 A higher effective population size causes more incongruent gene trees.Therefore, if the internodal time span is known, the ancestral effective population size of the common ancestor of humans and chimpanzees can be calculated.When each segment was analyzed individually, 31 supported the "Homo"-"Pan" clade, 10 supported the "Homo"-"Gorilla" clade, and 12 supported the "Pan"-"Gorilla" clade.