Families in which two parents raise their offspring are currently no longer seen as a harmonious unit. They rather represent a battleground shaped by evolutionary conflicts of interest among its members that are not perfectly related. This is particularly true for parents. Although parents temporarily cooperate to enhance offspring survival, each parent can gain extra benefits by transferring the largest workload to the partner. Parents thus need to negotiate about their investment to reach optimal cooperation. However, it is currently unclear how such negotiation can contribute to evolutionary stable levels of care. This is largely due to a lack of empirical knowledge about (1) how the negotiation process develops throughout a reproductive event, (2) sex differences in the costs and benefits of negotiation and (3) potential physiological constraints on cooperation.
By experimentally manipulating parental exploitation opportunities, sexual conflict intensity and family structures, I wish to fill and bridge these knowledge gaps. I further include a proximate view to examine the extent to which hormone profiles constrain negotiated levels of care. In doing so, I aim to increase our knowledge about the mechanisms that lead to conflict resolution and set the stage for the next generation of theoretical negotiation models explaining evolutionary stability of biparental care.