Final answer:
Gould and Lewontin's main point was a critique of the adaptationist view by proposing that not all traits in organisms are due to adaptive evolution, using the metaphor of spandrels in architecture.
Step-by-step explanation:
The main point of Gould, S. J. and R. C. Lewontin's 1978 paper, The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme, is a critique of the adaptationist view in evolutionary biology. Gould and Lewontin argue against the idea that all traits in organisms are the result of adaptive evolutionary processes. They propose that some features may arise as by-products of other evolutionary changes, rather than due to direct selection pressure for those features themselves. They illustrate this with the metaphor of spandrels in architecture, which are the spaces between arches that were not intentionally designed but came into existence as a result of the arches' construction.