Complex sentence: This reduction in the number of ancestors is pedigree collapse, it collapses the binary tree into a directed acyclic graph with two different, directed paths starting from the ancestor who in the binary tree would occupy two places.
Split into simpler sentences: This reduction in the number of ancestors is pedigree collapse. It collapses the binary tree into a directed acyclic graph with two different, directed paths starting from the ancestor who in the binary tree would occupy two places.