Group Dynamics

"Within groups, selfish individuals win. However, groups of altruistic individuals always beat groups of selfish individuals.” - EO Wilson

Would the more selfish emerge to lead groups of altruistic individuals?

Will an individual's degree of altruism depend on the circumstances?  Inside of an altruistic group, what happens with the principal-agent problem?

Are altruistic people always under pressure from selfish individuals?  Or will selfish individuals always freeride with altruists?

I think EO Wilson's point is that selfish individuals will waste time with zero-sum games because they need to feed their egos with hierarchy games.  The dynamism of the system would be interesting to see.