Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:…especially theorists adopting the prisoner’s dilemma as the main paradigm for explaining the evolution of cooperation (e.g., Cosmides and Tooby 1992; Trivers 1971), would argue that a mechanism with a relatively unconditional and indiscriminate care element may not evolve at all in an environment…
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