However, in a interview, Lewontin said that Gould wrote the majority of the paper, and that he himself had made only "a lesser contribution" to it. It was written in a provocative and literary style that was unusual even compared to that of most other opinion pieces. Queller described the paper as "an opinion piece, a polemic, a manifesto, and a rhetorical masterpiece". The paper makes an analogy between these spandrels and the evolutionary constraints of living organisms, and the need to distinguish between the current use of a trait and the reason it evolved. Our noses were made to carry spectacles, so we have spectacles.
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Wagner called the paper "the most influential structuralist manifesto". The authors singled out properties like the necessary number of four spandrels and their specific three-dimensional shape. Gould and Lewontin proposed an alternative hypothesis: that due to adaptation and natural selection, byproducts are also formed. These byproducts of adaptations that had no real relative advantage to survival, they termed spandrels. In the biological sense, a "spandrel" might result from an architectural requirement inherent in the Bauplan of an organism, or from some other constraint on adaptive evolution.
In response to the position that spandrels are just small, unimportant byproducts, Gould and Lewontin argue that "we must not recognize that small means unimportant. Spandrels can be as prominent as primary adaptations". A main example used by Gould and Lewontin is the human brain.
Many secondary processes and actions come in addition to the main functions of the human brain. These secondary processes and thoughts can eventually turn into an adaptation or provide a fitness advantage to humans.
Just because something is a secondary trait or byproduct of an adaptation does not mean it has no use. In , Gould and Vrba introduced the term " exaptation " for characteristics that enhance fitness in their present role but were not built for that role by natural selection. Spandrels are characteristics that did not originate by the direct action of natural selection and that were later co-opted for a current use.
Gould saw the term to be optimally suited for evolutionary biology for "the concept of a nonadaptive architectural by-product of definite and necessary form — a structure of particular size and shape that then becomes available for later and secondary utility". Dennett argues that alternatives to pendentives, such as corbels or squinches , would have served equally well from an architectural standpoint, but pendentives were deliberately selected due to their aesthetic value. He argues it is not entirely clear what is and is not a spandrel.
He also argues all examples of spandrels, pendentives, corbels and squinches do actually serve a function; they are necessary to achieve something, but that necessity is exactly what epiphenomenalism denies. Causes of historical origin must always be separated from current utilities; their conflation has seriously hampered the evolutionary analysis of form in the history of life. The nature of the current utility of a structure also does not provide a basis for assigning or denying spandrel status, nor does he see the origin of a structure as having any relationship to the extent or vitality of a later co-opted role, but places importance on the later evolutionary meaning of a structure.
This seems to imply that the design and secondary utilization of spandrels may feed back into the evolutionary process and thus determine major features of the entire structure. The grounds Gould does accept to have validity in assigning or denying a structure the status of spandrel are historical order and comparative anatomy.
In the absence of historical evidence, inferences are drawn about the evolution of a structure through comparative anatomy. Evidence is obtained by comparing current examples of the structure in a cladistic context and by subsequently trying to determine a historical order from the distribution yielded by tabulation.
In this view, Chomsky initially pointed to language being a result of increased brain size and increasing complexity, though he provides no definitive answers as to what factors led to the brain attaining the size and complexity of which discrete infinity is a consequence. He suggests that universal grammar cannot be derivative and autonomous at the same time, and that Chomsky wants language to be an epiphenomenon and an "organ" simultaneously, where an organ is defined as a product of a dedicated genetic blueprint.
It shows no signs of design for attaining a goal such as long life, grandchildren, or accurate perception and prediction of the world", and "I suspect that music is auditory cheesecake, an exquisite confection crafted to tickle the sensitive spots of at least six of our mental faculties.
The Spandrels of San Marco and the Panglossian Paradigm