Demand sharing is a form of co-operative behaviours. It is the process of sharing that is not initiated by the giver, but rather by demands of the recipient.
Demand sharing has been observed in hunter-gatherer populations.
Evolution of demand sharing Edit
Free-riders pose a problem for the evolution of demand sharing behaviours, as individuals that do not hunt (or hunt, but do not share) still receive the food necessary for survival, without risking their health and well-being or spending energy for hunting. Possible solutions include:
Kin selection Edit
One possible explanation is Hamiltonian kin selection. Demand sharing might evolve if the altruists (individuals that share and hunt) provide food for their kin, thus making sure that copies of their genes are provisioned for the next generation.
Reciprocal altruism Edit
A reciprocal altruism approach would suggest that altruists share with other individuals with the expectation (implicit or explicit) that the free-riders of the present will reciprocate in the future.
Costly signaling Edit
The costly signaling approach suggests that demand sharing is an honest signal of quality, and actually a burden on fitness. Thus individuals (males) prove that their qualities can afford to bear this burden, and gain access to more females / mating opportunities / other status related benefits.
Tolerated theft Edit
The tolerated theft hypothesis suggests that the altruists do not want to share, but struggling to prevent thieving might be more demanding than just allowing others to take their share.
Punitive migration Edit
Another explanation might be punitive migration - moving away from free-riders. This includes the assumption that the free-riders cannot just follow other people from the same group.