenon of degradation (regress) of many structures necessary for a free-living organism. However, it is hard to speak seriously of degradation since the ancestral forms, in spite of their free way of life, were very simple minute wormlets swimming by means of bristles. It should be noted that the flourishing of mankind in a biological sense was until recently to a large extent hindered by these very parasites. Yet now in many regions of the globe the "crown of life" is afflicted by them virtually without exception. In fact, how can one fight such a helminth as the tapeworm? Its body consists of several thousand rather autonomous segments - proglottids. The central organ of each proglottid is a womb containing up to 175 thousand eggs and in every 24 hours a tapeworm living in a human produces about 5 million eggs (Zhizn' Zhivotnykh, V. I. 1987)!
Thus, if anthropocentrism is rejected we have no objective reason to emphasize progressive development of the central nervous system. We must consider it as a special case of a widespread phenomenon - enlargement and complication in the course of prolonged evolution of some organ or system of organs. We shall try to give a rational explanation for this evolutionary tendency.
The first theory explaining the ladder of living beings from an evolutionary point of view was put forward by Lamarck (1809). He formulated its main postulates in the following four laws:
"The first law. Life by its own power constantly tends to increase the volume of any body possessing life and extend the dimensions of parts of the body up to the limits determined by life itself.
The second law. Formation of a novel organ in the body of an animal is a result of a new requirement which continues to be felt, and of a new movement generated and supported by this requirement.
The third law. Development of organs and the power of their action always correspond to the use of these organs.
The fourth law. Everything which was acquired, impressed or altered in the organization of individuals in the course of their life is conserved in reproduction and transferred to new individuals having experienced these alterations."
The truth of these laws was for Lamarck self-evident. Let us turn to the first law. Do we not observe growth of an organism in the course of its development? Is it not evidence of the existence of a special "growth force"? The second and the third laws postulate facts well known to everybody concerning the increasing effectiveness of many organs in the course of their training. In fact, if needed, a man can develop his ability to run by intensive exercises and significantly improve his sporting achievements. In the course of training, his skeleton, muscles, respiratory and circulatory systems undergo adequate, that is, purposeful alterations. Why not suppose that by means of exercises the man sends his growth force to organs with inadequate performance? This means that distribution of the growth force in the organism is under psychical control. The fact that people (and animals even more so) are not always aware of their structural details is of no importance since the growth force (in the form of specific material particles - fluids) can be transmitted entirely unconsciously.
However, the fourth law, to put it mildly, is rather puzzling. Where had Lamarck observed its action? Perhaps his only source was the "folk wisdom" like that noted by Alexander Pushkin in his "Tale of the Dead Tsarevna and the Seven Bogatyrs"? In that tale the stepmother, indignant about whiteness of the face of her stepdaughter, exclaims:
Another example of the direct action of the visual sensation of a mother on the appearance of her progeny is given by the Bible. In order for unicolor sheep and goats to give birth to spotted offspring Jacob put withies into a watering trough, and cattle "having come to drink conceived in front of the withies". Then, optical sensations of the mothers from the tangle of osiers were transformed into spots on the skin of the lambs and kids.
The belief in inheritance of acquired characters in Lamarck's days seems to have been widespread. Even the cynic Diderot (1875) supposed that if the arms were cut from men for several generations at last there would be nothing left to cut. To refute this fallacy the originator of neodarwinism August Weismann (1834-1914) cut tails from mice for 22 generations, but observed no alteration in the descendants' tails (Weismann, 1893).
An additional reason for the fourth law rested on a contemporary concept of universal harmony in the world. In such a philosophy there was no place for any accident, therefore, it was impossible to imagine the spontaneous occurrence of novel expedient properties. In fact, if an organ's degree of development perfectly corresponds to the organism's requirements there should exist a special mechanism to provide such a correspondence in variable environments. Being restricted by his mechanical determinism Lamarck had to search for a solution to the problem in the form of a dynamic law which could connect environmental alterations with adequate and heritable changes in an organism.
In spite of their scientific-like form Lamarck's laws could not persuade clear-thinking people. Being unable to observe species alterating in time they continued strictly to adhere (as they supposed) to the facts and so kept their faith in divine creation. A prominent authority in the biology of that time, Cuvier - who was acquainted with Lamarck's main work, "Philosophy of Zoology" - claimed that "nobody considers this philosophy to be so dangerous that it is necessary to refute it." (cited according to: Lunkevich, 1960) The concept of species constancy did not appear to be challenged. Although the vast diversity of species had to come about somehow, the scientific philosophy of Cuvier allowed him to take into consideration only phenomena accessible to observation. Since cats, dogs, ibises and other animals mummified by ancient Egyptians several thousand years ago did not differ from contemporary forms, the problem of species formation could be considered inaccessible to experiment, that is non-scientific. By the way, a similar attitude to the problem of the origin of life on Earth is common among contemporary biologists. Different theories on this subject tend to be met with some scepticism, as if the subject is not to be taken very seriously.
As a matter of fact Darwin was the first to introduce to biology a concept of the random. As the main model of evolutionary change he chose the process of breeding economically beneficial plant and animal forms by man. Darwin put forward the idea that the main motive factor of this process was selection of individuals somewhat deviating from the average in the direction favoured by the selectionist. These slight "deviations" are often transferred to offspring, therefore prolonged selection accumulates the deviations, resulting finally in a considerable shift of properties of the average individual. In his main work "Origin of Species by Means of Natural Selection" (1859) he wrote: "If selection consisted merely in separating some very distinct variety, and breeding from it, the principle would be so obvious as hardly to be worth notice; but its importance consists in the great effect produced by the accumulation in one direction, during successive generations, of differences absolutely inappreciable by an uneducated eye - differences which I for one have vainly attempted to appreciate."
How can this subtle heritable variation occur? According to the original version of Darwin's theory it occurs spontaneously without any association with environmental conditions. However, Darwin did not present direct arguments for this very important postulate. Random mode of occurrence of heritable variation did cause him confusion. For this reason he attempted to assure his opponents that chance was no more than poorly understood regularity, and that the mode of hereditary variation was somehow affected by environments, exercises and so on. At the same time advances of deliberate as well as unconscious selection in breeding valuable plant and animal forms provided clear evidence that without any training, ignoring any conscious effort on the part of the selected individuals, enormous unidirectional shifts in their organization were possible. It was quite evident that a selectionist did not provide special conditions for the occurrence of hereditary variation: it appeared by itself.
Darwin had transferred the concept of spontaneously occurring heritable variation of every trait onto natural populations. Having chosen as a key trait the fitness of an individual - that is, the probability of leaving adult offspring - Darwin found a way of understanding the process of natural selection. A strange, rather dismal prospect opened before him: slightly differing individuals of the same species competed among themselves for the privilege of representing peculiarities of their structure in the following generation. Because of limited food resources the majority of descendants irreversibly perished in this competition.
While the very fact of evolution - that is, alteration of species through time - was adopted by contemporaries rather easily, the mechanisms gained acceptance much more painfully. Due to the works of Lamarck and the German nature philosophers, the idea of evolution was not unexpected. The idea of natural selection had also been widely accepted. Only the source of the heritable variation remained obscure. It should be noted that in the days of Darwin and later up to the early 20th century heredity was considered as some liquid (usually called "blood"). The hereditary properties of the two parents were thought to be mixed in the act of fertilization. Now let us imagine that an individual with a favourable heritable deviation mates with an ordinary average individual of the same species. In such a case, according to the "theory of blood", the favourable feature in the progeny will be diluted to half strength. Further mating with other average individuals will dilute the beneficial property fourfold, and so on. It is quite clear that, since favourable hereditary alterations are rare events, they would be inevitably diluted in subsequent generations and disappear. This argument was put forward by the engineer F.Jenkin, and Darwin was unable to give him a reasonable answer.
The only way to get rid of the "Jenkin's nightmare" was to increase sharply the rate of occurrence of similar favourable alterations. Another difficulty was connected with the indefinite direction of variation. According to Darwin's theory favourable alterations should always be accompanied by unfavourable, that is variation was not of an adaptive nature. This postulate was severely criticized even by the most orthodox adherents of Darwin's theory. For example, a famous German darwinist, Ernst Haeckel (1834-1919), supposed that environmental changes must cause adequate heritable variation (Haeckel, 1902). He proposed to reduce the mechanism of evolution to only two factors - heredity and adaptation. He understood heritable variation only as a result of environmental influence (climate, nutrition, and so on). We see that this is virtually pure lamarckism. In such a case, what is the novelty of Haeckel's "darwinism"? It seems to consist in the following. First, adaptations - that is, favourable heritable alterations - occur in not all competing individuals. Second, the value of these beneficial alterations is so low that they require accumulation by natural selection. Thus, the darwinism of Haeckel, as well as of the later Darwin himself, differed from lamarckism only quantitatively. In fact, returning to the fourth law of lamarckism, it can be criticised as being too categorical.
Perhaps one more mistake of the keen adherents of Darwin consists in their tendency to exaggerate - even deify - the "creative" capabilities of Selection, who sees everything, measures everything, so that no one hair, no one nucleotide pair can be left without careful examination. Such a viewpoint was to some extent akin to that of the founder of the theory himself. For example, in the "Origin of Species" he wrote: "natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being..." This drawback inherent to orthodox darwinism was realized and overcome by the outstanding contemporary evolutionist Motoo Kimura, who has complemented the theory of natural selection by his own "theory of neutrality" (Kimura, 1983).
A crushing blow to lamarckism was delivered by August Weismann. He demonstrated that the germ line cells separated extremely early from the other (somatic) cells of an organism. Therefore, regardless of how intensively a somatic organ is exercised, the result of training - even if somehow impressed on the chromosomes of the somatic cells - physically cannot be acquired by chromosomes in the generative cells. An inevitable consequence of this finding was that the individual experience of no organism could be inherited (Weismann, 1893). Thus Weismann had restored darwinism to a novel form purged of lamarckism - neodarwinism.
However, in the early 20th century these approaches had faced substantial difficulties associated with advances in a new science - genetics. In 1903 the Danish geneticist Wilhelm Johansen (1857-1927) clearly showed the ineffectiveness of selection in pure lines of the common bean. Such lines comprise individuals with nearly identical heredity. During a number of generations Johansen picked out and planted the smallest and the largest seeds. However, the mean weight of a seed in both lines remained unchanged (Johannsen, 1903). To neolamarckists this result was a devastating blow, since substantial individual variation turned to be non-heritable. At the same time neodarwinists had to face the problem, now out in the open: how does heritable variation occur?
The experience of classical genetics suggested that alteration of a gene was an extremely rare event. This had generated the widespread opinion that occurrence of selectively favourable changes was not mere accident. Controversy between geneticists and evolutionists alimentated many rather dubious theories directed to strengthening neolamarckist positions. The most scandalous was a theory by Trofim Lysenko, which was dominant in the USSR in the 1930s-50s. Here is a quotation from his work "About Heredity and its Variability" (Lysenko, 1944): "In all cases when an organism finds necessary conditions in the environment corresponding to its nature, development of the organism proceeds in just the same way as it occurred in previous generations of the same breed (the same heredity)... However, in the cases where organisms do not find the necessary conditions and are made to assimilate environmental conditions to some extent not corresponding to their nature, there occur organisms or separate parts of an organism's body different from the preceding generation. ... External environmental factors involved and assimilated by a living body become internal conditions, that is they become particles of the living body and for their growth and development demand food and environmental factors identical to themselves as they were in the past... Alteration of requirements, that is heredity of a living body, is always adequate to the action of environments, if these conditions are assimilated by the living body" (my italics - V.B.).
It is quite clear that formal genetics (morganism) and neodarwinism (weismanism) are incompatible with such ideas. The theory of Lysenko was discarded through the further development of genetics that resulted in an understanding of the nature of heredity and, therefore, an understanding of its variation. In 1930s-40s genetics had united with neodarwinism to give rise to the so called "Synthetic Theory of Evolution" capable of a reasonable explanation of evolutionary shifts (Huxley, 1942). It became clear that any natural population possessed a significant resource of heritable variation and therefore was ready for selection in any direction. Finally, one should not forget that evolution - to the man in the street - is an extremely slow process. Even the most rapid shifts of morphologic traits registered by a paleontologist do not occur faster than 10-20 millidarwins, one darwin corresponding to a change of a character's value by a factor of e per million years (e - the base of natural logarithms - is approximately equal to 2.718).
Thus, the only aim of natural selection consists in increasing the fitness of individuals. This can be achieved by different means, for instance, it could be by raising fecundity and simultaneously simplifying the structure of many organs - as do many parasites. Therefore Darwin's theory does not imply that selection acting at the level of individuals should bring about structural complication. At the same time a paleontologist studying the morphology of related species replacing each other in a series of geologic strata often observes unidirectional changes in size and complexity of some organs and structures.
It should be noted that a paleontologist's view of time has some peculiarities. As a rule he uses so called geological time, duration of which is determined by the height of a geological layer and the rate of its formation. This rate depends upon many factors, but there are methods for transforming geological into astronomic time. The latter is usually measured not by generations or years but by millions of years. Events which are synchronous from such a viewpoint may be separated by millennia or even tens of millennia.
When analyzing prolonged unidirectional trends, associated as a rule with enlargement and complication of morphologic structures, a paleontologist not infrequently comes to the conclusion that these macroevolutionary shifts proceed by themselves, promoted by some internal factors, not in relation to environmental changes but rather in spite of them. An altered habitat merely rejects from time to time some species which due to overdevelopment (or underdevelopment) of certain morphological structures lose their adaptivity. Thus, a paleontologist does not deny natural selection but considers it only as a sieve eliminating species represented by poorly viable or extremely specialized individuals.
While, according to Darwin, traits change by continual accumulation of very slight favourable deviations, a paleontologist does not take into consideration individual variation at all; that is, he completely ignores the so called creative role of selection. It should be noted that the paleontologist judges a species by the morphology of a few, often damaged specimens, so he is in practice unable to analyze the dynamics of microevolutionary shifts. It may seem that an absence of microevolutionary information should not be an argument against the creative role of selection. Nevertheless, the paleontologist has his reasons for ignoring microevolutionary changes.
First, the experience of field biologists suggests that morphological shifts do not always follow environmental changes. Second, one should not forget the persistent forms which do not alter their morphology for tens of millions of years in spite of radical environmental alterations - or at least significant changes of faunas. Finally, during the last decade the so called theory of punctuated equilibria has been widely and actively discussed in the literature (Gould, Eldredge, 1977; Stanley, 1982).
This theory is based on a rather typical pattern in the occurrence of individuals with similar morphology in different periods of geological time. It was found that individuals of very similar morphology and probably belonging to the same species may be constantly present in geological strata for several million years. Then for a short interval they "disappear", to reappear for further millions of years with a slightly changed appearance, so that they can be regarded as another species. Thus species morphology remains virtually unchanged for several million years, and this period is called stasis. Species transformation, that is, morphological alteration, occurs very quickly - from the paleontologist's point of view instantly - although this "instant" can last tens of thousands of years.
It should be noted that such a discontinuous (punctuated) pattern is far from being universal. Distributions of individuals in geological time frequently correspond better to the traditional, gradual model, that is, alteration of their morphology goes on continually - gradually. The idea of punctuated equilibria by no means contradicts darwinism since we have no idea at all what environmental changes took place in the periods of stasis and of species transformation. There are no reasons why species morphology should be altered by any particular environmental change: it is to be expected only if there exists an absolute correspondence between environments and species morphology. However, there is nothing absolute in the world. At the same time it cannot be said that the paleontological evidence mentioned above supports darwinism. This circumstance provides psychological justification for the constant attempts of paleontologists to explain macroevolutionary trends by invoking special dynamic factors acting independently of environmental changes.
It is typical of humans to find in all natural processes a manifestation of laws acting with absolute necessity. Even Democritus (c.460-c.370 B.C.) supposed that nothing takes place by accident but proceeds for some reason and necessity. Every day we can observe that movement of the macroscopic bodies around us is due to the action of relevant forces. These phenomena form the subject of mechanics, its laws being obeyed with amazing accuracy. A concept of force in mechanics is anthropomorphic since a man uses it in his everyday life to measure his own influence on bodies. And what is the reason for applying a force? - the anticipation of the result of this application in man's thought, in other words his purpose.
We have already mentioned that Aristotle was the first to introduce the idea of teleofactors as specific causes acting in Nature. It should be said that in doing this he rendered a disservice to natural sciences and especially biology. Even now the terms "aim" and "purposefulness" are often used in embryology and evolutionary theory in not at all a figurative or metaphoric sense. However sad it is, we should admit that up to the 20th century biologists appealled mainly to two types of causes while developing their models - forces and aspirations. The first to create this kind of model were philosophers. Idealist philosophers (including "nature philosophers") were apt to turn to aims and aspirations, materialist philosophers to forces and dynamic laws.
Let us begin with some representatives of classic German philosophy. For example, Friedrich Schelling (1775-1854) supposed that all living bodies possessed a specific property - tendency (Trieb) to organization, that is, aspiration to generate new forms (Schelling, 1907). According to Georg Wilhelm Friedrich Hegel (1770-1831) some absolute idea or spirit, in the course of dialectic self-development, was incarnated in the progressive series of forms of non-living and living matter (Hegel, 1817). For Arthur Schopenhauer (1788-1860) the ladder of creatures was a manifestation of a specific internal property of natural objects - thirst for life, or Schopenhauer's will (Wille) (Schopenhauer, 1836).
A French materialist philosopher Julien Offrey de la Mettrie (1709-1751) in his book 'L'homme - machine' explained perfection of living beings by the action of unperceived dynamic laws as reliable as those of mechanics. "... Just as by virtue of some physical laws it is impossible for a sea to avoid the rise and fall of the tide, similarly, due to certain laws of movement, there have formed eyes able to see, ears able to hear, nerves able to sense, a tongue either able or unable to articulate sounds depending on its organization and, lastly, the same laws have created an organ of thought" (Lamettrie, 1796).
Beginning with the 18th century, biologists and "nature philosophers" tried to find a force impelling living matter to improve in the course of the individual development of an organism. It should be noted that up to the late 18th century in embryology the idea of preformation was dominant. It implied that individual development of an organism consisted merely in proportional enlargement of an embryo. Such a view lead to somewhat absurd conclusions: for example one had to admit that in the sexual organs of adults there were present embryos which in their own sexual organs also had embryos, and so on. Nevertheless faith in the possibilities of the Omnipotent Creator was infinite.
Due to the works of embryologists of the late 18th and early 19th centuries (Wolf, Mekkel and especially Baer) the theory of preformation was discarded. Embryonic development became considered as the formation of complex from simple, organized from disorganized, differentiated from undifferentiated. Naturally there immediately arose the question of the factors underlying this process. Kaspar Friedrich Wolf (1734-1794) introduced a "special force" - vis essentialis - acting like forces in mechanics (Wolf, 1789). Lamarck spoke of a "life force" which "resulted in organizational complication and consequently progress". Karl von Baer (1792-1876) gave preference to the teleofactors of Aristotle, supposing an aspiration to the specified aim to be inherent to every living creature (Baer, 1876). An anthropologist Johann Friedrich Blumenbach (1752-1840) developed an idea of an organismal aspiration to the formational process (Blumenbach, 1791). Just the same feature was considered to be the main factor directing development of organisms by Matias Schleiden (1804-1881) - one of the founders of the cellular theory. He supposed that every organism in the course of ontogenesis tended to raise its own completeness as high as possible (Schleiden, 1845). Similar ideas were stated by the outstanding German botanists Alexander Braun (1805-1877) and Karl Naegeli (1817-1891) (Naegeli, 1884). The latter supposed an existence of directed process of complication of hereditary matter.
Many of the investigators just mentioned were inclined to the same idea: the prolonged or more intensive action of special factors governing individual development could result in the formation of more perfect organisms. This idea acquired its complete form in the concept of the famous German "nature philosopher" Lorenz Oken (1779-1851), who supposed the formational force acting in ontogenesis to be responsible for the ladder of living beings as well. Moreover, he believed that in the course of individual development different organisms aspired to achieve the human state, producing numerous forms corresponding to different stages in the development of the human embryo. In other words there existed the universal developmental path from an egg to an adult human being which could be terminated at any step (Oken, 1809-11).
One cannot deny that this idea has some rational core. In fact evolution can be considered as a very long chain of ontogeneses, therefore, any novelty must occur as an alteration in individual development. It is interesting to note that this undoubtedly true thesis often becomes a point of resolute departure from darwinism. According to Darwin significant alterations of morphology (typical of different species of the same genus) are accumulated by natural selection and consist of very slight, hardly visible shifts. According to another view large alterations of ontogenesis occur by virtue of some internal autonomously acting morphogenetic processes. Natural selection does not participate in creation of new living forms and only "judges" those which have occurred by themselves.
For example the contemporary Swedish biologist Soren Lovtrup (1974) believes that some internal epigenetic formational mechanism governing ontogenesis is the necessary and sufficient condition of an organism's existence, provided of course that it is not prohibited by the environment. An extreme expression of such a viewpoint is the idea of specific hereditary alterations - system mutations - instantly bringing about individuals ("hopeful monsters" in Goldschmidt's (1940) terms) virtually belonging to another species or even another taxon of a higher rank.
In a very clear form the concepts of the dynamic nature of evolutionary factors were represented in the theory of nomogenesis put forward by a famous Soviet ichthyologist, geographer and evolutionist Lev Berg. According to him "evolution of organisms is nomogenesis, that is development based on regularities. However, these regularities are not of a static, but rather of a dynamic nature, like laws controlling reversible processes such as gravitation, electrical and mechanical oscillation, or acoustic and electromagnetic waves" (Berg, 1922). These processes embrace the overwhelming majority of individuals inhabiting vast territories. Hereditary alterations proceed rapidly and have certain direction. Similar ideas were expressed by other paleontologists of the 20th century - Henry Farfield Osborn (1917, 1932), Otto Heinrich Schindewolf (1950), Pierre Teilhard de Chardin (1965). Phylogenetic development in one direction under the influence of aspiration or inner dynamic factors has acquired the name "orthogenesis". Teilhard de Chardin (1965) believed "orthogenesis to be dynamic and the only complete form of heredity."
Although ideas of special evolutionary forces and laws acting with strict necessity do not stand up to criticism from the viewpoint of modern genetics, their adherents do not give up. Nomogenesis is especially widespread among Russian evolutionists. One cannot help be amazed how strong is the belief in dynamic laws of Nature. Today much is known about properties of heredity and interaction of organisms with their environments. Everything appears to argue that if evolution follows any laws, they should be not dynamic but statistical. It means that any subsequent state of a biological system should be determined by the previous state - but not absolutely, rather in terms of probability.
Thus we see that all the evolutionary theories are embraced by three main models. The first model associates evolutionary progress with the action of teleofactors (aspiration to perfection), and the second with the action of internal forces inherent to the nature of living beings. The third denies the existence of such motive factors, and the very idea of progress is regarded with a certain scepticism.