Some critics jokingly referred to the theory of punctuated equilibrium as "evolution by jerks", which prompted Gould to describe phyletic gradualism as "evolution by creeps." Evolutionary developmental biology Gould made significant contributions to evolutionary developmental biology, especially in his work Ontogeny and Phylogeny. In this book he emphasized the process of heterochrony, which encompasses two distinct processes: neoteny and terminal additions. Neoteny is the process where ontogeny is slowed down and the organism does not reach the end of its development. Terminal addition is the process by which an organism adds to its development by speeding and shortening earlier stages in the developmental process. Gould's influence in the field of evolutionary developmental biology continues to be seen today in areas such as the evolution of feathers. Selectionism and sociobiology Gould was a champion of biological constraints, internal limitations upon developmental pathways, as well as other non-selectionist forces in evolution. Rather than direct adaptations, he considered many higher functions of the human brain to be the unintended side consequence of natural selection. To describe such co-opted features, he coined the term exaptation with paleontologist Elisabeth Vrba. Gould believed this feature of human mentality undermines an essential premise of human sociobiology and evolutionary psychology. Against Sociobiology In 1975, Gould's Harvard colleague E. O. Wilson introduced his analysis of animal behavior (including human behavior) based on a sociobiological framework that suggested that many social behaviors have a strong evolutionary basis. In response, Gould, Richard Lewontin, and others from the Boston area wrote the subsequently well-referenced letter to The New York Review of Books entitled, "Against 'Sociobiology'". This open letter criticized Wilson's notion of a "deterministic view of human society and human action." But Gould did not rule out sociobiological explanations for many aspects of animal behavior, and later wrote: "Sociobiologists have broadened their range of selective stories by invoking concepts of inclusive fitness and kin selection to solve (successfully I think) the vexatious problem of altruism—previously the greatest stumbling block to a Darwinian theory of social behavior... Here sociobiology has had and will continue to have success. And here I wish it well. For it represents an extension of basic Darwinism to a realm where it should apply." Spandrels and the Panglossian paradigm With Richard Lewontin, Gould wrote an influential 1979 paper entitled, "The Spandrels of San Marco and the Panglossian Paradigm", which introduced the architectural term "spandrel" into evolutionary biology. In architecture,