Lewontin on quasi independence

Definition of quasi independence

In an attempt to understand the process of evolution, Richard Lewontin explained that adaptation is a necessary prerequisite to occurrence of evolution. However, he also believed that it can be workable when the reproductive ability of the organisms and the phenotype of the concerned subject had two particular traits: quasi independence and continuity. Continuity meant that minor changes in traits only affected minor ecological processes; this meant that reproductive fitness could also be marginally affected.

Conversely, quasi independence refers to the fact that there a number of pathways that can lead to change in an organism. Some of these pathways can either lead to negative effects or positive effects on other organs and ecological processes of the subject. However, the negative effects of the adaptation are not powerful enough to overcome the fitness increments created by the adaptation (Levins and Lewontin 79).

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Why Lewontin needed the concept

An example of quasi independence is a series of mutations that occur in the body of a zebra so as to change the length of its bones. This change in the physical appearance of the zebra will only lead to adaptation if it has been shown that the zebra’s major threat to survival is the need for speed. If other ecological needs are prevalent, then the change in length of the leg bones will be of no evolutionary relevance. For instance, if a certain predator uses tactical methods to attack the zebra, then the change will not be useful to its survival.

Second, it will lead to adaptation if an alteration in speed will not lead to other complications in the organism’s ability to adapt to its environment such as greater metabolism or need for more food. This increased need for food in an environment with limited resources will offset the positive benefits that emanate from the escape of the zebra from its predators. Third, if the lengthening of the zebra’s bones does not create a negative effect on other parts of the body.

The organs need to be able to function in the same way that they did prior to occurrence of the mutation. Longer bones would require greater energy during the developmental process. They would also be more prone to breakage, or could lead to other morphological challenges in the rest of the body. As a result, a change in a certain characteristic would only be relevant to evolution if the net effect of the trait on the whole organism was positive.

Lewontin needed quasi independence in order to explain why certain adaptations were evolutionarily significant or not. He needed to place mutation in context such that it would be possible to assess its relative usefulness. Quasi independence allows one to understand what leads to net reproductive fitness with regard to the characteristics that arise in organisms.

Whether the theory fits in with Lewontin’s overall view of the evolutionary process

Lewontin asserted that organisms existed as integrated wholes rather than products of atomic traits. He believed that if too much emphasis was given to the genes that led to the development of a certain trait, then the organism would be placed at the end point of the evolution process, yet this was not a wise thing to do (Levins and Lewontin 80).

He argued that if a seedling was small, it did not matter whether a small seed (hence the genes) led to the prevalence of a small seedling or whether the lack of sunlight and effects of gravity were responsible for creation of that small size. All that mattered was that the seedling was small and that it grew slowly or was likely to be shaded by larger plants.

Therefore, the organism was an important part of the evolutionary process because it determined what occurred to it in the future. Similarly, the concept of quasi independence falls in line with this kind of reasoning because it focuses on the holistic effects of an adaptation upon the entire organism and the organism and its environment. In the analysis of this concept, one realises that the organism is the main focal point in natural selection. This was the same thing that Lewontin kept advocating for in his approach to evolution.

Lewontin opposed the fact that organisms were objects of external forces by explaining that the natural environment could be altered to suit the needs of organisms also. For example, he often explained that an organism’s niche can be altered in so many ways to suit its needs. For example, insects have the choice of selecting a wide range of leaves, but a number of species of leaves are actually never eaten by those insects. Alternatively, snakes could have had the options of crawling and eating grass, but they do not (Levins and Lewontin 98).

There are certain biological and physical traits in the organism that determine what niche an organism will require. This explains why it is not plausible to argue that a niche exists prior to an organisms’ existence. Therefore, the organism will determine what is relevant to it. It is the integrated whole and not some specific genetic factors that will affect its future.

Likewise, in quasi independence, he argues that the organism still determines what is relevant to it in terms of adaptation. Although mutations can occur in a variety of ways, it is only the ones that meet the need of the organism that can be defined as adaptively relevant. This means that he was giving focus to the whole rather than the particular traits he was talking about.

Conclusion

Quasi independence was a necessary concept because it provided an explanation about relative usefulness of mutations. This phenomenon was in tandem with Lewontin’s overall view of evolution because the organism determined the relevance of the mutation and it was also the focal point in the concept.

Work Cited

Levins, Richard and Lewontin, Richard. On evolution. Harvard: HUP, 1985. Print.

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