Identity fusion is remarkably similar to the extensively validated construct of communal sharing, proposed in 1991. Both posit that notions of oneness/unity/equivalence with others underpin altruism. However, we argue that oneness/equivalence instantiates an evolved, innate relational form, marked and constituted by cultural practices making participants’ bodies substantially the same. It is intuitive from earliest development, often encompasses persons whom one has never met, and results mostly in caring.