A recent paper in PLoS "Altruism in Forest Chimpanzees: The Case of Adoption" has a few things to say about costly altruism – adoption of orphans, the socio-economic conditions required for altruism, and raises the questions of why human males aren’t primary caregivers half the time, as half the chimp adopters of unrelated infants were male.
Males managed to give good care, sometimes for years, measured by comparing the development of adopted and non-adopted kids, and were prepared to adopt non-related kids, even those not completely weaned. In a troop that walks often, carrying an unweaned infant on your back (for many months), preparing food, searching for and waiting for an infant, is a significant investment, particularly when the rest of the troop don’t do these things for kids when the kid has a parent, natural or adoptive.
It’s a tough life for the Tai troop compared to other troops. Tais are in an area with more leopards and many diseases such as anthrax and ebola, yet they show much greater altruism than other wild troops who have it easier, and certainly more than captive chimps who enjoy 24/7 valet service from humans.
Empathy and a willingness to go out of one’s way for unrelated unfortunates – mateship in other words – what we deem an Australian characteristic, developed in tougher times, while in today’s relatively luxurious times, getting each single cent of tax for the common wealth from voters is a nigh-impossible task if election campaigns are any guide.