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ARTICLE PHILOSOPHIE ZOOLOGIQUE - 200: LAMARCK IN RETROSPECT KAMALES KUMAR MISR A* J. B. Lamarck is considered as one of the renowned evolutionists. He was the first scientist to explain evolution as a vertical phenomenon and considered man as the end product of evolution. Lamarck, originally a believer in constant world, became an evolutionist after studying the fossil and recent mollusks of France in the year 1799. Lamarck published his book Philosophie Zoologique in 1809 and is being misunderstood till today. It is time to evaluate Lamarckian perception from present day concepts of evolution. The paper depicts his personal life, his emergence as an evolutionist, his contribution on evolution, and post-Lamarckian discussions. Moreover, Lamarckism is analyzed from the angle of various inheritance systems. The idea of Lamarck is also addressed in the light of Baldwin effect, genetic assimilation, somatic selection hypothesis, internal selection, gene duplication, and evolutionary novelties. Lastly, an evolutionary model is proposed to elucidate Lamarckian concept based on the contributions on modern evolutionary modalities. Introduction D escent of complex organisms with modifications is the central theme of evolutionary theory which moves with the time. Evolutionary thoughts are constantly enriching our knowledge time and again. The central purpose of evolutionary biology is to provide a rational explanation for the gradual appearance of extraordinary complex and intricate organization of all kinds of living forms. A long argument continues to address the mechanism of evolution. As Mayr1 viewed that a true theory of evolution must postulate a gradual transformation of one species into another. Analysis of the history of evolutionary theories reveals that J. B. Lamarck should be considered as a true “First Evolutionist”. Background of a Naturalist Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck was born on August 1, 1744, in the village of Bazentin-le-Petit, Picardie, in the north of France in an impoverished aristocratic family. He was the eleventh child * 198 Department of Zoology, Bethune College, 181 Bidhan Sarani, Kolkata 70 006, Email: [email protected] of his father Philippe Jacques de Monet de La Marck (died in 1759) and mother Marie-Françoise de Fontaines de Chuignolles. His family had with a centuries-old tradition of military service in the French army. Lamarck’s eldest brother was killed in combat at the Siege of Bergen-op-Zoom, and two other brothers were still in service when Lamarck was in his teenage years. He was admitted to the Jesuit seminary at Amiens around 1750s. After the death of his father, Lamarck bought himself a horse, and rode across the country to join the French army, which was in Germany in the summer of 1761. Lamarck showed great physical courage on the battlefield in the Pomeranian War with Prussia, and he was even nominated for the lieutenancy. Lamarck’s company was left exposed to the direct artillery fire of their enemies, and was quickly reduced to just fourteen men and no officers left. One of the men suggested that the puny, seventeen year-old volunteer should assume command and order a withdrawal from the field; but although Lamarck accepted command, he insisted they remain where they had been posted until relieved. When their colonel reached the remains of their company, this display of courage and loyalty impressed him so much SCIENCE AND CULTURE, MAY-JUNE, 2011 that Lamarck was promoted to officer on the spot. However, when one of his comrades playfully lifted him by the head, he sustained an inflammation in the lymphatic glands of the neck, and he was sent to Paris to receive treatment. He underwent a complicated operation, and continued his treatment for a year. He was awarded a commission and settled at his post in Monaco. After working as a bank clerk in Paris for a while, Lamarck began to study medicine and botany and in Monaco he encountered Traité des plantes usuelles, a botany book written by James Francis Chomel. Lamarck was getting a reduced pension of 400 franc and he wanted to pursue a profession. He studied medicine for four years, but gave it up under his elder brother’s persuasion. He was interested in botany, especially after his visits to the Jardin du Roi, and he became a student under Bernard de Jussieu, a notable French naturalist. Under Jussieu, Lamarck spent ten years studying French flora. In 1778, he published some of his observations and results in a threevolume work, entitled Flore française. The book received great acclaim, in part thanks to the support of Buffon. Georges-Louis Leclerc, Comte de Buffon mentored Lamarck and helped him in getting membership to the French Academy of Sciences in 1779 and a commission as a Royal Botanist in 1781 at the royal botanical garden, the Jardin des Plantes, which was not only a botanical garden but a center for medical education and biological research. The job helped him to travel to foreign botanical gardens and museums. In 1788, Buffon’s successor at the position of Intendant of the Royal Garden, Charles-Claude Flahaut de la Billaderie, comte d’Angiviller, created a position for Lamarck, with a yearly salary of 1,000 francs, as the keeper of the herbarium of the Royal Garden. In his two years of travel, Lamarck collected rare plants that were not available in the Royal Garden, and also other objects of natural history, such as minerals and ores, that were not found in French museums. Aside from a stint as tutor to Buffon’s son during a tour of Europe in 1781, Lamarck continued as an underpaid assistant at the Jardin du Roi, living in poverty. In 1793, Louis XVI and Marie Antoinette went to the guillotine, the old Jardin des Plantes was reorganized as the Musée National d’Histoire Naturelle (National Museum of Natural History), which was to be run by twelve professors in twelve different scientific fields. Lamarck, who had called for this reorganization, was appointed a professor of the natural history of insects and worms (that is, of all invertebrates), a subject he knew nothing about. Lamarck received the official title of “Professeur d’Histoire naturelle des Insectes et des Vers”, with a salary of nearly 2,500 francs per year. On September VOL. 77, NOS. 5–6 26, 1794, Lamarck was appointed to serve as secretary of the assembly of professors for the museum for a period of one year. Personal Life Lamarck married and widowed four times. On August 8, 1778, he married Marie Anne Rosalie Delaporte. Lamarck’s first son, André, was born on April 22, 1781, and he made colleague André Thouin the child’s godfather. On January 7, 1786, his second son, Antoine, was born, and Lamarck chose Antoine Laurent de Jussieu, Bernard de Jussieu’s nephew, as the boy’s godfather. On April 21 of the following year, Charles Rene, Lamarck’s third son, was born. René Louiche Desfontaines, a professor of botany at the Royal Garden, was the boy’s godfather, and Lamarck’s elder sister, Marie Charlotte Pelagie De Monet was the godmother. Lamarck’s wife gave birth to three more children before dying on September 27, 1792. The following year on October 9, he married Charlotte Reverdy, who was thirty years his junior. In 1797, his second wife Charlotte died, and he married Julie Mallet the following year; she died in 1819. He is rumored to have married (and been widowed) a fourth time, but no documentary evidence exists to support this. The two daughters who attended his deathbed were left penniless at his death; one surviving son was deaf and incapable and another was insane. Only one son, Auguste, was financially successful as an engineer, and only he went on to marry and have children himself. Pre-Lamarckian Thoughts Pre-Lamarckian heritage have no distinct bearings on evolutionary thinking of man. Impact of religion eclipsed evolutionary thinking, because there was a contradiction between God and evolution. Researches on physics, cosmology, geology, etc. dominated the scientific fields. There was no conceptual proposition in biological sciences. Buffon and Linnaeus were two great naturalists in eighteenth century. The seventeenth and eighteenth centuries experienced an almost total revolution in man’s concept of nature. This was the ‘age of reason’. Peoples tried to understand reasons behind everything. Discoveries in various fields, especially on physical laws, infinity of time and space, cosmological evolution, discredited the Bible as a source of scientific explanation. Further, discoveries in the biological sciences too posed serious challenges to the creationist-interventionist interpretation, which include fossil evidence, heterogeneity of flora and fauna, propositions of Linnaean hierarchy, adaptability of organisms, etc. 199 Two major problems demanded scientific explanation during pre-Lamarckian period 1. 1. The origin of diversity with seemingly orderly arrangement in a natural system. 2. Superb adaptation of all organisms to each other and to their surroundings. More and more problems were identified about the discontinuity between species and higher categories, extinction and survival of species, existence of vestigial organs and the role of God. Now, creationism became an insignificant solution to the scientific community. Emergence of an Evolutionist In his initial days, Lamarck was originally an essentialist. He used to belief the concept of constant world. Originally he was not a thinker on evolution although the term was in the air. In his initial discourse (for the year 1799) as a professor of the ‘inferior animals’ (later known as ‘invertebrates’, the term coined by Lamarck himself), Lamarck believed that species are unchanging and there is no possibility of evolution. Interestingly, in the next year discourse, Lamarck came with essential points of his new evolutionary theory which was further explained in his book 2. What had induced Lamarck in changing his idea at the age of 55 years? As Mayr1 observed that an old man had ‘to abandon is previous world view and replace it by one that is so revolutionary that it had not been held by anyone previously’. From the late 1790s, Lamarck took over the charge of mollusks collection and carefully studied both the fossil and recent mollusks in the Paris Museum after the death of his friend Bruguière 3. He observed that many of the living mussels and marine mollusks had analogues among fossil species. He found that the modern species extended far back into the Tertiary strata and he established chronological series terminating in a recent species. This observation led Lamarck to think about that many phyletic series had undergone a slow and gradual change throughout time 1. During the studies on comparative anatomy of animals in Paris Museum, he found discontinuities among the various morphological types, insects, mollusks, worms, vertebrates, etc. and thought separate graded series should exist for each category. “I speak of an almost irregularly graduated series of the principal groups (masses) such as the great families; a series which assuredly exists among the animals as well as plants; but which, when the genera and particularly the species are considered, forms in many places lateral ramifications, the endpoints of which are truly isolated” (Discours XIII: 29) 4. In his book he 200 recognised two entirely separate lineages of animals, one leading from the infusorians to the polyps and radiarians, the other one, containing the majority of animals, arising from worms (Fig. 1). Later, Lamarck 5 recognised an even much larger number of separate lineages 6. Infusorians, Polyps, Radiarians Worms Annelids, Cirrhipedes, Molluscs Insects, Arachnids, Crustaceans Fishes, Reptiles Birds Amphibian Mammals Monotremes Cetacean Mammals Unguiculate Mammals Ungulate Mammals Figure 1. Lamarck’s figure ‘showing the origin of the various animals’ (Philosophie zoologique, p. 179). What had disturbed Lamarck’s thinking was the problem of extinction. Origin and extinction were the then central theme of scientific debate. Scientists and elite peoples were believer in constant and created world, thus they could not explain properly the facts of extinction and new origin. Several explanations were put forward. Firstly, extinct animals are those that were killed by Noah’s Flood or some other catastrophe. Second explanation was that the extinct species might be surviving somewhere in unexplored areas of Earth. Thirdly, it is thought that it is the work of man. Lamarck thought that extinction is only a pseudo-problem. According to him, “fossils … might have changed since that time and have been converted into the similar species that we now actually find?” 2 (p. 45). Lamarck thought that no organism ever extinct; … simply drastic transformation took place with change beyond recognition7. He emphasised that evolutionary change was the solution to the problem of extinction. His idea on evolutionism had strong support from his earlier geological studies 8 . Lamarck’s logic was that since a species is in complete harmony with its environment and since the environment constantly changes, a species must likewise change forever in order to remain harmonious balance with its environment. This is the basic philosophy of evolution which is not acceptable to now a day’s non-Darwinist. Lamarck viewed SCIENCE AND CULTURE, MAY-JUNE, 2011 it from another angle, that it would be possible for an intelligent creator to design a perfect organism in a static world of short duration, but in a constantly changing environment (drastic and catastrophe too) how could species have remained perfectly adapted to such changing scenario? Lamarck had clearly recognised the importance of the environment and the adaptation of the organism. Contribution of Lamarck In his first six years as professor, Lamarck published only one paper, in 1798, on the influence of the moon on the Earth’s atmosphere. Lamarck began as an essentialist who believed species were unchanging; however, after working on the mollusks of the Paris Basin, he grew convinced that transmutation or change in the nature of a species occurred over time. He set out to develop an explanation, and on 11 May 1800 (the 21st day of Floreal, Year VIII, in the revolutionary timescale used in France at the time), he presented a lecture at the Muséum national d’histoire naturelle in which he first outlined his newly developing ideas about evolution. In 1801, he published Système des Animaux sans Vertebres, a major work on the classification of invertebrates. In the work, he introduced definitions of natural groups among invertebrates. He categorized echinoderms, arachnids, crustaceans and annelids, which he separated from the old taxon for worms known as Vermes. Lamarck was the first to separate arachnids from insects in classification, and he placed crustaceans into a separate class from insects. His classification of the mollusks was far in advance of anything proposed previously. Lamarck broke with tradition in removing the tunicates and the barnacles from the Molluska. In 1802 Lamarck published Hydrogéologie, and became one of the first to use the term biology in its modern sense 9. In Hydrogéologie, Lamarck advocated a steady-state geology based on a strict uniformitarianism. He argued that global currents tended to flow from east to west, and continents eroded on their eastern borders, with the material carried across to be deposited on the western borders. Thus, the Earth’s continents marched steadily westward around the globe. Lamarck published Recherches sur l’Organisation des Corps Vivants in 1802, where he drew out his theory on evolution 8. He believed that all life was organized in a vertical chain, with gradation between the lowest forms and the highest forms of life, thus demonstrating a path to progressive developments in nature. Lamarck published a series of books on invertebrate zoology and paleontology. VOL. 77, NOS. 5–6 Of these, Philosophie zoologique, published in 1809, most clearly states Lamarck’s theories of evolution. The first volume of Histoire naturelle des Animaux sans vertèbres was published in 1815, the second in 1822. He even found time to write papers on physics and meteorology, including some annual compilations of weather data. Lamarck also anticipated the work of Schleiden and Schwann in cell theory. During his lifetime Lamarck became controversial, attacking the chemistry proposed by Lavoisier. In his own work, Lamarck had favored a traditional theory based on four elements 6. He also came into conflict with the widely respected palaeontologist Georges Cuvier, who was not a supporter of evolution. Lamarck’s New Paradigm Lamarck felt that two well known phenomena in the world of organisms, which were originally, raised earlier, need careful explanation. Animals show a graded series of “perfection” : Lamarck understood the gradual increase in “animality” from the simplest animals to those with the most complex organization, culminating in man. This idea he had developed from studies on mollusks. The amazing diversity of organisms : Anything possible need has effectively taken place. “After a long succession of generations…….individuals, originally belong to one species, became at length transformed into a new species distinct from the first” 2 (pp. 38-39). “These changes only take place with an extreme slowness, which makes them always imperceptible” 2 (p. 30). Lamarck’s Theory First law: “In every animal …. , the more frequent and sustained use of every organ gradually strengthens, develops and enlarges that organ, and gives it a strength proportionate to the length of time it has been used; while the constant disuse of such an organ imperceptibly weakens and deteriorates it, progressively diminishing its faculties until finally disappears” 2 (p. 113). Second law: Inheritance of acquired characters. “Everything which nature has caused individuals to acquire or lose as a result of the influence of environmental conditions to which their race has been exposed over a long period of time – consequently, as a result of the effects caused either by the extended use (or disuse) of a particular organ…. is conveyed by generations to new individuals descending therefrom, provided, that the changes acquired are common to both sexes, or to those 201 which produce the young” 2 (p. 113). He stated that “with regard to living bodies, it is no longer possible to doubt that nature has done everything little by little and successively” 2 (p. 11). Misunderstanding Injudicious readers of Lamarck’s work time and again misunderstood him by the term ‘besoin’ into ‘want’ instead of “need”, and a neglect of Lamarck’s carefully developed chain of causations from needs to efforts, to physiological excitations, to the stimulation of growth and eventually to the production of structures 1. Even Darwin wrote to J. D. Hooker on 11 January 1844 “Lamarck nonsense of … adaptations from the slow willing of animals” because he read mistranslation of the word besoin in to ‘want’ instead of ‘need’, and Lamarck’s careful explanations. Serious misunderstanding about Lamarck’s paradigm is that the idea of a direct induction of new characters by the environment. Lamarck himself rejected this interpretation: “I must now explain what I mean by this statement: The environment affects the shape and organization of animals, that is to say that when the environment becomes very different, it produces in the course of time corresponding modifications in the shape and organization of animals”. Lamarck wrote, it is true, if this statement were to be taken literally, “I would be convicted of an error; for, whatever the environment may do, it does not work any direct modification whatever in the shape and organization of animals” 2 (p. 107). The above statement shows that Lamarck was very much aware about the ecological impact in the evolutionary process. The list of evolutionists prior to Lamarck was believer in static world. Lamarck replaced this concept of world by a dynamic one and explained that entire balance of nature was constantly in flux. Lamarck was the first man to bridge the evolutionary gap by considering man as the end product of evolution even before the discovery of a hominid or even a primate fossil. He envisaged that “some quadrumanous animals, especially one of the 202 most perfect of them ……use their feet only for walking and to give up using their hands like feet…..that these quadrumanous animals would at length be transformed into bimanous, and their thumbs on their feet would cease to be separated from the other digits when they use their feet for walking” having upright posture “to command a large and distant view” 2 (p. 170) …. “an animal organization approaches that of man the more perfect it is” (p. 171). The strong critics of Lamarck, Georges Cuvier refuted the theory. At that time no one could expect himself to be in a fossil lineage. Cuvier died in 1832 and first hominid fossil (Pliopithecus) was not discovered until 1837. This is imaginative Lamarck, the first perfect evolutionist. World between Lamarck and Darwin Philosophie zoologique was a sign of the first breakthrough to evolutionism. The concept depicted in this book was refuted time and again until 50 years when Darwin came with substantial evidence. Darwin had burgeoning facts at his disposal of the scientific contribution in biology to prove evolution from various angle. Still none had accepted the theory of evolution unconditionally. Most of the contemporary scientists agreed to some of the contents of the complete theory. Table 1 shows how far close the views of Lamarck and Darwin was and contemporary scientists. Six major theories could be recognized in between propositions of Lamarck and Darwin 1. Most of these theories were controversial, which either state about the inheritance or effect of use and disuse (e.g. orthogenesis, aristogenesis, mutationism, direct induction, stochastic variation, saltationism, etc.). TABLE 1. Comparison of Evolutionary theories by contemporary evolutionist (modified after Mayr, 1991). Evolution as such Common descent Gradualness Populational speciation Natural Selection Lamarck Yes Yes Yes Not spelt Not explained Cuvier Yes Sometimes No No No Darwin Yes Yes Yes Yes Yes Haeckel Yes Yes Yes ? Partly Neo-Lamarckian school Yes Yes Yes Yes No T. H. Huxley Yes Yes No No No de Vries Yes Yes No No No Weismann Yes Yes Yes ? Yes T. H. Morgan Yes Yes No No Unimportant Synthetic theory Yes Yes Yes Yes Yes SCIENCE AND CULTURE, MAY-JUNE, 2011 Baldwin effect : The Baldwin effect, also known as Baldwinian evolution or ontogenic evolution, is a theory of a possible evolutionary processes 10. The Baldwin effect functions in two steps. In the first step, phenotypic plasticity allows an individual to adjust to a partially successful mutation, which might otherwise be utterly useless to the individual. The second step, if enough time is provided, evolution may find an inexorable mechanism to replace the plastic mechanism 11. Morgan12 and Osborn 13 independently arrived at the similar ideas, which explained that phenotypic plasticity is the ability of an organism to adapt to its environment during its lifetime. Pleiomorphism or “phenotypic plasticity” is a phenomenon in which a given genotype may develop different states for a character or group of characters in different environments due to “genotype-environment interaction”. This effect is similar to the concept of “canalization” 14, which describes the containment or limitation of phenotypic variation by developmental mechanisms. He added that a trait can be canalized against environmental disturbance, genetic perturbations, such as mutations, or both. Post-Darwinian Lamarckism Some critics of Charles Darwin tried to explain organic evolution on the basis of Lamarckian concept. Packard in 1884 proposed a term “neo-Lamarckism”, which covered a number of heterogeneous ideas 15. Most of the so-called neo-Lamarckian views (theories) dealt with mental forces. Interestingly, no two neo-Lamarckians had the same views, thus a consensus “Neo-Lamarckism” was never established. The important neo-Lamarckian views were, Geoffroyism, psycho-Lamarckism, etc. All neo-Lamarckians supported the inheritance of acquired characters and believed that something experienced and gathered by one generation could be transmitted to the next generation and subsequently heritable 16 . Until mutation and recombination were considered to be the principal forces in evolution, neo-Lamarckian explanation for adaptation was favoured. Proof of genetic material as causative force in evolution resulted in the speedy shifting of neoLamarckians to Darwinism. Genetic assimilation : After the establishment of Biological or Synthetic Theory (Modern Synthesis) (19361950), Waddington 17,18 proposed the idea of genetic assimilation as “a process by which a phenotypic character, which initially is produced only in response to some environmental influence, becomes, through a process of selection, taken over by the genotype, so that it is found even in the absence of the environmental influence which had at first been necessary.” Waddington 18 further VOL. 77, NOS. 5–6 pointed out that a combination of orthodox Darwinism and orthodox embryology can give the results that look like the inheritance of acquired characteristics and environmentally-induced genetic assimilation can produce rapid evolutionary change as well as speciation. Later, a number of experiments approved the concept. The combination of organic selection and orthoplasy (direct phenotypic evolution) is now commonly referred to as the “Baldwin effect.” Alternately, Waddington’s genetic assimilation is a process whereby an environmentally induced phenotype, or “acquired character,” becomes canalized through selection acting upon the developmental system. Genetic accommodation is a modern term used to depict the process of heritable changes that occur in response to a novel induction. Genetic accommodation is a key component of the Baldwin effect, and genetic assimilation is a type of genetic accommodation 19. Somatic selection : Other explanations include ‘somatic inheritance of acquired character’ 20, 21 and hormonally mediated inheritance 22. Steele and his colleagues explained why homologous DNA sequences from the VDJ gene regions of parent mice were found in their germ cells and seemed to persist in the offspring for a few generations. The mechanism involved the somatic selection and clonal amplification of newly acquired antibody gene sequences that were generated via somatic hyper-mutation in B-cells. The mRNA products of these somatically novel genes were captured by endogenous retroviruses of B-cells and were then transported through the blood stream where they could breach the soma-germ barrier (Weismann barrier) and retrofect (reverse transcribe) the newly acquired genes into the cells of the germ line. Lamarck in Recent Perspective Two aspects in Lamarckism are logical and noncontroversial i.e. evolution is vertical and is gradual. The major problem in the theory is the process of inheritance. The literal heading of the theory (second law) was “inheritance of acquired character”. No doubt that the establishment and subsequent inheritance of traits is of utmost importance in organic evolution. Modes of inheritance of phenotypes : Inheritance of phenotypes follows various pathways. Maynard-Smith 23 categorized the existence of two inheritance systems, classical DNA sequence dependent inheritance system and Epigenetic Inheritance System (EIS). Jablonka24 and Jablonka and Lamb 25 identified at least three different kinds of EISs, which help in the origin of new individuality. Misra et al. 26 listed nine types of inheritance systems, 203 which are categorized under four subsystems viz., genomic DNA of sex cells, genomic RNA, extra nuclear DNA and protein. They proposed that all types of inheritance are interconnected with each other and form an inheritance web. Recently, it is thought that evolution may show chimeric history 27. This may happen as a result of inheritance web. In addition to genetic inheritance, involving the duplication of genetic material and its segregation during meiosis, there are other hereditary elements that pass into the germ cells also. These include methylation patterns in DNA and chromatin marks, both of which regulate the activity of genes. These are considered “Lamarckian” in the sense that they are responsive to environmental stimuli and can differentially affect gene expression adaptively, with phenotypic results that can persist for many generations in certain organisms 25. Evolution of new level of individuality, mainly evolutionary transition from unicellularity to multicellularity, were assisted through EIS where adaptive characters are acquired in one generation and subsequently transmitted to next 24. Lachmann and Jablonka 28 also argued in favour of the existence of ‘Lamarckian’ factor in evolution of heritable phenotypic variation. Transmission of information through sex cell DNA follows Mendelian pathways under the screening of natural selection, while information transfer through other routes may escape Mendelian principle 26. It was argued by the authors that Weismann barrier is not always applicable and there are instances where such barrier is truly breached. Evolution of sexuality has given way to the proposition of Mendel’s law and the reliance on inheritance of acquired character has pushed to background. Recent studies on horizontal gene transfer entail that microorganisms have the adequate capacity to actively alter genomes in response to environmental stress or opportunities. It is quite obvious that horizontal gene transfer/exchange might be the dominant force in earlier phase of evolution and was more Lamarckian in character, and only the latter stages becoming more Darwinian 26, 29. Recently, Jablonka and Lamb 30 argued that heredity transmit in four dimensions i.e. genetic inheritance, the conventionally recognized mode of inheritance via transmission of DNA; epigenetic inheritance, or transmission of non-genetic information from parental cells to daughter cells, as in the cytoplasm of an egg; behavioral inheritance, or cultural transmission of learned traits; and symbolic transmission of information by means of abstract representation, especially language in humans. The authors 204 explained that the outcome of these modes of inheritance is subjected to the approval of natural selection. Their argument on evolution portray on four dimensions, corresponding to the four dimensions of inheritance. Evolutionary novelties and Evo Devo concept : One question is yet to respond that ‘why is there so much elaboration of somatic system’ if the somatic tissue has no role in inheritance. In nature, somatic tissues face most of the environmental hazards yet their role in inheritance is under scrutiny. All mutations/changes either in the germ cell or in the soma are the outcome of environmental stress i.e. through energy involvement. Long ago it was argued that all changes (mutational modifications) require developmental clearance [internal selection of Whyte 31 and epigenetic subsystem of evolution by Waddington 32 ] before expression and subsequent attestation from the nature (natural selection). The conception of embryonic development as a highly integrated series of canalized pathways owes much to Waddington’s development of the concepts of canalization, chreods, epigenetics, and the epigenotype. The integrated, heritable, epigenetic organization of embryonic development is Waddington’s lasting legacy to development33. Waddington demonstrated that how organisms respond to environmental changes with hidden genetic variations and integrated environmental responsiveness culminating into heritable change in response to selection, coupled development, environment, and evolution 33. Evolutionary process demands explanations of the underlying mechanism of the emergence of evolutionary novelties i.e. origin of entirely new morphological structures, new physiological functions, behavioural patterns, etc. Evolutionary novelties arise in organismal, functional, and molecular levels in relation to ecological shifts, stress, developmental pattern and other environmental factors 34. West-Eberhard 35 has noted that mutationally induced novelties would occur in only a family of individuals; whereas environmentally induced novelties would occur to a population. Moreover, the inducing environment would most likely also be a selecting environment. Thus, there would be selection immediately for this trait, and the trait would be continuously induced. It is argud that this type of evolution would indicate that the phenotype is produced first and then would later be “fixed” by the genotype 35. The author is of the opinion that genetic assimilation of morphs originally produced through developmental plasticity may result in the origin of new species. The author contradicted the long standing notion of mutational novelties have superior evolutionary SCIENCE AND CULTURE, MAY-JUNE, 2011 potentialities and argued that environmentally initiated and modulated novelties may have greater evolutionary potentialities than mutionally induced phenotypes 36. The concept of modern evolutionary developmental biology (Evo Devo) is concerned with the studies on the mechanisms responsible for major morphological changes and origin of homology. Extreme environments are closely associated with phenotypic evolution. Badyaev 37 approved the importance of stress-induced variation in evolution. He explained that ‘accumulation of phenotypically neutral genetic variance by developmental systems and phenotypic accommodation of stress-induced effects, together with the inheritance of stress-induced modifications; ensure the evolutionary persistence of stress–response strategies that provide a link between individual adaptability and evolutionary adaptation’ 37. Molecular biology, gene, DNA, etc. was not known to Lamarck. Still he felt the importance of environmental stress and its responsiveness in the animal’s body, physiological excitation, to the stimulation of growth that results into gradual transformation of characters. Lamarck had the distinct vision about the evolution, which ascertain through chain of causations. A proposition : A compile version of Lamarck’s vision with modern propositions on evolution can be explained as follows (Fig. 2). A phenotype (P1) in initial environment (E1) may exhibit phenotypic change (P2) in different environmental stress (E2). The continued environmental stress may induce genome/gene duplication where internal environment of the body could select one trait out of four options available (as an outcome of genome/gene duplication), may be after n number of generations. The nature of internal selection is likely to be based on epigenetic interaction among the parts of the developing organism, i.e. in compliance to epigenotype, which is the relationship between genotype and phenotype. This is somewhat internal tinkering that explains relationship between variability and evolvability. Variability is defined as the tendency to vary, and the variability of a system describes its ability to generate selectable variation. Therefore, evolvability depends directly on variability and evolvability is the capacity of a system to evolve in response to selection 38 . The authors characterized epigenetics as a collection of physical interaction(s) between the products of developmental processes that alters their final form 38. Evolution progresses due to the Figure 2. A proposed version of evolutionary process compiling idea of Lamarck and modern concepts. Phenotype P1 expresses in environment E1. If the population was shifted to an altered environment E2, a new phenotype P2 may result in response to new altered environmental stress. If the organisms were returned back to their original environment E1, within few generations, the phenotype will exhibit the old phenotype P1 . Continuous strong environmental stress for n number of generations may induce gene duplication event. If gene duplication takes place, the development pathway has more options to select and approve one of the phenotypes arising out of the gene duplication event. This is some sort of ‘internal tinkering’. The internally selected genotype will be fixed for the phenotype P2 even after the stress is withdrawn. However, after n number of generation phenotype P2 will remain unaltered if the organisms were returned back to E1. E1 =Environment 1; E2= Environment 2; P 1 = Phenotype 1; P 2 = Phenotype 2 VOL. 77, NOS. 5–6 205 instability of the inherent structure present within the biological system and interaction with the environment. Thus the topology of evolutionary structure is helical corresponding to the fundamental form of the nature 39. Origin of more than one genotype (due to gene duplication) is the foundation of instability of the inherent structure of the organism and its interaction with the environment is the outcome of the evolution. Origin of new trait starts with following events: biochemical → physiological → anatomical. It is to be remembered that Lamarck envisaged about the chain of causations from needs to efforts, to physiological excitations, to the stimulation of growth and eventually to the production of structures. The genotype of the trait originated due to gene duplication could be retained in the population either by subfunctionalization or neofunctionalization of the altered genotype (Fig. 2). The phenotype would continue to express even if the stress is withdrawn. This phenomenon may be explained as ‘genetic assimilation’ for altered phenotype or ‘genetic accommodation’ for novel phenotype. Both are possible if genome duplication takes place. The altered phenotype explains microevolution and the novel phenotype is the example of macroevolution. Role of whole genome duplication in evolution was also explained 40. J. B. Lamarck never visualized the idea of biological diversity (horizontal diversity), which was nicely explained by Charles Darwin 41. However, Lamarck’s argument for microevolutionary change was based on transmutation of species in accordance with the environmental set up. He showed the different lines of origin of various major groups of animals; still he failed to conceive the idea of macroevolution that is, origin of higher categories. He had the concept of origin of new traits and extinction. Darwin filled the gap by explaining that origin of divergence is always associated with both retention of traits and extinction (i.e. both horizontal and vertical evolution) 41. Further studies on Lamarck’s paradigm will certainly throw new insight in the evolutionary mechanisms hitherto not explained. Acknowledgement The author is thankful to Dr. Madhumita Manna, Head of the Department of Zoology, and to the Principal, Bethune college, Kolkata for their help. The author wishes to thank Kankadeb Mishra, Department of Genetics and Pathology, Uppsala University, Sweden for his help in preparing the manuscript. 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