One conspicuous feature of humans is the massive scale of our social cooperation. Which of the following is the most accurate and complete description of the ultimate causal origins of this human property?

a. Humans are the first species to find a large-scale solution to the universal conflict of interest problem, resulting from the inadvertent evolution of the cognitive virtuosity to understand this solution.
b. Humans are the first species to evolve the elite language capabilities essential to the communication and negotiation underlying an expanded scale of social cooperation.
c. Humans are the first species to find a large-scale solution to the universal conflict of interest problem, resulting from the inadvertent evolution of cost-effective social coercion in our lineage.
d. Humans are the first species to evolve the elaborate ethical sense necessary to support mutual aid and cooperation between non-kin conspecifics.