“Our findings challenge all evolutionary models of cooperation that assume fixed social types. Consistent with models stressing the importance of contingent reciprocity, cultural learning, and social norms [27, 28, 29], we find that individuals’ cooperative behavior is best predicted by the cooperativeness of their neighbors. The findings highlight the flexible nature of human cooperation and the remarkable capacity of humans to respond adaptively to their social environments.”

Maybe a study should be done to determine why many Social Science professors have evolved to believe that humans are basically automatons and that human behavior is only a result of genetic shuffling and natural selection. Perhaps we could study their choice of marriage partners and analyze how the belief has come down through families. Questionnaires could be sent to the various universities to poll the professors and determine if the belief tends to be more rampant at some universities, which would indicate the clumping effect. (Jimplok 2011) DNA tests could be given to determine the degree of kinship of the professors where clumping was indicated.

An alternate theory is that the professors are endowed with conscious awareness and free will, and are thus able to analyze and select beliefs and behaviors that are true and helpful. If professors are so capable, why should not other people be capable, and why should the professors not observe that fact.

Preliminary studies indicate that the belief may not be as fixed as was previously thought, (See above quote) Perhaps the professors are beginning to learn.

In a hunter-gatherer group cooperation is beneficial even for a selfish person. Alone you're basically dead with all the higher level predators out there.
In our modern societies selfishness is often rewarded in different ways, so selfish people can more freely express their selfishness in modern societies. But I think people who are more cooperative and want to work with others outnumber those lonely wolves. The proportion of cooperative and selfish people might be subject to change, for instance by the values certain societies choose to emphasize more on, but the real number is not easy to find out because we don't know why people really act the way they do. Maybe a selfish person even in a modern society just acts selfless because he see more benefit in that kind of behavior.

It has always been my practice, in most cases, to be cooperative with other people when I can whether they have helped me in the past or not. When I find people who do not like to reciprocate, my cooperation with them is cut off. I have found, however, that the favor of my cooperation is usually returned. When I was a young man I got a job where I supervised about 50 people in a fairly large organization. I made friends with several other supervisors and found that supervisors generally would not allow the people in their charge to help other departments when it was needed. I ignored that and began having my people help out if I could afford to let people go from my department from time to time. Other supervisors then went out of their way to provide people to help me when my department needed help. I was quickly identified by management as being a top achiever but I'm not sure they ever knew why I was so productive. Cooperation is definitely contagious.

I don’t know of course but I’d guess universal.