Aggression may not be the most optomistic way of doing this as it has high costs. Ess, includes a variety of complex behaviour which are non aggressive. Kin selection is helping close relatives with some of the same genes as you have to evolve i.e. allowing copies of the same genes to continue. This will occure maybe even with some cost to yourself. As females produce fewer gametes they take more care over them than males do.
Males seem more intrested in increasing the number of their genes in the next generation.
This is as far as I have got. I found the chapter on altruism quite confusing. Does the book go on to describe game theory as this seems important.