Complex sentence: Culture can be defined as a system of socially transmitted behaviors that are demonstrated in most or all individuals in the relevant group at a particular site, but absent in at least one other ecologically similar site.
Split into simpler sentences: Culture can be defined as a system of socially transmitted behaviors. An action is considered cultural is if is demonstrated in most or all individuals in the relevant group at a particular site, but absent in at least one other ecologically similar site.