Cohabitation, convergence, and environmental covariances

Abstract
Temporal variation in traits has long been a central theme in epidemiology. However, human geneticists have largely avoided this topic. Recently, several authors have shown how temporal variation in relative‐to‐relative covariances can be accommodated within the framework of variance components analysis. The present paper attempts to clarify the mathematics implicit in their approach. A stochastic mechanism is discussed that causes covariances to converge or diverge exponentially fast as relatives cohabit or lead separate lives.