Theories of Evolution - Term Paper Example

Why Evolution Is True Why Evolution Is True There are many theories that which have been put forward to explain the origins of life. However, the theory that has received a lot of attention is the evolution theory. While some people dispute it, others seem to agree with the theory. Coyne in his book Why Evolution is true attempts to convince people into believing in evolution (Coyne, 2009). This paper provides a critical reflection on every chapter of the book in an attempt to get deeper understanding of evolution. Chapter 1: What is Evolution? This is the introductory part of the book. In my view, the book covers key suggestions of evolution theory. This is unlike many treatments of evolution where readers are often confused as a result of being conflated with different definitions of the term. The decision to divide “Darwinism” into six components makes the understanding of various concepts easy (Coyne, 2009). It is indeed true that, over time, allele rate of recurrence change in an inhabitants. It is also true that different organisms have occupied the earth at different times. The critical role of natural selection is in this is also an undisputed fact. Common ancestry is received positively by a majority within the scientific field (Coyne, 2009). My reflection on common descent is that while it is a defensible position, it is not as much supported as it is made out. Consequently, the points of concern in this chapter, in my view, include the extent to which gradualism is true and the sufficiency of natural selection. Chapter 2: Written in the Rocks The second chapter of the book is ‘written in the rocks.’ It uses fossil evidence to justify common descent. It is indeed true that fossil records show a tendency where simpler organisms precede more complex ones. This is also exactly what one would anticipate as a result of a common origin (Coyne, 2009). A feature that would be absent in Darwin’s theory, but would be the noticeable pattern of morphological difference preceding diversity (Coyne, 2009). In my view, an interesting aspect of the fossil record is that, unlike Darwin’s theory, it ranks the higher taxonomic categories first and, consequently makes them appear first in the taxonomic ranking. There are three main evolutionary transition trends specified by the fossil record i.e. fish to amphibians evolution, reptiles to birds and whales to terrestrial mammals evolution (Coyne, 2009). Accordingly, there are three important insights that emerge from the fossil record. Firstly is that the fossil spells out the evolution process (Coyne, 2009). The records within rocks provide a great deal of confirmation on the part of evolution theory. The other lesson is that transitional forms often occur in the fossil record in the exact manner that they should. For instance, after the dinosaurs, the earliest birds occurred, and the modern birds followed this (Coyne, 2009). It is essential, however, to mention that this sequence does not always hold as “out of sequence” fossils have been found routinely. Another essential lesson from the fossil record is that an evolutionary change, irrespective of the magnitude, will always involve the old being remodelled into new as exemplified in convergent evolution. Chapter 3: Remnants-Vestiges, Embryos, and bad Design This chapter commits itself to the argument of “evolution-of-gaps” fallacy which, retreats with modern scientific models trying to point out reasons for designing the features. The features include the following: Vestiges: Some of the vestiges alluded in this chapter include the wings of the ostriches and other non-flying birds, for example, the ratites. Some people argue that the ancestors of the ostrich must have been flying birds; there is no compelling evidence to support the assertion. My thoughts are that this chapter is trying to demonstrate that modern evolutionary theory is sufficient to explain the gain of new functions. Another example given is the vestigial hind limb and pelvis bones in whales. There could a very high possibility of whales possessing hind limbs at some stage in their evolution history; however, this shows loss of traits as opposed to their origination. Other exhibits include the human appendix and the vestigial tailbone (Coyne, 2009). Dead Genes: Attention is also focused on pseudogenes. Under normal circumstances, one could anticipate to get genomes of numerous species “dead” or “silenced” genes i.e. those that were quite useful at some point, but are not expressed now. Contrary to this, the assertion that all species came from scratch only suggests that no such genes would be in existence. The reasoning behind this argument is that there would be no common ancestry. Examples of pseudogenes include the human olfactory receptor (OR) and the GULO gene in plants. Although the chapter views OR as non-functional, it is not certainly the case (Coyne, 2009). Bad Design: The argument surrounding suboptimal design is, in my view, not correct. This is because a closer examination of the cases formerly thought of as “bad design” turns out to show design trade-offs. The argument continues having a series of lapses as the understanding of these systems get better. Some of the designs the chapter alludes to as “worst” designs include the Recurrent Laryngeal Nerve (RLN). Whilst the author terms it as a worst design, studies suggest that there are a number of good reasons for RLN’s chosen route (Coyne, 2009). Palimpsests in Embryos: This chapter purports that the developmental stage of all vertebrates is the same. In my view, this is not an outright truth. Normally, the developmental stages would differ significantly at early stages; converge mid-way through development, and then diverge later in development. This is also accurate of gene manifestation patterns (Coyne, 2009). Chapter 4: The Geography of Life This chapter focuses on evolutionary biogeography, a field that tries to link global distribution of organisms to aspects such as migration and occurrences, for example, continental drift among others. Accordingly, the chapter supports its assertion with various examples such as the marsupial mammal concentration in South America and Australia. Also, fossils of marsupials have previously been established in America. The argument here is that Australia and South America were initially joined by a continental land bridge, now Antarctica. It follows, therefore, that for evolution to be factual there should be indication for marsupial relocation from America through Antarctica to Australia. Studies have suggested that indeed there is evidence of such a migration and thus validates the claim. The effectiveness of this argument in trying to establish a common descent, in my opinion, is in serious doubt. For one, there are many cases of organism distribution that do not quite conform to the explanation by common descent. For instance, fresh water crabs distribution around the world. One fact about crabs is their inability to survive in salt water for long periods. According to Molecular and fossil data, a divergence occurred long after the continental break. Surprisingly, freshwater crabs can be traced in distantly apart regions such as India, South Europe and Africa just to mention a few. In a nutshell, while evolutionary biogeography demonstrates a limited common ancestry together with speciation, the mentioned biogeographic anomalies undercut the force of this argument. Chapter 5: The Engine of Evolution This chapter, unlike others, attempts to show that the causal power of the proposed mechanisms lead to changes in evolution, a point that contradicts the origins debate. The author dispels Darwin’s notion in The Origin by bringing a new dimension to natural selection. While natural selection is more like a designer substitute, Coyne dwells on expounding how different processes work in nature. In particular, the chapter gives useful insights on random mutation, gene mutation, genetic drift and Darwin’s idea of natural selection (Coyne, 2009). Genetic drift concept is presented as being powerful to natural selection. Following insights on a number of evolutionary processes, the author focuses on the evolutionary processes that occur in the laboratory. In particular, the author explains various experiments conducted in the laboratory, and that reveal the continuity of the modern evolutionary processes. The best example to demonstrate modern evolutionary processes is the resistance to drugs and poisons by micro-organisms. Bacteria such as Staphylococcus aureus no longer respond to many antibiotics for instance penicillin and methicillin. In addition, the chapter cites DDT resistance in insects in its quest to show just how much evolutionary mechanisms are capable of achieving. It is useful to mention here that resistant mutants are often rendered less fit more than the “wild type.” According to the chapter, one realizes the author does not address any of the challenges that the evolutionary processes are supposed to accomplish; for instance, the issue of irreducibly complex systems in the bacterial flagellum. Chapter 6: How Sex Drives Evolution This section of the book attempts to answer pertinent issues on sexual selection and the benefits accrued from evolutionary sex. It commences with the evolutionary costs of sex and depicts males as being the underprivileged sex compared to the female sex. A comparison with the a-sexually reproducing species show that they often reproduce at a faster rate, about twice as much as the sexually reproducing species; consequently, the asexual species outdo the sexually reproducing species. Another significant point is the perpetuation rate of the offspring’s. Usually, the sexually reproducing female species will successfully perpetuate nearly half of their genotype. Following the fact that the underlying reason for natural selection is to ensure that those organisms pass on their successful genes survive, sex then remains right at the center of evolution. While the author gives various benefits and downfalls of evolutionary cost of sex, my views are that he fails to account for how sexual reproduction came into being. It should also be noted that the genetic flexibility only benefits the future generations as opposed to the current. In my view, the main undoing of natural selection is that it lacks foresight and, as such, fails to retain biological phenomena for their use in the future. One also wonders how sexual reproduction could evolve by mutation as to be fixed by virtue of some organisms surviving the said disadvantages. Another view relating to the role of sex in driving evolution relates to the fact that gametes undergo meiosis and mitosis forms of cell division. Usually for sexual reproduction to be a success, the meiotic process evolves to half the chromosome number in the gametes and not in the body cells. Chapter 7: Origin of the Species This chapter focuses on the origin of the species (Coyne, 2009). The chapter, in my opinion, is carefully thought and would agree with most of the assertions made. In a nutshell, speciation is real (and understood) process for which there is overwhelming evidence (Coyne, 2009). Chapter 8: What about Us? This chapter focuses solely on human beings. It attempts to give an evolution account of the human race citing alleged human-chimpanzee intermediates such as Sahelanthropus tchadensis and Australopithecus africanus (Coyne, 2009). In the chapter, the author uses phylogenetic inference based purely on both cranial evidence and dental evidence. Although cranial and dental evidence is often used in producing a phylogenetic hypothesis regarding human beings and their fossil relatives, it remains to be seen whether this hypothesis holds upon being subjected to external validation. Studies have shown that phylogenetic hypothesis based on cranial and dental data is incompatible with molecular phylogenies; as such, phylogenetic hypothesis on human evolution cannot be relied (Coyne, 2009). Also, the time gap existing between Australopithecus afarensis and Homo erectus leaves a lot to be desired. Following a short time that creates the difference between the two species; one wonders just how evolutionary mechanism could work so fast to accomplish the change from Australopithecus afarensis to Homo erectus (Coyne, 2009). In my view, such a change could not be possible within such a short span of time. Chapter 9: Evolution Redux In this chapter, the author tries to psychoanalyse the critics of evolution saying the reason behind their scepticism emanates from their religious commitment (Coyne, 2009). This psychoanalysis, in my view, is ironical considering that it is a materialist who is more concerned with the evolution of life as opposed to the theist. In conclusion, my view is that the arguments presented for common ancestry are not satisfactory. Although some arguments carry more weight than others, the author fails to address many arguments opposing common descent. While many people criticize Darwinian evolutionary theory, the bone of contention is not based on theology, but rather that the assertions put forward by modern evolutionary theory fail to conform to the evidence. Reference Jerry A. Coyne, (2009). Why Evolution is True. New York, NY: Viking Publications Read More