The sequence of steps leading to kin recognition in Gilbert’s (2015) model of histocompatibility. Histocompatibility gradually evolved by natural selection through steps 1–5, kin recognition evolving adaptively in the 5th step. Whether kin recognition used for histocompatibility is naturally rewarded in a 6th step is an open question.

  Part of: Gilbert OM (2020) Natural reward drives the advancement of life. Rethinking Ecology 5: 1-35.