Final answer:
Synapomorphies define shared derived characteristics, while autapomorphies and ancestral characters help determine the relationships among members of a clade.
Step-by-step explanation:
Synapomorphies define shared derived characteristics however autapomorphies and ancestral characters (plesiomorphies) help determine the relationships among the members of a clade. Ancestral characteristics are traits that are found in the common ancestor of the species being classified, while derived characteristics are traits that are only found in the groups being studied. By using cladistics and phylogenetic trees, biological anthropologists can identify and analyze these characteristics to understand the evolutionary relationships between different groups.