How does phylogenetic analysis enable evolutionary history to be traced?

Snippets from Phylogenetic Interpretations of Primate Socioecology: with special reference to social and ecological diversity in Macaca by Leslie K. W. Chan

"In recent years, however, there has been substantial development in the application of phylogenetic methods to the analysis of behavioural, ecological and social patterns in diverse groups of organisms. One common approach, referred to as character mapping or character optimization method, consists of establishing genealogical relationships of the species being compared first, and then asking whether similar traits observed among species arose in a common ancestor and have persisted, or whether they arose independently due to convergent adaptation to similar environments. This approach emphasizes the importance of a species' evolutionary history in constraining both the features it curently displays and the subsequent directions and rates of evolution open to it.

A key assumption of this approach is that just as the evolution of morphological and life-history traits, behavioural and social evolution take place in the context of phylogeny. It follows that mapping or superimposing these biological or behavioural features on a well-established phylogentic hypothesis, we may estimate when, and how many times, an observed characteristic arose in the group being studied. We can also gain insights as to which features are highly conservative, and which are most liable. In other words, this approach allows us to compare similar traits across species and to distinguish those similarities that are most likely due to descent from a common ancestor from those that evolve independently."