In the specific case of height increases it is possible that heterosis played a role; genes correlated with greater height are more often dominant than recessive, and as modern transport led to people mating further afield rather than mainly marrying others within their village average homozygosity decreased.
In the specific case of height increases it is possible that heterosis played a role; genes correlated with greater height are more often dominant than recessive, and as modern transport led to people mating further afield rather than mainly marrying others within their village average homozygosity decreased.