Answer by Adam Nyhan:
Let's go way, way back in time to the Neanderthals — the earliest of the pre-agricultural groups of peoples. One fascinating thing about Neanderthals is that they appear to be the first hominids who cared for physically disabled members of their communities. How do we know that they did? Because many Neanderthal fossils have been found that show severe bone fractures that pre-dated the individual's death by many years.
Neanderthals lived a brutal life by today's standards. Their skeletons bear injuries that lead modern forensic anthropologists to compare their injuries to those of rodeo riders. Very often, their skeletons show fractures that would have spelled certain, agonizing death — had they been without a community to help feed them afterwards. And yet bone growth evident in the fossils showed that they survived in many cases for years after these crippling wounds. The only explanation seems to be that their families, and perhaps others in the community, chose to care for them.
These unfortunate injured people were in some ways free-riders: unable to physically help generate food for the group, yet taking its limited food assets nonetheless. So it seems that in these communities, anyway, free-riding was not considered such a bad thing.