Evolutionary biologists suspect that genetic imprinting evolved through parent-offspring conflict. ...

Fetal development requires enormous energy investment, and in many species the degree of pre- and postnatal investment directly influences future maternal reproduction. From the point of view of the mother's evolutionary fitness, there should be a balance between present and future investment. In terms of the father's evolutionary fitness, however, his unborn offspring should take as much energy from the mother as possible to safeguard his present investment, since his future investments may not necessarily be with the same mother. Imprinting may have evolved as a result of conflict between the maternal and paternal genomes. (See Reik and Walter. 2001. Nat Genet. 27:255-256; PMID 11242103.)