Darwin’s theory of evolution was one of the greatest scientific thoughts in human history. At the core of the revolutionary premise is natural selection, which is a process that takes place over successive generations and is attributed to variance in genotype reproduction. Its basic understanding is that it requires heritable variations in a specific attribute. The process equally requires differential survival based on adaptation and reproduction of the subsequent trait. Therefore, the rationale is that natural selection is limited by a population’s existing traits or genetic variations. Species adapt to survive, but the process does not support the assertion that natural selection produces a perfect organism. Natural selection is constrained by linkage disequilibrium, which is when allies proximate to the chromosome are inherited at greater frequencies. It cannot create a new perfect organism because a species’ existing genetic variance constrains the process of evolution.
Natural selection is the primary force in Darwinian evolution theory and can generate populations through adaptation and reproduction. According to Godfrey-Smith, without differences in traits, such as organism fitness levels, adaptation to an environment cannot take place (42). The philosopher’s use of fitness explains how organisms adapt to survive and thrive in particular environments. The concept of adaptation illustrates that natural selection and evolution as a whole cannot create an organism from scratch. The physical propinquity of alleles determines the immediacy of evolutionary benefits prescribed to a polymorphic population. For instance, the factors that allowed crocodiles to evolve and become land animals are different from those assigned fish to the seas. Orr, in his article, asserts the evolutionary concept of fitness entails the ability of organisms to survive and reproduce in the environment they find themselves (531). Adaptation is not the only reason for cancelling out the argument of novel biological forms.
Natural selection is a process that affects individual phenotypes and not alleles. How it functions is another limitation reinforcing how it cannot produce perfect organisms. During inheritance, some alleles may be more prone to be passed on together with those with a beneficial phenotype because of their proximity to chromosomes (Mergeay and Santamaria 104). Alleles that are inherited together represent what is considered as linkage disequilibrium. For example, when a neutral allele is connected to a beneficial allele, it has a selective advantage. The transfer frequency of the allele increases because of genetic hitchhiking. Therefore, any individual or organism could be carrying beneficial, neutral, and unfavourable alleles. The presence of neutral and unfavourable genes counters the argument for perfect organisms. Natural selection can result in the loss of good alleles if an individual has an overwhelming amount of bad alleles hitchhiking.
Polymorphism is another factor that limits it from creating perfect biological forms. In polymorphic relationships, one morph might assign a species a higher fitness level compared to another, but it might not increase its frequency due to intermediate morphs (Thomas 15). Fitness is a useful concept because it bundles together all the factors that are essential to natural selection, namely reproduction, survival, and mate finding into a single notion. Consider a hypothetical scenario of white and black-coated rabbits living in the desert. The white rabbits blend with the sand while the black ones blend with the rocks. Given the black rabbits are fitter, the principles of natural selection outline the population of white rabbits will decrease over time. However, an intermediate trait of brown rabbits cannot blend with either environment. Therefore, the population of black rabbits might equally not increase because the intermediate morph is vulnerable to predators. Disruptive selection shows another instance of why natural selection cannot breed perfect organisms.
The different mechanisms associated with natural selection can explain the clumpiness of biological diversity. Important to note is that not all evolution is adaptive (Mergeay and Santamaria 106). The conventional approach of the process involves the assortment of the fittest individuals and will often result in a more robust population. However, as discussed in the preceding paragraphs, other forces of evolution, such as genetic drift, disruptive selection, and gene flow, can counter the effect of conventional natural selection by introducing harmful alleles to a population. Adaptation can equally result in the loss of good genes. Evolution has no pre-conditioned direction or purpose. The process does not transform a population into a preconceived ideal, resulting in ‘clumpy’ biodiversity. Natural selection, from a broader perspective, is the total of all the forces influencing phenotypic variance. There is also the argument of competition increasing biological diversity.
Natural selection as a biological process entails developing certain features or characteristics that allow an organism to adapt. The outcome of the change process is a natural property that interplays with other factors in the larger biological function. Godfrey Smith fails to provide an accurate hypothesis regarding natural selection because he does not consider all the forces affecting phenotypic variance, including the different mechanisms for gene selection. There are different ways for organisms to survive, resulting in regular space clumps of the same species within a particular environment. Nevertheless, there are reasons why there are controversies regarding evolution. Science still does not have comprehensive experimental studies for genetic mapping and characterization of adaptive phenotypes. The controversies highlight aspects of experimental and conceptual biology and philosophy that are yet to have conclusive answers. Regardless of the gaps, what is known as natural selection focuses on increasing an organism’s ability to adapt and survive.
Godfrey-Smith, Peter. Darwinian Populations and Natural Selection. Oxford University Press, 2009.
Mergeay, Joachim, and Luis Santamaria. “Evolution and Biodiversity: the Evolutionary Basis of Biodiversity and Its Potential for Adaptation to Global Change.” Evolutionary Applications, vol. 5, no. 2 (2012): 103-6. doi:10.1111/j.1752-4571.2011.00232.x
Orr, H Allen. “Fitness and its role in evolutionary genetics.” Nature Reviews. Genetics vol. 10, no. 8, 2009, 531-539. doi:10.1038/nrg2603
Thomas, Paul. The Gene Ontology and the Meaning of Biological Function, In The Gene Ontology Handbook. Springer, 2017.