Assortative mating can help maintain or increase any endowment. Think of that as being a within-family/smaller-scale version of the existing genetic gradient by SES (eg "The Genetics of Success: How Single-Nucleotide Polymorphisms Associated With Educational Attainment Relate to Life-Course Development" https://www.gwern.net/docs/genetics/correlation/2016-belsky.... , Belsky et al 2016; "Genetic analysis of social-class mobility in five longitudinal studies" http://www.pnas.org/content/early/2018/07/03/1801238115 , Belsky et al 2018a.)