I wonder why you were initially downvoted? Anyway, to quote from Williams: "I see no reason why a conscious motive need be involved. It is necessary that help provided to others be occasionally reciprocated if it is to be favored by natural selection. It is not necessary that either the giver or the receiver be aware of this. ... Simply stated, an individual who maximizes his friendships and minimizes his antagonisms will have an evolutionary advantage, and selection should favor those characters that promote the optimization of personal relationships."

Robert Trivers expanded this idea and you can read his paper, "The Evolution of Reciprocal Altruism", here: http://www.cdnresearch.net/pubs/others/trivers_1971_recip.pd... Since then the evidence has continued to grow in support of the idea (at least in primates--birds and fish that Trivers suggest don't have as much evidence).

http://lesswrong.com/lw/kw/the_tragedy_of_group_selectionism... is a nice post on why group selection theories tend to be wrong by default and why you shouldn't really pay attention to them when they come up.

For people interested in evolutionary psychology I recommend Robert Wright's The Moral Animal, which does a good job covering the history of the field and offering explanations for a variety of behaviors. http://www.amazon.com/Moral-Animal-Science-Evolutionary-Psyc...

There are free riders and they are in balance with altruism.

I saw footage when some squirrels (or monkeys) ware picking up something tasty out of the shallow water. They had to be careful because there might have been predators in the water.

If individual spotted predator they yelled and whole pack ran to the trees.

But occasionally weaker individuals yelled even when there was no predator to drive away stronger individuals to get some food himself.

So they altruistically warned each other but there was free-rider in who occasionally abused the altruistic system for personal gain. He couldn't do that too much because other individuals would notice and kick his butt. So altruism and free-riding in nature can be in balance and still give obvious advantage in cooperation.

Maybe whole reason for the altruism is to create opportunity for future occasional free-riding for an individual.

There are many examples in human society when someone shown and loudly encouraged altruism just to free-ride on others where nobody was looking carefully.

If all, or even most of the citizens in your empire turn into free riders, the empire collapses. Certain types of groups like nations, startups, and schools of scientific thought, may be be inherently unstable on various time scales, yet that doesn't mean they don't arise, have dominating effects relevant to reproduction during their heyday, and that evolution doesn't need to adapt to the reality of their existence. That is to say, groups are not a unit of selection in the sense of natural selection. They are the context of selection.

Powerful social groups are a fact of life. Powerful enough to decide your fate, choose who you could or could not marry. We see them all around us. We see such organizations form, thrive, and die on a wide variety of scales, both in time and level of influence. If you can't network, you will wither in this and probably every other major society which ever existed. No want wants to partner with, or stay partnered with useless dead weight.

An example of a group of non-necessarily related individuals who share a common goal is an army. Soldiers may be more closely genetically related to many of their foes than they are to many of their comrades. Soldiers may be ordered to their deaths. Armies don't last forever, they don't have to. They exist to defeat other groups of people and impose some collective sanction. If a hypothetical free rider gene resulted in the formation of less effective armies, any population where such a gene predominated would be severely disadvantaged in war, and eventually massacred and/or enslaved.