By Marilynn Stark
Theory of evolutionary origin of eukaryotes: speculates that a bacterium could have invested its life within the cell of an archaeal host which resulted in a symbiotic relationship between them and had produced the first nucleus in cells in the sense of the evolutionary history of life. This symbiosis was to have given rise to the eukaryotes.
See also: a deeper discussion of theory of endosymbiosis which discusses how mitochondria and chloroplasts were likely to have evolved from endosymbiosis.
Art design: Marilynn Stark ©2007
Note: a more thorough discussion of the theory of the origin of eukaryotes is underway here. It begins with a review first of the concept of evolution itself.
Evolution is a concept most dear to biology. In fact, the implications of evolution are so broad that the theory of evolution forms as much as a guiding conceptual platform for thinking in all of biological theory as well as discourse and research. The theory of evolution states that organisms trace their sources to pre-existing ancestors and that through changes in traits across generations this source in previous time can be discerned. These two fundamental postulates of evolution theory will be discussed herein: that of variation wherein new traits arise and of heredity wherein the new traits can be yet conserved.
In the early 1800s the French naturalist Lamarck posited a theory of biological evolution. His idea that traits acquired within the lifetime of a single organism could be immediately passed on to its progeny also encompassed the idea of use: if an organ was used for survival's purpose, that organ would become in Lamarck's thinking altered due to its greater use. This change in form would then be inherited directly. The most famous example of this idea of the heritability of acquired traits states that the giraffe's long neck had been genetically created as the neck was elongated from stretching to eat leaves on trees ever higher; conversely, if an organ was to experience disuse in the lifetime of an individual, it would lose its genetic passage on to the next generation according to Lamarck. However, there was for Lamarck a profound rejection by the scientific community in his time since his scientific theories transgressed the prevailing theological idea that all of nature was a reflection of God's own design. The religious beliefs of mankind were yet to overshadow the growing evidence that life is not of constant feature; paleontologists, geologists, and natural scientists including the founder of plant morphology, Goethe, were uncovering and mulling over evidence that life varies greatly and also varies over great time. That species could change over time stood in contradistinction to the theologian's viewpoint that discrete acts of creation by God were the true cradle of life. Others in Lamarck's era were starting to see the light of a moving force in life which brought about changes across time. It is often stated that such possible evolutionary patterns had even been discerned by Aristotle himself.
The scientific intellect of man was destined to ultimately transcend the limitations of theological dogmatism which obstructed the understanding of biological science; with the work of Charles Darwin came a richer understanding of life, of the relationships of species one to the other, and of the conceptual fundament of evolution which unifies the multivariate characteristics of living beings in the sense of time. Time becomes the keel along which living things have coursed genetically so that changes in the characteristics of species are traced developmentally. In the case where that development actually constitutes the effect of time on living things in the much larger sense of time the concept of development becomes that of evolution; perhaps millions and billions of years may even be contemplated, and in the latter frame of reference do scientists consider the evolution of eukaryotes. Most importantly, biological evolution can be as slight as the change in a single allele of a gene, or it can be as great as the rise of a new species. What is properly called biological evolution must be considered not as a change passed on immediately in time; rather, any change worthy of evolutionary status biologically must concern populations of organisms whose passage for such change is via their genetic machinery. When researchers study the nature of mutation and how it occurs in an organism in the local sense in vitro or also in vivo results from those studies can be successfully extended conceptually so as to draw conclusions at the level of evolutionary thinking. This does not mean that evolution can be regarded as a spontaneous event although changes of ultimate evolutionary stature do arise out of certain genetic mutations which might be spontaneous in occurrence. A careful definition of evolution is also requisite to the current day matters which still invest themselves to some extent in the same theological resistances to science which obtained in the time when mankind was discovering biological evolution and its mode or modes. What exactly could be its underlying mechanisms? Please consider the following definition of evolution as rendered by a respected evolutionary biologist, Futuyma:
Darwin in 1859 published his influential work On the Origin of Species. Therein he cited the process of natural selection as operative upon the destinies of species to survive and to procreate in a context of living which is limited by availability of food and impinged upon by rigors of the physical environment as well as by its other inhabitants. Certain traits which have their own potentially labile genetic basis will lend a more probable survival to a given species; therefore, such a given species will influence the gene population accordingly with a greater frequency of expression in that population. This process of selection of certain gene types selects out those who can survive to procreate and thus pass on their genetic heritage; evolution, Darwin theorized, must occur as according to such a selective process in the biological sense of survival in a world of strife. Living things will naturally countenance strife due to environmental rigors and competition for both the food to survive and the cradle to procreate.
The concept of evolution can be expressed in the context of developmental biology wherein development of a single creature is undertaken for study. Ontogeny recapitulates phylogeny summarizes the biological theory that all of time for its effects on the genetic heritance of an individual species and therefore on individual members of that species is visibly expressed at the embryonic level. Ontogeny studies in particular how an individual originates and grows developmentally from ovum to embryo to adult. Phylogeny, tracing the evolutionary history of a species, must repeat as the entire biogenetic history as the embryo grows. This repetition of the broader genetic history of a species in the early stages of growth and development of its members was first stated by Ernst Haeckel in 1866, and it as such attempts to trace the history of the evolution of the human species through comparing it to other species for visible similarities. Haeckel exaggerated his observations of the similarities he observed at various embryonic stages when he proclaimed that an embryonic stage was the actual equivalent of the adult stage of its matching ancestor; for example, what are known as pharyngeal arches 1 were called gill slits by Haeckel. These gill slits were used by Haeckel to classify that morphological stage as the actual equivalent of the adult fish ancestor from which all species, including humans, would derive; thus did Haeckel per such examples substantiate the theory of evolution. Please see the picture here below of Haeckel's drawings in support of his biological concept of the law of recapitulation. Haeckel's concept of the law of recapitulation has been refuted since the early 1900s.
Haeckel's chart depicting embryonic stages for their correspondence to adult forms of such species as fish, turtle, rabbit, etc.
"I established the opposite view, that this history of the embryo (ontogeny) must be completed by a second, equally valuable, and closely connected branch of thought - the history of race (phylogeny). Both of these branches of evolutionary science, are, in my opinion, in the closest causal connection; this arises from the reciprocal action of the laws of heredity and adaptation... 'ontogenesis is a brief and rapid recapitulation of phylogenesis, determined by the physiological functions of heredity (generation) and adaptation (maintenance).'"Haeckel, E. 1899. Riddle of the Universe at the Close of the Nineteenth Century
The one-to-one mapping of phylogeny to ontogeny in a causal sense is not a standing truth in current day considerations by experimental morphologists and biologists. Modern biologists, however, are seeking to better understand how ontogeny and phylogeny are indeed connected although the absolute version of the law of recapitulation is untenable and no longer accepted. Haeckel had attempted in his derivation of the law of recapitulation to equate with embryonic stages a functionally active ancestral form, and this is not acceptable as valid. Indeed, one today observes that structural forms do repeat in embryonic development. For example, whales are mammals in an evolutionary sense, and they have undergone the loss of structure while evolving: they have lost legs, yet retain leg bones both as tiny remnants in adult form and at an embryonic stage when such remnants of legs first appear and then recede.
In the time of Darwin, during the 1850s, Gregory Mendel was conducting experiments with differing varieties of peas and proving through his mathematically posed data that traits were carried invisibly through generations. These recessive traits, he reasoned, since they would become visible again down the line of generations must hold the key to the diversity of life somehow. Mendel even sent to Darwin a manuscript of one of his experiments, and Darwin ignored it. Mendel gave up on his work in his own lifetime during the 1860s and died without any recognition for his contribution to science: the science of genetics. Almost a century later in 1953 the evolutionary theory whose mechanism is natural selection was to become substantiated as such when Watson and Crick solved the mystery of how life is passed on from generation to generation: through what molecule could information be transmitted heritably? Watson and Crick solved this, the question of the nature of the gene, by figuring out the structure of the molecule known as DNA, deoxyribonucleic acid. The function of DNA had been successfully seen empirically; when its structure could be postulated so as to match how genes could be coded at the molecular level, one of the greatest breakthroughs in the history of biology had occurred. With this newly found knowledge of DNA as the molecular vehicle of genetic changes an entire door to evolutionary history of all of life had finally been opened. The truth of Darwin's theory of natural selection as the motive force behind the evolution of life came into the true light of knowledge to the extent that how organisms experience changes in characteristics from generation to generation could be traced to the molecular source or expression of those changes; indeed, these invisibly transmitted changes could be traced now to the gene.
Aristotle studied organisms for their similarities in traits and their structural forms. His analytical method of grouping animals according to a system of traits contributed to the classification of living things. Verily, it is the classification of living things which constitutes the foundation of biological science. Taxonomy, whereby life's organisms are grouped and thus classified by similarities in physical characteristics, was furthered elaborately by Carolus Linnaeus. Linnaeus, an eighteenth century physician, botanist and zoologist who is called the father of modern taxonomy, developed the binomial nomenclature of classification. For example, Homo sapiens identifies the genus and species of man respectively. Simply by citing a species binomially so as to include its genus first is a shorthand implemented for its most recent commonality of ancestry with any other similar species. The levels or ranks of superkingdom, kingdom, phylum, class, order, family, genus and species comprise the fundamental sequence in the nomenclature for taxonomic classification. Man's taxonomic sequence can be listed as: eukaryota, metazoa, chordata, mammalia, primata, hominidae and Homo sapiens. Such a system of taxonomic classification allows organisms to be related one to the other by an approximate evolutionary distance. Organisms which share a close genetic ancestor in time have more ranks in common as well as more genes in common. Today, taxonomy also analyzes organisms using modern biological points of observation such as cell type and organization as well as biochemical and genetic similarities. When the wider question of the history of an organism's path through time in phyletic context is broached, then the inquiry pertains to the more expansive field of systematics. Systematics may concern how to figure out the evolutionary relationships of organisms by carefully tracing with new theories the actual mechanisms of evolutionary changes. Phylogenetic systematics may concern how the genes of living things both extant and extinct record the history of the relationships of those living things.
American Bullfrog (Rana catesbeiana)
Photo ©2007 M.Stark All rights reserved
Understanding the evolutionary relationships of life in its different forms is one of the most enterprising tasks in biological science, and the use of the genome in doing this task work has greatly enhanced the depth and relevance of all of biological inquiry to the meaning and presence of life on this planet. For instance, Darwin's theory of natural selection relates a population of organisms to environmental conditions. The Darwinian theory of evolution rests upon the fulcrum of such natural selection. The theory of natural selection predicts that those whose genetic makeup has undergone variation by some incidental mutations will by such mutations be made fit to survive and to procreate; those creatures will carry on a genetic line in an evolutionary sense. However, there can also be meaningful events which can select out only a given portion of an overall population. Change in the parent sampling from which is drawn the gene pool also creates genetic variation so that the power of mutation in forming new traits vital to survival would be much less central to evolutionary history in the development of a species, say, or an infraspecies rank. Such a phenomenon, known as the founder effect, is a form of genetic drift. When such an event as an isolate population brings about a change in the genetic traits of a species so isolated, then the parent sampling has effectively uprooted the purport in evolutionary thinking that natural selection is the entire motive force of the change in life across what is termed evolutionary time. If the scope of evolution is to include such vast time even beyond what fossils may tell of drastically different conditions on the Earth for life, then is natural selection perhaps not even predominant in determining the genetic paths of living things? Can the genome tell the history of the changes in life throughout eras of time if the proximities of genetic ancestors evade the selection of genetic traits but for changes in the presence of alleles only by founder effect proportions and not by natural selection alone? This brings up the questions relevant to the field of molecular phylogenetics wherein the actual macromolecular data of DNA and protein sequences become useful to the evolutionary biologist. It is theorized that if there is a great difference in the quantity of nucleotide sequence between a pair of genomes from different organisms, then there is also a very great distance in their ancestry in evolutionary time. Thus does the DNA become an historical document since like sequences, or homologies, in the coding of the genes in different organisms constitute what is regarded as an evolutionary relationship which is based upon the law of probability. Such a precise record of the changes in genetic code from organism to organism and across time as is afforded by the nucleotide sequencing of DNA lends new meaning to the record of life as the biologist views life: life as an entity which innately carries the capabilities not only to procreate from the genetic cellular function and thus replicate itself but also to express genetically through protein literacy as to genetic coding of the DNA and RNA. The genes comprise an information bank which is read by proteins through precise, signaled events at the molecular interstices of vital functioning, and this will result through subsequent events in gene expression. How the genomes of differing organisms relate to one another can be ultimately understood through in-depth analysis of protein activity, prospectively, and of RNA makeup. This macromolecular consideration will give a much more complete account of the meaning of species. Darwin had indeed used species as he formulated the starting point from which he was to derive his biological conceptualization. For this biological conceptualization, Darwin did rely upon morphological observations that aid in defining a species as a group of like organisms which can produce fertile offspring; however, what of the genetic characteristics of differing life forms as inferred from their macromolecular data? What would be, for instance, the gene expression of a living entity when it could be derived from the differences of a known fossil yet which had preceded that known fossil in evolutionary time? The morphology was once all-telling whereas now the innate chemistry might shed light upon the dynamic features of ancient living things as inferred from their genetic code. Will this inference match the geologist's mapping back in time as to the prevailing conditions on Earth and the kind of life it had supported? Such is the power of the discovery of the cache of information held within the once secret molecular data bank of the cell, the unit of life, whose replicating integrity when amplified unto the organismic level can now be studied across time of unreal proportions except to the most curious scientific pioneer that is the biologist.
Contemporaneously, there are many avenues of undertaking in biological research which have resulted from the progression of the knowledge base of the science of genetics since the momentous paper of Watson and Crick in the British journal Nature, A Structure for Deoxyribose Nucleic Acid and which is available here for your reading. June 26, 2000 marks the date when researchers exacted the very code of the entire human genome. This milestone in biological science offers a better understanding of human life. Exacting the code of the human genome might offer a way to improve our understanding of medical science and the question of longevity of the human individual. However, with this cache of information on the human genome arise certain questions of an ethical nature concerning the counterpart of such information as it might be imparted unto society in the wider sense: the question of stem cell research and how even human clones might be formed are leading concerns with which mankind is now presented. The entire science of biology, the study of life, has entered into a new context of how the information gained from advances in knowledge of genetics and particularly the human genome is to be interfaced with the society, indeed, with mankind as a whole. Bioethics is now a growing category of human endeavor. Once again, the religious precepts of man are invited into the conceptual arena for any practical impart of the knowledge and nowadays know-how of scientific research and results; biology in particular of all of the sciences and especially the branch genetics carry such social conscience to the ethical and ultimately political stump. Therefore, it is a most fascinating question to consider the actual veracity of biological evolution in the light of religious thinkers. One category of such religious thinking, that of creationism, rejects the very truth of evolution on theological grounds. This is indeed the same creationism which had obstructed Lamarck in the 1800s when he espoused a theory of evolution. In the view of creationism the world was created by God only and in discrete acts which transcend by the absolute nature of those acts the meaning of genetic descent as relevant to the human species. In the thinking of a creationist as according to the Bible it is absurd and invalid to maintain that all of life arose from particles and that through vast time landed in a clump called people. In consideration of the particular ideological basis of creationism for the formulation of ethical principles which are to be espoused for the betterment of society, then, the inquiry into the actual veracity of evolution on a scientific basis might be raised. Before beginning this consideration, however, it is important to honor the concept of biological evolution for its use in perceiving the complex and expansive, ever-changing world of life in the eye of the modern biologist. One key reminder might be invoked here: to understand the past of all of life through an unraveling of its evolutionary history might indeed seem trite when such is posed in the mind of one who is replete in thoughts only born of ardor for one's personal love for God. In such a contrast of ideation as the religious one which draws from the absolute, then, the defense of the nature of the world as resulting only from divinity's absolute power to create it, indeed, to have created it, will lend the marked proclivity to defend also from an absolute premise the concept that only God could create the world, and therefore all other considerations as to its history are not moot. Indeed, from this conceptual plane will arise the desire to look into the evidence for biological evolution and summarily refute it. On the other side of the argument is left the essence of biological science itself, which turns the clock of empirical knowledge so masterfully back in great time so as to study life in the broadest framework humanly possible on the behalf of gaining better insights into its mechanisms and its relationships in a cosmic sense to the universal plane of existence, even: what is the origin of life, an event of chemistry in a once-born universe? Therein lies that same sense of the absolute which the human mind ponders, wherein time becomes so much as next to infinite that chemical elements are placed upon the table of creation of life itself as the penultimate blocks from which was built life: it was just a certain combination of elements under the right conditions, perhaps?
Question: could there be infused into all of the arguments and counter-arguments regarding the origins of life and the validity of biological evolution a metaphysically-based outlook which also harmonizes with Divine principle and answers to the humanistic fears of the those who would render only unto God, and that -- a mightier hand than the ignorant, fumbling scientist could muster in the face of the unknown yet before mankind? Since the pioneer that is the scientist, whether evolutionary biologist or nuclear physicist, must certainly be reminded of the remarkable duty of conscience unto all for the good of all, it is only to be expected that the righteousness of the religious thinker and doer could serve for the good of all. Moreover, such a one as that must not hold a degree in science, or a chair as professor. It is this primordial fear which seems to be of paramount importance for the destiny of mankind, that no thinking individual, scientist or not, that no group of individuals, a consortium of scientists or a nation, can presume to take the reins of destiny from that one who had created it all by whatever name or scriptural writ, God? Can the refutation of the scientific basis for biological evolution be used so as to flatten the scientific community from playing the masterful game of altering life and controlling its destiny, seemingly, from an agility intellectually with equations and experiments which then map out into technological practicum? How much sympathy and compassion must be applied to the plight of the individual who ponders questions such as these, but has no answer. Can the faith which is rightfully held to quell this primordial fear over the sanctity of life itself ever be held in esteem high enough? What of the scientific experimenter who should be held to guidelines and rules of ethics in certain instances, as modern day science threatens the domain of life, now rendered as it is unto such as nuclear-level threat, experiment and also genetic alteration by human hands? Perhaps that scientific thinker will object to being constrained out of a line of experimental exploration on grounds which are not concrete. In compassionate consideration of contentions of such great magnitude as these the ongoing puzzle for inquiry remains as that of faith and reason, how they interconnect, and also with the inevitable decision as to what or who is right or wrong, indeed, in the best interests of all.
In light of the foregoing review of how the concept of biological evolution was posed, proven and has resulted now in the burgeoning field of genomics, the study of genes and their function, the question of the evolution of cells containing a nucleus, the eukaryotes, could have a deeper meaning. However, the discussion of the question of evolution of cells at the level of intricacy relevant to the slowly changing structure itself of cells will involve a much greater magnitude of evolutionary time. Moreover, this idea of the evolution of cells with membrane-bound nuclei would seem so radical to the pure thoughts of those whose religious beliefs would cause them to say that a biochemical view of the history of multicellular organisms, which includes humans, is refuted no matter what on the premise that human beings are God's most special creation. Such a theologically derived, absolutist way of regarding human life would further hold that a single act of creation had brought humans into existence, and therefore, no timetable matters as to the history of the human being whether single-celled life had once fully populated the planet or not. The questions being discussed as to the possible evolutionary origin of eukaryotes are presented in this vein of counterposing theological purport since they revert to the closest possible evidence of the origin of life itself for the biologist who traces prospectively via the genome. The genome of prokaryotes where prokaryotes are regarded as the putative predecessors of eukaryotes becomes as much as the map to the closest proximity of the actual beginning of life or of being from non-being; therein does the scientist seek how some primal set of chemical properties agglomerated could ever have become a self-replicating organism invested of activities towards its own sustenance. At this juncture of reversion in time to some possible beginning of life in the most abstract sense the biologist must surrender to cosmological precepts which purport the very beginning of the universe itself; from that birth of the planet come the geological processes which concern how life can be supported on this Earth. To study the genome for any first clue as to the origins of life becomes a hazy biological/biochemical idea in the much larger sense available now to science but through its other branches accordingly. Indeed, when Darwin across two decades of his life was preparing for his unveiling of the theory of evolution, he was affected by the geologists of his time. In the 1800s minds were dynamically opening to new tenets of scientific knowledge, and the geologists around Darwin were theorizing along with paleontologists regarding the evidence for a history of life on Earth which was much older than what the Bible indicated. Moreover, that life could be filled with changes was a new idea at the time. Indeed, both of these ideas were revolutionary in the time of Darwin; paleontologists were in his era discovering a certain fossil record of life which supported with concrete evidence this new regard for life as to its more ancient history and its nature to change over time. For example, in 1824 Rev. William Buckland, a professor of geology from Oxford, unearthed the remains of a Megalosaurus. The Megalosaurus had been named and described by Robert Plot in 1676 in his Natural History of Oxfordshire, a first. Over a hundred years later Buckland became the first to describe a dinosaur in a scientific journal, Transactions of the Geological Society.
This geological input through Darwin's intellect helped foment and solidify Darwin's intellectual conviction of the theory of evolution since the evidence was overwhelmingly in favor of the diversity of life as imaged through actual and undeniable fossils of living entities which occurred prospectively across a freshly conceived geologic time. Indeed, geological considerations now continue to involve the progress of our understanding of life for its origins as pertains to the simple readiness of the Earth for the support of life, and this is reflected in this quote herein from Iberall, a retired scholar from UCLA:
Although this discussion of the possible origin of life may continue to rankle the faith of one whose intellect is focused upon the absolute framework of life as from God's precept alone, the exploration of the beginnings of life on this planet standAlthough this discussion of the possible origin of life may continue to rankle the faith of one whose intellect is focused upon the absolute framework of life as from God's precept alone, the exploration of the beginnings of life on this planet stands to satisfy once again scientific man's curiosity to know the most regarding the living thing; if there is the power through nuclear fission to destroy life at great magnitudes physically, then any knowledge as to how life had originated can only help balance conceptually the power of the causation of its massive end by self-destruction. Such as the awesome
In summary, then, the destiny of mankind has seemingly inexorably fallenwithin a relative frame of reference into the force of man's scientific intellect and matching technological capabilities. With this fact in mind, let us attempt to decide upon the nature of biological evolution. To refute the very meaning metaphysically of evolution might also serve the selfsame human intellect which seems to have occupied the place of absolute power, a power which has historically and over long centuries been relegated reverentially to some idea of God. In addition, as we conduct such an inquiry, whether or not the exact religion is named, should not be moot. A metaphysical inquiry with its purview in the realm of the literal absolute might even still be likened to various kinds of religions since religious faith itself derives from the absolute as per the absolute nature of divinity. We will purport herein the more neutral metaphysical inquiry after the questions which pertain to biological evolution; however, first should we establish in the next section more of the history of the objective science of evolution and especially as it has worked synergistically with the progression of cell theory. The question posed here in the concrete scientific framework remains: the biological question remains as to whether or how multicellular organisms which are constitutively made up of eukaryotic cells actually arose in the sense of evolution from prokaryotic cells. This very question of the hierarchy of the cell, the functional unit of all life, as to its possibly increasing complexity through evolutionary time from unicellular prokaryotes to the eukaryotes requisite to complex multicellular life addresses the greatest range of biological truth. Such broad conceptual range regarding the power of evolution in the formation of life in more advanced forms leads to the consideration of how life might have evolved to form human life, as well. By discussing the metaphysical tenets of truth which can be mapped onto this greater range of time evolutionarily to the putative prototypic prokaryote is the reductionist view of life more completely addressed. The idea of life as a set of chemicals with the prefix "bio" as its handy addendum simply offends some whose faith in the sanctity of life is challenged fundamentally by such a totally analytical viewpoint of some quintessentially particulate entity -- life. Rather than to believe in a laboratory report by a few human scientists regarding early life forms at the cellular level, some of great heart for God would refer instead to a divine presence in the beauty, mystery, and even, indeed, the sacrosanctity of life.
Therefore, to juxtapose this question of the way eukaryotes had gained a nucleus, a membrane-bound nucleus, to the validity of biological evolution rather from a metaphysical viewpoint seems justified. Such a treatise as this juxtaposition entails may serve to pacify many whose intellects are disengaged from all of science because the rigors of questions such as evolution offend so deeply. For those who are offended by it, any rigorous objective findings concerning evolution may even tear apart the humanistic hold which should rightfully allow science to explore only with a concomitant humanistic eye if not more drastically with a humanistic shield. To the creationist a reductionist view of life, life as a matter of proving its biochemical mapping back in an evolutionary timescale, should better be rectified unto all that should be reduced instead to God. The strict creationist most likely will cite surrender to God as the theological concept which becomes the watchword relevant to any question regarding the nature of life and how man should not tamper with its destiny through willful acts. The advances in medicine for the treatment of disease which have been derived from biochemical research have tended to mollify, perhaps, the more absolutist school of creationist thought.
With this preface to the real biological inquiry at hand, there is an invitation for all whose beliefs are in science and whose beliefs are in God and/or truth to meld together their hopes for a greater common ground. If only some light can be shed upon the contentions which inevitably arise, when man takes the moment to form a matrix for decision through his scientific know-how upon matters of the destiny of life only because he had so brilliantly figured out its hidden course through vast time and from the cell on and up. The derivation of life through that vast time of evolutionary development and change only reckons fundamentally with the metaphysical idea of source: to know the essence of something is to find and understand its source, from whence it came.
We owe to Aristotle, probably the most towering intellect ever to rise in the Western heritage of faith and reason, the scientific method with which we practice scientific research today. Indeed, the biological branch of the sciences, instituted through his philosophical reference in thinking, had led the way historically for the unfolding of the other sciences. The utility of gaining empirical proof in scientific inquiry began essentially with the great Aristotle even though his scientific conclusions were not all proven subsequently, and especially was that the case in physics. The method of refutation, however, is the exact way of science to ferret out the truth in an ultimate way; what is refuted can be forgiven in an overall sense. As each question which stands to be refuted for its answer forms nevertheless the step to the next logical resting point of truth in results relevant to the stated inquiry or experiment, so does the process of attaining to empirical perfection ascend ever higher -- sequentially so. Indeed, the requirement that the existing scientific work on a topic should first be stated and then either refuted or substantiated by a next logical research or researcher is essentially the exact method propounded by Aristotle himself. Aristotle's philosophical inquiries and his scientific research in zoology worked together to make one the other more sound and satisfying to his intellect. Nature enlightened Aristotle. He skillfully set up a systematic way to classify animals while he drew up a metaphysical algorithm which would help explain the traits of the creatures. Aristotle envisioned a Great Chain of Being which coursed from non-being to being in an upwards hierarchy with man in the middle of the two. The minerals were at the bottom, then plants, and then animals in his model. These categories were part of a group which was classified as in the Realm of Becoming; then man, demons and angels ascended hierarchically unto God, all of whom were considered to be in the Realm of Being.
The Great Chain of Being of Aristotle
(Above paradigm credit to: UC Museum of Paleontology's Understanding Evolution)
Aristotle in his attempts to classify animals analyzed them as according to a metaphysical hierarchy of causes; there are four causes according to Aristotle: the final, the formal, the material, and the efficient. In the final cause inheres the sake for which a thing exists. In his purport of this final cause as it relates to the efficient cause lies an important insight which touches remarkably on a sense of evolution in Aristotle's biological analysis. Here is what Aristotle says regarding this idea of how to understand the characteristics of living things as they express in nature in Book V of On the Generation of Animals:
Aristotle made the distinction between a final and an efficient cause; this efficient cause has the power to work upon the material cause so as to bring about changes in the characteristics of a living thing. In so doing, he set up a way in which animals could be classified by the greatest grouping as according to more universally recognized traits which were held in the greatest degree of commonality among them; as certain traits might vary, yet were not of the metaphysical status hierarchically to group them as constitutive of a more universal set, such traits were placed in a lesser status, the status which would give leverage for variation as by cause seen as effect. In this sense, he says, " In fact in some cases this condition has no connexion with the essence of the animal's being, but we must refer the causes to the material and the motive principle or efficient cause, on the view that these things come into being by Necessity." The insight of Aristotle is even more astounding when he makes a distinction between becoming and being; this very distinction between becoming and being as delineated by Aristotle is how he set the intellectual framework for the discovery of evolution conceptually, and one can read into it Aristotle's perception of the fact that animals must have evolved. Let us say that a creature can take on a new trait is a given. The metaphysical point of Aristotle is made that the instance of variation in trait is part of the final cause only because the final cause exists as inherent in the creature; therefore, the variation in trait does not occur for the sake of the final cause since the final cause is for its own sake alone. Being is beyond becoming in this sense since any efficient cause is so because it is derived from the final cause more ultimately; becoming (such as an event of variation in the Darwinian sense) is dependent upon being (the evolutionary level of species), yet being is not dependent upon becoming. This conceptual framework of Aristotle might be subtle enough. However, if applied from the darkness of the exact nature of variation in living things in the centuries to come when science was progressing past the delimitations of Christian dogma, a middle ground had been conceptually plotted by Aristotle. Obviously, if speciation were to occur, the changes by trait which were to account for such speciation would have to be such that the individuation of the final cause would give way to the moment of some drastic efficiency upon a given species. Even so, the sanctity of life as translated through the purport of a final cause separates still that creature from its newly attained status as a new kind of species: yes, it came from the power of change in biological vector somehow. However, that new species remains even transcendent to the very changes that put it there? For one who sees only the design of God's creation because he must have created a non-changing world of nature as to its members, yes: the only change is one event, that of the creation. This is the middle ground which befriended Aristotle down the ages to the Christian theology. In reality, before evolution was actually discerned more minutely in scientific endeavor and past Aristotle's metaphysics one can argue that it would be impossible for a new species to arise without the force of variation upon the older or pre-existing one; therefore, evolution must certainly discount the final cause as being independent of the efficient cause. This is a cogent point, and herein lies the brilliance of Aristotle as a metaphysician: how to cross this seemingly paradoxical categorization as to cause is the question. Being for its own sake alone could allow no becoming to change it, yet becoming or development does depend upon such a being. Such a paradox only reflects the difference between the relative frame of reference and the absolute. In drawing upon this difference between the relative nature of change and the higher status of the nature of what simply is as that which just is Aristotle had set up a logical bridge not only between Christian dogma and free-thinking scientific man prospectively; he had also formed a biological hierarchy based upon the kind of change which occurs in nature among creatures so that the way to understanding how species might evolve had been pre-formed, so to speak, in the zoological work of Aristotle. To say that creatures exist for the sake of being is actually a reverence for nature. To further say that traits earn a status as to whether or not they define a given creature in a staid sense of classification so that certain variations in traits are only of the hierarchy of efficient cause, pre-forms the idea of natural selection which was to become the mechanism of Darwin's law of evolution. Again, these are subtle points which are difficult to grasp if one already is studied in the biological concepts relevant to the discussion of evolution, indeed, in science itself, now in its ripened form, but as drawn from the thinking of Aristotle which was hypostatic to the development of all of biology.
The paradox presented here as to the hierarchy of causes correlated to the level of variation in trait ends when the scientific thinker sees that in Aristotle's terminology the efficient cause has the power to bring about a new species. However, this in no way attenuates the place of the final cause if we conscribe to the philosophy of Aristotle. In presenting the absolute nature of being as a final cause and including this final cause in an understanding of the world of nature Aristotle set the question of species as to hierarchical level of traits apart from variations in characteristics of animals which were not totally defining of species per se. In so doing, Aristotle gave the world of nature and its creatures a status equivalent to the spiritual in a sense even though they were not in his Great Chain of Being part of the Realm of Being itself. Rather, they were of the Realm of Becoming and still unified with the Realm of Being through the final cause: everything exists for a final cause. Thus, says Aristotle, ". . . for the process of Becoming or development attends upon Being and is for the sake of Being, not vice versa." The Realm of Being is closer to the absolute, God, hierarchically. He spoke of the nature of existence for the creatures in terms of the final cause as it relates to them wherein he asserted the place of the absolute in the lives of living things. In this world of living things, Aristotle philosophized, there was a cause of such magnitude, the final cause, that its connection to other causes was universal and in a sense one-way. Since the final cause did not depend upon, say, the material cause, any change in the material world brought about by an efficient cause would not affect the final cause: this is a terminology which essentially says that the absolute is not affected by the relative. On the other hand, an efficient cause could affect a material thing, certainly, but would be of the status of dependent on the final cause; never could this efficient cause be independent of the final cause since the efficient cause should be part of the relative realm. The relative realm reflects becoming since it is the realm of change; the absolute does not depend on the relative even though the absolute realm also includes the relative realm. The absolute realm is sheer being. The relative realm is that in which things exist, yet they exist also in the absolute realm in the sense of dependency upon the absolute realm, and so they are said to exist: they take on the nature of the absolute only in so far as they exist for the sake of the absolute; and thus do they exist at all. 'And thus do they exist at all' means that they are dependent upon the absolute which is indifferent to things across time and across change.
One of Darwin's contemporaries was Wallace, who, like many others of that time, was in the same mind force of discerning such a momentous insight regarding the evolutionary history of life as was Darwin. For Darwin and Wallace the theory of evolution biologically speaking amounted in plain terms to seeing into the essential nature of life. In the introduction to On the Origin of Species Darwin says, "Until recently the great majority of naturalists believed that species were immutable productions, and had been separately created." In fact, Darwin himself cites three scientists who had propounded the radical idea of the origin of species in 1794-95: Goethe, Erasmus Darwin, his grandfather, and Geoffrey Saint Hilaire. In addition, he cites thirty-four authors who believed in the "modification of species," twenty-seven of whom had written in the fields of natural history or geology. By opening the empirical minds of the scientists of the 1800s to concepts of life which were of the relative realm and were far-reaching back in time the very concept of evolution was literally swinging the entire scientific world into a predisposition for even more revolutionary discoveries in biological science.
Indeed, the genetic inheritance of life was to be placed in line for further biological inquiry by the idea that a creature's genetic traits were far more than the result of two parents as progenitors in immediate time as a frame of reference. Lamarck had founded in 1801 his theoretical mechanistic basis for the theory of evolution with his theory of the inheritance of acquired characteristics, which was to be supported by Darwin. Indeed, Darwin referred to Lamarck's theory of evolution in this kind of light: "He (Lamarck) first did the eminent service of arousing attention to the probability of all changes in the organic, as well as in the inorganic world, as being the result of law, and not of miraculous interposition." (On the Origin of Species.) Darwin espoused the theory of pangenesis so as to account for a mechanism that would allow traits to be invested in the genetic mode of inheritance from one generation to the next. Accordingly, Darwin's theory of pangenesis allowed that certain gemmules exist in somatic cells, having the capability to pervade the reproductive organs. Upon reproduction, then, the traits of the wider body which had been exaggerated with use in the Lamarckian sense would be passed on through the germ cells. Therefore, the use/disuse of Lamarck as a source for variation in genetic lineages was supported theoretically by Darwin's theory of pangenesis. However, Darwin asseverated that the power of variation in characteristics as derived from a pangenetic basis would be far too weak to have brought about the structural perfection in creatures which matched the elaborate function they exhibited in order to achieve a successful, surviving life. He could not imagine that such mere external conditions could have caused the formation of the structure itself of species. Also, the actual creation of a species became a relevant scientific concept for the thinkers of Darwin's time since paleontologists were discovering fossils of extinct species.
Darwin in deriving the mechanism of natural selection in order to account for how living things evolved had originally been greatly affected by a certain writing of 1798 by Malthus titled, "Essay on the Principle of Population." This essay provided a highly theoretical basis rather from an economist's point of view for the place of population, in this case the human population, to survive but for the struggle for an arithmetically modulated increase in means of sustenance whilst population could increase geometrically. This concept for Darwin of population growth interjected into the question of survival for organisms in the most generic sense took Darwin conceptually to the fore of his theory that living things could be considered as populations whose probability for survival could be somehow derived from those populations. Thus was Darwin's theoretical thinking directed away from the immediacy of the inheritance of traits as had been set forth by Lamarck. Rather, if populations of living beings were to undergo changes, then natural selection of those who survived and procreated would promote the changes in traits across generations together. Then, among those populations which had accrued changes over generations, Darwin reasoned, there could arise the chance for a new species to occur over a much longer time.
1Pharyngeal arches, also called branchial arches, gill arches or visceral arches, are seen in the embryonic development of vertebrates, and they arise from the neural crest. They arise in the fourth and fifth week and are thus useful in establishing the stage of an embryo. These arches are comprised of mesodermal tissue, beginning as one ridge-like arch which separates the mouth pit from the pericardium. As development continues, a total of six arches are to form in a non-sequential manner, and the fifth arch topologically also disappears in humans alone. The first three arches are to contribute to the structural region above the pharynx, and the others are to contribute to the larynx and the trachea. Please see these diagrams from Gray's Anatomy here below. Click onto the thumbnails for larger pictures:
Please note: It is understood that the material from Gray's Anatomy of the Human Body is now in the public domain,since its copyright has expired (Copyright of 1918.)
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