Suele decirse que en épocas difíciles el mejor banco está en el estómago de tu vecino por aquello del hoy por ti, mañana por mí, pero parece que el ama de casa de la antropóloga Elizabeth Colson tenía teorías distintas en The Narrow Corridor. Interesante, cuando menos:

The Ghost in the Granary
In 1972, the anthropologist Elizabeth Colson was in the midst of her fieldwork among the Gwembe Tonga, a people of southern Zambia who had been stateless prior to the conquest of the region by the British (…). She was at a homestead collecting information when a woman entered and asked the resident housewife for grain. Both women were members of the same clan, but they lived quite far apart and only knew each other vaguely. In response to the request the housewife went to her granary and filled the visitor’s basket until it was overflowing and the visitor departed satisfied.
This type of generous sharing of food within clans, kin, or other types of groups is common among many stateless societies. It is interpreted by most anthropologists and many economists as a sign of deep-rooted customs and norms of cooperation and reciprocity. It also has a clear economic logic: today you help somebody from your clan, and tomorrow when you need it, they will help you. This is exactly how Colson initially interpreted this ostentatious generosity.
It was only later, when she observed a young man in the village receiving a disturbing letter from home, that Colson came to understand that the reality was rather different. She recorded in her field notes, “One evening, lights had been seen about his granary and his wives and brother had later found evidence that ghosts had urinated over the grain, an act which Tonga believe ghosts carry out only if sent by a sorcerer.” The likely aim of the sorcerer was to kill the man and his family. He lamented that “his ambition of the previous year—which had led him to work early and late in the large field he had planted—was now bringing him only a harvest of hate.” The same housewife, who was present, immediately grasped what was going on. Colson went on: “She thought someone must have visited his homestead and seen all the granaries, and she asked if he could remember anyone having stood to gaze at them or asking for food or making any comment about all that food.” The housewife concluded:
It is not safe to deny them. You saw me give grain to that woman who came the other day. How could I refuse when she asked me for grain? Perhaps she would do nothing, but I could not tell. The only thing to do is to give.
Not giving risked sorcery and violence. It was fear, fear from retribution and violence that would follow if she broke the norm, not some abstract notion of generosity, that made her give.