Variable ages of quartets. Randomly selected quartets (black lines) capture information about (A) young, (B) medium and (C) old time depths. For visual clarity, quartets are shown on a non-recombining genealogy, but the principle holds equally for ancestral recombination graphs.
Cox et al. BMC Genetics 2013 14:11 doi:10.1186/1471-2156-14-11