Comment 5 by vanghelie :

Can someone who understands this expand a bit and explain (to a layman) how kin selection explains the evolution of these traits?

The way I see it, something like "individuals who share this gene cooperate more" does not make sense as the individuals themselves do not reproduce; the only relevant consequence of their cooperation (or lack there of) is how well they can "help" the queen reproduce.

For a good explanation of this see The Selfish Gene, however, the (i might be a little wrong about details) short answer is that, in haplodiploid species (like ants) females share more genes with their sisters than with their own offspring. This means that it is in the "interest" of the "selfish" genes to increase the number of siblings of an individual at the expense of offspring since this is the most efficeint way to propogate the maximum number of copies of themselves into the next generation.

see the comments in the linked article for a fuller explanation