Assignment 3: Evolutionary Spandrels
Ashlyn Henderson: 27204648; Section: ANT3514C-4E34(17640)
In Gould’s and Lewontin’s article, The spandrels of San Marco and the Panglossian paradigm: A Critique of the Adaptationist Programme
, they introduce an interesting perspective on the roles of constraints in evolution. This idea of constraints is in direct conflict with the adaptationist approach, which tends to attribute every trait to natural selection exclusively, leaving no room for the exploration of alternative explanations, such as constraints. To further explain this idea of constraints, the authors introduce the idea of “spandrels”, which are an architectural byproduct resulting from the supporting of arches. Using this idea of spandrels, the authors argue that some traits are the byproducts, or constraints, of other adaptations, rather than exclusively natural selection. This idea that the authors have proposed has also directly challenged the original Panglossian Paradigm. The idea of the Panglossian Paradigm is that every trait specifically evolved as the best solution to a specific adaptive problem. The main critique of these original concepts is that they don’t take into account other forces that may act on the development of a trait. Additionally, they over-rely, as well as overemphasize adaptation. Meaning they tend to attribute every trait as an adaptation. However, for scientists to classify a trait as an adaptation, they would need to consider the following information: is there a selective advantage to this trait? Meaning, does this trait result in more reproductive success or better survival? The genetic basis of the trait is also crucial: is this trait heritable? A heritable trait strengthens the argument for natural selection and therefore adaptation. There should also be supportive studies in regards to the trait being adaptive. It is also vital to consider alternative explanations for the trait: was it a byproduct of another adaptation? A result of a non-adaptive process? Furthermore, understanding the context of the development of the trait is another important aspect of being able to classify it as an adaptation, as well as understanding the evolutionary history of a species. Understanding the evolutionary history of a species is by far the most important aspect of classifying a trait as an adaptation. By understanding the evolutionary history of a species, scientists are more able to identify whether or not certain selective pressures or even environmental changes led to that evolutionary path of a trait. Additionally, it allows for additional insights into a trait, such as origin and function, that prove to be valuable to scientists. Knowing and understanding the origins and functions of a trait could allow scientists to better understand the significance of said trait. Consequently, understanding the evolutionary history of a species enables scientists to better discern what caused a trait. Whether it was natural selection, as with the adaptionist approach, or due to other constraints as discussed by Gould and Lewontin.
Constraints also play an important role in the evolution of species. Constraints can influence the evolutionary trajectory of a species and shape the variation available within a population and by doing so, constraints in a way contribute to the wonderful diversity seen in life. Furthermore, the idea of constraints urges a more multidisciplinary approach to the study of evolutionary biology, including drawing insights from genetics and paleontology, to name a couple of fields. Additionally, this means that scientists should also consider more non-
adaptative processes. For example, genetic drift. Instead of relying exclusively on natural selection as the answer to all trait formations. By embracing the concept of constraints, scientists can better refine their hypotheses and better avoid such oversimplified explanations that lack real
insight.
