EVOLUTION AS THE M EANS OF EXISTENCE OF LIVING MATTER

Transcription

1 Uroboros, or biology between mythology and philosophy ed. by W. Ługowski & K. Matsuno Wrocław 1998 Arboretum Pawet Grieb Polish Academy of Sciences Medical Research Centre Pawirtskiego 5, Warsaw, Poland EVOLUTION AS THE M EANS OF EXISTENCE OF LIVING MATTER 1. IN TRO D UCTIO N In 1980, British m athem atician John Little published a short paper entitled "Evolution: myth, m etaphysics or science?"1. Although it is m ore than fifteen years old by now, I believe it is still o f interest to evolutionary biologists and philosophers o f biology. In his article Little exam ines Karl Popper s w ell known claim that the D arw in s theory o f evolution is m etaphysical rather than scientific. Such a statem ent requires, how ever, clarification o f the term s "m etaphysical" as opposed to "scientific". W hile "m etaphysical" is frequently used as a synonym o f "pseudo-scientific", P opper uses this term to label any theory w hich is either not falsifiable, or does not provide m eans fo r generating precise and accurate predictions. H owever, in this sense, very few theories, indeed, can be described as being truly "scientific". There are, after all, m any theories or notions w hich are neither falsifiable nor have the exact predictive pow er and yet constitute the very canon o f contem porary "scientific thinking". A very good case in point is the concept o f realism according to which the external w orld exists outside our sensory experience. A concept as fundam ental to m odern science as this w ould seem alm ost by definition "scientific". And yet, as not falsifiable, it should properly be called, in keeping with Popper s definition, "m etaphysical". A pparently there are theories "m etaphysical" in the P opper s sense, w hich are scientific, or at least "scientific enough". The question, therefore, is w hether theory o f biological evolution (Darwinian, neo- D arwinian, or any other) is after all scientific despite being "m etaphysical" in the P opper s sense, o r is it m erely a myth, a m ental construct which one m ay or m ay not believe, depending on one s intellectual predilection. In other words, are contem porary theories o f biological evolution "scientific enough"? Little quotes P opper w ho have said that "neither Darwin nor any Darwinian, 1 J. Little, Evolution: myth, metaphysics, or science?, "New Scientist" 1980, 4 September, p

2 has so far given an actual causal explanation o f the adaptative evolution o f any single organism or any single organ". This, indeed, poses a problem since according to the general form ulation of D arw in s concept o f natural selection the survival o f the fittest can only be m easured post factum by observing the actual success o f survival. Such a form ulation sounds tautological and it can hardly be taken as the ultim ate explanation o f the process of evolution. A t the conclusion o f his article Little once m ore quotes Popper saying: "There is a reality behind this world as it appears to us, possibly a m anylayered reality, o f w hich the appearances are the outerm ost layers. W hat the great scientist does is boldly to guess, daringly to conjecture, w hat the inner realities are like. This is akin to m ythm aking". And perhaps this thought should guide us w hen we venture to fathom and, in a sense, explain the process o f biological evolution. W hat w e see as the "survival o f the fittest" is perhaps the outer-m ost layer o f reality. S houldn t we try to guess w hat the inner realities are like? Even if it will not m ake the theory o f biological evolution "scientific" in the Popper s sense... In the present paper I propose and discuss a general concept that the very nature o f "living m atter" creates the necessity for the continuous process o f biological evolution. I suggest, in other w ords, that biological evolution is the m eans o f existence o f "living matter". The D arwinian natural selection is thus seen as a m echanism best suited to explain certain aspects of biological evolution, although it m ay not be the only m echanism by w hich "living m atter" evolves and m aintains its existence. There is som e evidence indicating that in the course o f evolution organism s acquired new m eans o f evolving, that they "learned" how to evolve "m ore efficiently". The last and perhaps the ultim ate step in this "evolution o f Evolution" m ay be the ability to directly m anipulate the genetic m aterial (i.e., genetic engineering). H um an beings, please note, are living organism s too. But are we, hum ans, still the subject o f biological evolution? This is an im portant point w hich I will briefly refer to at the conclusion o f the considerations w hich follow. 2. ON TH E D EFIN ITIO N O F LIFE In the developm ent o f biology the concept o f evolution (i.e., o f a m ultistep process o f directional changes) em erged in opposition to the fam ous static concept o f C harles Linne (which, indeed, w as m ore "static" than the A ristotelian "Scala Naturae"). W hile in "P hilosophia botanica"2 Linne stated expressis verbis that the num ber o f species had not change since creation (and conse 2 C. Linne, Philosophia botanica, Stockholmiae 1751, p

3 quently a system of taxonom y should ju st try to reflect this fact), J.B. Lam arck3 underlined first o f all that living organism s (both alive and already extinct) are not a set o f unchangeable species but a continuum o f m inutely different form s, m ore com plex o f w hich had em erged from less com plex through the process o f "evolutionary change". The very sam e concept o f continuum was adopted by Darwin, and later by neo-d arw inists. W hat changed between Lam arck and D arwin was the location o f the driving force o f the evolutionary process, from Lam arckian "intrinsic desire fo r im provem ent" to Darwinian external "natural selection". Yet one question rem ains that has not been conclusively answered: is the existence o f all living organism s predicated upon the evolutionary process? In other words, is it possible to conceive o f living organism s that did not evolve by the D arwinian (or any other) m echanism? Before attem pting to answ er this question w e need to decide on a definition o f living organism s and that, in turn, entails providing a definition o f life. However, in spite o f m any attem pts to arrive at such definition, none adequate or generally accepted seem s to have been found yet. There is no consensus on how to answ er such questions, as "H ow we can ju stify and explain taking organs fo r transplants - such as a heart or kidneys - from a dead human body, these organs being ostentatiously alive? Is being alive the attribute o f a cell, o r an organism, or perhaps a population, or o f a species?" On the other hand it seem s perfectly clear that "living matter", i.e., the m atter o f which the living organism s are built, is clearly distinguishable from the non-living m atter on the basis o f its chem ical com position, cellular structure, m etabolism, selfreproductive ability, etc. W e m ay reasonably agree to define "living m atter" by a set o f such attributes (som e o f them are listed in Table I). M ay we, therefore, define life sim ply by the set of the above-m entioned attributes? One m ay argue that in fact such a definition is trivial, because it has only a broadly descriptive character and by no m eans helps to understand or explain the phenom enon o f life. Also, if w e artificially create and organize m atter in such a w ay that it possesses all "descriptive" attributes of life such as those listed in table I, w ould it really m ean that w e created "life"? The last question seem s to have no obvious answ er but we can easily circum vent the problem by incorporating into the definition o f "life" the fact that it has its own history. M ost scientists concerned with origin o f life agree that the process o f biogenesis w as driven by natural forces (there w as no "creator") and that it w as a one-tim e event, at least in the sense of one event (or one set o f events) o f biogenesis being sufficient to create life on Earth as a continuous phenom enon w hose existence can be dated back to that single occurrence. 3 J.B. Lamarck, Philosophie zoologique, Paris

4 Natural "living m atter" proved its ability to exist in changing environm ents for several billions of years. Therefore long-term ability o f continuous existence in changing environm ents m ay be added to the "descriptive" list as one more, though a very im portant one, attribute o f "real" "living matter". Life, as we know it, had em erged once and from that tim e it has been able to perpetuate itself despite frequent (in the geological tim e scale) and profound changes in environm ental conditions. Clearly, during these past tim es living organism s created a continuum o f form s, i.e., evolved. But does it m ean that biological evolution really w as a necessity? 3. LIFE IS IN TR IN SIC ALY E R R O R -PRONE PH ENOMEN O N The attributes o f "living m atter" listed in table I are essential constituents o f its property called "self-organization". Therm odynam ically self-organization can be defined as the capacity to preserve order, or, in other words, ability to accum ulate negative entropy. In general evolutionary processes, defined as gradual, directional change, are com m on throughout the universe but all presently known, w ith one exception, that o f life, are directed in the long term to w ards the increase o f entropy. In isolated areas entropy m ay be preserved or m ay even decrease fo r short periods o f tim e, but the general direction of change alw ays ultim ately leads, by virtue of the second law o f therm odynam ics, tow ards "less organized" form s o f matter. In the sea of inanim ate w orld's rising entropy life is an archipelago o f isolated islands o f "biological order" (cells and organism s). Once the cellular theory o f Schleiden and Schw ann gained general acceptance, biologists agreed to regard cell as a basic unit o f life. The next level in the hierarchy o f organization o f "living m atter" is organism (although m any organism s are unicellular), and the next one is population. Living cells and organism s are able to accum ulate "negative entropy", that is are endow ed with the ability to create and m aintain an orderly and "seem ingly purposeful" design. This is possible thanks to catalytic ("m achine-like") properties of proteins, w hich are structured in netw orks and cycles o f m etabolism. C ells and organism s are som etim es described as "self-organizing dissipative structures" to indicate, som ew hat counter-intuitively, that they are created and m aintained by the dissipative, entropy-producing processes4. It has been dem onstrated that the m aintenance of "biological order" within cells is m ade possible by the release o f heat energy from cells5. But still the question rem ains w hether such 4 1. Prigogine, G. Nicolis, A. Babloyantz, Nonequilibrium problems in biological phenomena, "Annals of the New York Academy of Sciences" 1974, v. 231, p B. Hess, M. Markus, Order and chaos in biochemistry, "Trends in Biochemical Sciences" 1988, v. 12, p

5 structures must evolve, and if they do, must they evolve by the Darwinian natural selection? Any kind of catalytic protein (enzyme) in a given cell has its own characteristic half-time, i.e., time by which one half of its molecules are dismounted and substituted by those newly synthesized. As time passes, every enzymatic molecule will progressively lose its catalytic activity in consequence of an array of chemical and physical interactions. Even if the primary structure of a protein would not change due to some chemical reactions (such as, e.g., oxidation of amino acid residues), protein molecule would still gradually loose its active conformation (will become "misfolded", or "physiologically senescent"). This necessitates recognition and elimination of damaged or "old" protein macromolecules and their substitution by those newly synthesized. Selective protein turnover in Eucaryota is determined by an universal mechanism, the so-called "ubiquitin-dependent proteolytic pathway"6. Some proteins are even specifically "marked" for relatively fast decomposition7. The limited duration of the catalytic activity is, therefore, the intrinsic property of catalytic proteins. The consequence of this, which is frequently overlooked, is the demand for their continuous breakdown and synthesis. In the absence of such a mechanism, the only conceivable alternative would be continuous biogenesis, repetitive synthesis of catalytic peptides de novo from the inanimate matter. However, the major breakthrough of biogenesis, i.e., linking protein synthesis to the much more stable "blueprint" preserved in DNA sequence, one that can replicate with high fidelity and undergo translation into protein structure, provided for stable "memory of the biological order". Once the primitive cells acquired the ability to memorize sequences of amino acids of their catalytic proteins in the form*of DNA helix which could be accurately copied, repetitive generation of catalytic peptides from inanimate matter was no more a requirement. Life become a continuous phenomenon. One of the basic processes which makes the maintenance of biological order possible is the phenomenon of molecular recognition. In the famous "Molecular biology of the cell" molecular recognition is characterized as follows: "The sequence of subunits in a macromolecule contains information that determines the three-dimensional contours of its surface. These contours in turn govern the recognition between one molecule and another, or between different parts of the same molecule, by means of a weak non-covalent 6 A. Hershko, A. Ciechanover, The ubiquitin system for protein degradation, "Annual Review of Biochemistry 1992, v. 61, p A. Varshavsky, The N-end rule, "Cell" 1992, v. 69, p

6 bonds"8. M olecular recognition is essential fo r all kinds o f processes which are involved in the generation and m aintenance o f biological order, including the transcription and translation of genetic inform ation, as w ell as DNA replication. However, "m olecular recognition can never be perfect. Because o f random factor in m olecular interactions, m inor side reactions are bound to occur occasionally. As a consequence, a cell continually m akes errors (...) M istakes could be avoided com pletely only if the cell could evolve m echanism s w ith infinite energy differences betw een alternatives. Since this is not possible, cells are forced to tolerate a certain level o f failure and have instead evolved a variety o f repair reactions to correct those errors that are the m ost dam aging"9. It should be added that repair reactions also cannot be perfect, by virtue o f the sam e chem ical principle, so that cells must, indeed, m ake m istakes. "On the other hand, errors [in m olecular recognition] are essential to life as w e know it. If it were not fo r occasional m istakes in the m aintenance o f D NA sequences, evolution could not occur1'10. This is a som ehow m isleading statem ent, because it im plicitly suggests that "biological order" w ithout m istakes is thinkable - w hile it is not. The difference is quite fundam ental, if w e consider the following: If the only source of random variations w ere errors (m utations) inflicted by harm ful environm ental interactions (ionizing radiation, etc.) or avoidable flaw s in the design of biological structures, cells and organism s w hich do not m ake m istakes and do not generate variability w ould be thinkable. But, because the "living m atter" has its particular m olecular design, the system o f biological recognition is error-prone and m olecular m istakes in the cells and organism s are not avoidable. M aintenance o f the biological order entails the existence, in the long run, o f som e kind o f m istake-correcting m echanism. O bviously, w hen errors are unavoidable, there m ust be som e m eans o f verifying their functional m eaning. N eo-d arw inian theory postulates that the verification is through the m echanism o f natural selection, i.e., the survival of the fittest. 4. TH E M YSTER Y OF A D A P TATIO N C harles Darwin w as a naturalist. His ingenious contention that organism s m arvellously fit to their environm ents and that the species gradually change w as based on pure naturalistic observations. His theory o f natural selection aim ed to explain how this apparent perfect fit - com m only found throughout the w orld o f fauna and flora - cam e about. However, he had no know ledge 8 B. Alberts, D. Bray, J. Lewis, M. Raff, K. Roberts, J.D. Watson, Molecular biology of the cell, 3 ed., New York 1994 Garland, p Ibidem, p Ibidem

7 about how organism s, or "living m atter" in general, m anage to "keep alive" and how adaptative traits, or any other biological properties, are inherited. For this reason his explanation w as in fact only descriptive. The concept o f natural selection seem ed, however, so adequate and general that in due tim e it seem ed to em brace all the great discoveries o f "reductionistic branches o f m odern biology, m olecular biology and genetics. The structure and function o f D N A and proteins, the m echanism s o f heredity and the role of m utations (random changes in D N A created by environm ental factors or by intrinsic infidelity of m olecular recognition processes), all these w ere thought to be com patible w ith the general concept o f "the survival o f the fittest". But the discussions on the m eaning and im plications o f the general notions of the theory of natural selection rem ained the dom ain o f naturalists. Am ong the general notions of the Darwinian theory the term that focused the m ost controversies and discussions w as that o f adaptation. A detailed analysis o f the m eaning o f this term was, fo r exam ple, provided by Richard C. Lewontin, P rofessor o f Zoology at Harvard University. A t the beginning of his 1978 article11 he wrote: "The m odern view o f adaptation is that the external w orld sets certain problem s that organism s need to solve, and that evolution by m eans o f natural selection is the m echanism for creating these solutions. Adaptation is the process o f evolutionary change by w hich the organism provides a better and better solution to the problem, and the end result is the state o f being adapted (...) Yet there is no end to adaptation." Later on he m odified the definition as follows: "W hen adaptation is considered to be the result of natural selection under the pressure o f the struggle fo r existence, it is seen to be a relative condition rather than an absolute one (...) The concept of relative adaptation rem oves the apparent tautology in the theory of natural selection (...) An analysis in w hich problem s o f design are posed and characters are understood as being design solutions breaks through this tautology by predicting in advance w hich individuals will be fitter". However, "evolution cannot be described as a process o f adaptation, because organism s are already adapted. Then w hat is happening in evolution?" In this context Lewontin recalls the concept known as the "Red Q ueen" hypothesis, o r "the hypothesis of environm ental tracking". According to this concept "environm ent is constantly decaying w ith respect to existing organism s, so that natural selection operates essentially to enable the organism s to m aintain their state o f adaptation rather than to im prove it." This is, indeed, an interesting idea, but it im plies that if the environm ent w ere to rem ain unchanged, no evolution w ould be necessary. 11 R.C. Lewontin, Adaptation, in: Evolution. A Scientific American book, San Francisco 1978 Freeman, p

8 Later on he says: "The current procedure fo rju d g in g the adaptation o f traits is an engineering analysis o f the organism and its environm ent", and his m eaning o f "engineering analysis" is purely naturalistic. An exam ple is the shape of a sponge optim ized fo r both m axim al feeding efficiency and the greatest resistance to predators. H ow such an optim ization could have occurred on the basis of random changes in the genetic m aterial, rem ains som ew hat perplexing. Let s recall one m ore fragm ent from Lew ontin s paper: "The diversity that is generated by various m echanism s o f reproduction and m utation is in principle random, but the diversity that is observed in the real w orld is nodal: organism s have a finite num ber o f m orphologies, physiologies and behaviors and occupy a finite num ber o f niches. It is natural selection, operating under the pressures o f the struggle fo r existence, that creates the nodes. The nodes are adaptative peaks, and the species or other form occupying a peak is said to be adapted". The explanation o f this "nodality" in term s o f random generation o f genetic variability w ould require assum ption that several different m utations should occur sim ultaneously to m ake it possible to jum p from one node to the other. Had the "living m atter" enough tim e to create the known diversity of species by testing all random ly generated com binations o f m utations? Lew ontin s paper show s the kind o f problem s "naturalists encounter with the term "adaptation". A pparently they all agree that som e state o f adaptation is a general attribute o f life (or "living m atter"). But are there organism s "better" or "w orse" adapted? Can adaptation be quantified? Does better (higher, tighter) adaptation guarantee the evolutionary success? Can one predict w hich organism s are better (higher, tighter) adapted to a given environm ent? Is there any "reference" that w ould m ake it possible to judge a priori w hich m odification w ill be successful? O r is there som e "inner reality" that we have not yet visited? 5. EVO LU TIO N OF TH E BIO LO G IC A L EV O LUTIO N Let s take a short look at the history o f life on Earth. Life originated on Earth som e 3,5 billion years ago. Then it took 2 billion years until the first eukaryotic cells appeared. M ulticellular plants and anim als em erged only som e 600 m illion years ago. From that tim e on, w ith relatively short periods o f abrupt reduction o f diversity due to great extinction episodes, the num ber o f species inhabiting the Earth increased in tim e, the grow th in som e stretches o f tim e being exponential. The first exponential diversification is known to have occurred during O rdovician, the second started in Triassic and is evident until the pres -204-

9 ent tim e 12. W hy did it took so long to design Eucaryota? W hy did diversification proceed at the accelerated pace despite the organism s becom ing m ore com plex? O ne can intuitively predict that in com plex organism s single m utations w ould very rarely be adaptative. The m ore specialized and optim ised the organism s are, the m ore com plicated sets o f sim ultaneously occurring m utations w ould be required to cause a jum p from one adaptative node to the other. If m utations occur random ly, the likelihood o f creating an adaptive set of m utations w ill decrease. Let's look again to the concepts em erging from m odern "reductionistic" branches o f biology. It has been determ ined that the structures o f som e proteins playing critical role in the m aintenance o f biological order are conserved fo r m illions, or even billions o f years. An exam ple is the gene o f triosephosphate isom erase, w hich internal structure (including five introns, i.e., noncoding sequences) suggests that it w as preserved fo r 3 billion years13. The explanation is that alm ost any m utation in this im portant gene w as lethal. Apparently som e fundam ental biological inventions w ere so fit that they could have never been changed. O thers, however, w ere apparently "less ingenious" inventions and could have been changed m ore frequently. But were these changes really random? The num ber o f proteins w ith different prim ary structures (am ino acid sequences) is unim aginably high. From 20 types o f am ino acid residues m ore than different proteins can be form ed. However, only a sm all fraction o f polypeptide chains w ould adopt a stable conform ation w hile the others would have m any different conform ations (none of them preferred) and their chem i cal (catalytic) properties w ould rem ain undefined and useless from the point o f view o f creation o f "biological order". For this reason new proteins usually evolved by alterations o f the old ones. One o f the new protein generation m echanism is that o f recom bination o f the pre-existing polypeptide dom ains o f proven stability and "biological usefulness". This is achieved by m ultiplying and com bining the coding sequences o f genes (exons)14. The genom es o f Eucaryota generally contain m any types o f the so-called "transposable elem ents", D N A sequences w hich can increase genom e diversity by causing 12 M. Benton, Diversification and extinction in the history of life, "Science" 1984, v. 268, p W. Gilbert, M. Marchionni, G. McKnight, On the antiquity of introns, "Ceir 1987, v. 46, p C. Blake, Exons and the evolution of proteins, "Trends in Biochemical Science" 1983, v. 8, p

10 duplication and m ovem ent of exons (exon shuffling)15. It is highly possible that the appearance and evolution o f transposable elem ents o f the genom e provided the m eans fo r random ly exchanging the pre-selected exons encoding the polypeptides o f proven usefulness in creating biological order. Interestingly, 10% o f the hum an genom e consists o f only two kinds o f transposable elem ents (the L1 sequence w hich encodes reverse transcriptase, and the Alu sequence). T heir em ergence and m ultiplication, o f relatively recent vintage, could have contributed to the accelerated evolution leading to the creation of the hom inids and hum ans16. As m entioned above, the ability o f organism s to evolve w as not constant over tim e. A ccording to paleobiological data, the rate o f diversification o f "living m atter" m ore or less continuously increased. The plausible explanation provided by m olecular biology is that the genom e of the Eucaryota evolved not only as the genetic determ inant o f the state o f adaptation, or the level o f fitness. A pparently its ability to evolve, or in other w ords its ability to generate - in ever shorter periods o f tim e - m ore tight adaptation to increasingly sharply defined ecological niches also evolved. Thus, the biological evolution is a m ulti-dim entional phenom enon. It operates at m any different levels. Procaryota "learned" how to evolve to rem ain fit in the changing environm ents and preselected a class o f genes encoding polypeptide chains that are useful in m aintaining "biological order". T heir evolution w as probably driven by purely random m utations, and this is the reason w hy it took so long to create Eucaryota. Eucaryota learned how to evolve m ore efficiently and in shorter tim e probably by "inventing" the transposable elem ents facilitating exon shuffling. This is w hy they w ere able to create, in the relatively short tim e, the unprecedented diversity o f species tightly adapted to the narrow ly defined ecological niches. M ost recently, the rate o f evolutionary change speeded up in prim ates, leading to the origin o f hom inids and, finally, hum ans. The difference in the protein m akeup betw een hum ans and som e prim ates is approxim ately 3%, but the adaptative difference is enorm ous. It is highly unlikely that this enorm ous evolutionary progress resulted from random m utations and the m echanism o f natural selection. 6. H O M O S A P IE N S - N E W PERSPECTIV E S FOR EVO LUTIO N At the beginning o f the present article I m entioned a rather im portant fact that hum an beings are also living organism s. W e certainly share with other 15 J.D. Finnegan, Eukaryotic transposable elements and genome evolution, "Trends in Genetics" 1989, v. 5, p P.L. Deininger, G.R. Daniels, The recent evolution of mammalian repetitive DNA elements, "Trends in Genetics" 1986, v. 2, p

11 17 W. Kunicki-Goldfinger, Dziedzictwo i przyszłość [Heredity and futurę], W arszawa 1976 PW N. species o f living organism s the sim ilarity o f chem ical com position and design, w e also operate on the basis o f the sam e therm odynam ic principles as selforganizing dissipative structures. But are we, hum ans, subjects o f the process o f biological evolution? This is a highly controversial point and will be touched upon only very briefly. Evolutionists, by and large, try to avoid giving definitive answ ers to such a question. The opinions o f those few w ho dared to discuss this problem w ere extrem ely diverse. Som e authors w ere and are trying to prove that hum an populations are subject to natural selection in the Darwinian sense (m eaning "survival o f the fittest"). O thers say that, as fa r as contem porary populations o f Homo sapiens in the w ell developed countries are concerned, the evolutionary process either has stopped, or is about to stop. An exam ple o f this w ay o f thinking is given by the Polish m icrobiologist W ładysław G oldfinger-k unicki, w ho wrote: "H um ans are specialized species, although in principle the specialization concerns only one function - thinking (...) Biological evolution o f the hum ans, as it seem s, is therefore closed for very long, if not forever"17. Is it really? If w e assum e, along the line o f reasoning put forth in the preceding chapters, that the real subject o f the evolutionary process by natural selection is the efficiency o f com m unication betw een organism s and their environm ent, w e w ill easily com prehend the very basic difference between the non-hum an species and hum ans. The m echanism o f natural selection operates as if the environm ental conditions and their change w ere given a priori, or at m ost were being influenced (changed) by the evolving species in a purposeless, unpredictive m anner. P urposeful interventions (such as creation o f artificial environm ent by nest form ation, etc.) are o f negligibly sm all m agnitude com pared to the pow ers o f Nature. A t the sam e tim e the only source o f adaptative variability are m utational changes in the genetic m aterial. Homo sapiens, thanks to several unique properties (such as abstract thinking and language, com plicated social structuring o f populations, spatial and tem poral accum ulation of know ledge and technology, etc.) attained the ability to purposefully reshape its external environm ent. The actions o f hum an species are already global in scope and its pow ers begin to com m ensurate w ith those o f Nature. It m ay be debated w hether the environm ental reshaping is really purposely executed, but the prerequisites o f such "adroit" actions, i.e., technological potential to create artificial but "biologically friendly" external "N ature-independent" environm ents do, indeed, exist. Furtherm ore, technical m eans o f deeply influencing the w orking s o f the hum an body on the cellular level, including first at -207-

12 tem pts to purposefully change (or, rather, repair) the genetic m aterial, seem to be a m atter o f not too distant future. All these seem to give credence to the notion that Homo sapiens ceased to be a subject of natural selection, at least in the Darwinian sense. H um an survival shall not be restricted to the "fittest", the "less fit" individuals shall be m edically treated and cured including having their genes repaired. H owever, this will, by no m eans, be the end o f evolution. Even if w e assum e that the genetic pool o f Homo sapiens w ill be som ehow purposefully stabilized, so that the evolutionary process defined in term s o f population genetics (i.e., as the frequency o f genes in the population genetic pool) w ill be term inated, m any other aspects o f the very com plex relationship between hum an populations and their environm ents will, out o f necessity, continue to change at an everincreasing expenses o f energy and resources. W hile this seem s to hail the advent o f a new strategy o f evolution, it certainly does not im ply the end o f the evolutionary process itself

13 Table I The attributes of "living m atter" 1. C hem ical com position 1. Elem entary analysis Biogenic elem ents: C.H.O.N.S.P O ther necessary: CI.Ca.K.Na.Fe.M g M icroelem ents: B.M n.zn.c u.m o.c o.j.f (A ltogether only < 25 % o f elem ents abundant on earth 2. M olecular Structure Carbon chains and rings. M acrom olecules: Proteins built o f am inoacids N ucleic acids built o f nucleotides 3. M olecules and supram olecular structures dissolved or dispersed in w ater II. Spatial design o f m olecules M acrom olecular aggregates C om partm entation by unit m em branes Cell as the unit structure generating biological order III. Tem poral design o f cells Biological order is m ade possible by the relaese o f heat energy from cells Cells obtain energy by the oxidation of reduced polycarbon m olecules and conserve it in the from of ATP The hydrolysis of ATP generates biological order through m olecular recognition processes Enzym e-catalysed reactions are linked in sequences (chains or cycles) which are tightly regulated -209-