Fig. 2.

Illustration of the evolutionary history of a particular genetic variant represented by a phylogeny tree. In the phylogenetic tree, time moves from past (left) to present (right). Suppose some of the variants represented in this tree are associated with a trait. Then, a large covariance is expected among trait values from 2 variants (eg, the blue diamonds) sharing a large portion of their evolutionary history (shown by the branches in blue). In contrast, the 2 variants denoted by black circles share a smaller portion of evolutionary history, so that little covariance in the corresponding trait values is expected