Apes and old world monkeys have the same dental formula 2.1.2.3. this is what kind of homology
The Correct Answer and Explanation is:
Correct Answer: Synapomorphy
The shared dental formula of 2.1.2.3 among apes and Old World monkeys is an example of a synapomorphy. A synapomorphy is a type of shared derived trait that evolved in the last common ancestor of a group and is present in all of its descendants. This kind of homology helps define a clade—an evolutionary branch on the tree of life.
The dental formula 2.1.2.3 refers to the number and arrangement of teeth in each quadrant of the mouth: two incisors, one canine, two premolars, and three molars. This pattern is characteristic of Catarrhines, a group that includes apes (such as humans, gorillas, and chimpanzees) and Old World monkeys (such as baboons and macaques). This formula contrasts with the 2.1.3.3 formula found in Platyrrhines, or New World monkeys.
The significance of this shared dental pattern lies in its evolutionary implication. Since both apes and Old World monkeys possess the same formula and this trait is not present in more distantly related groups, it must have originated in a common ancestor that lived after the split from New World monkeys. The presence of this trait in both lineages implies descent from that common ancestor, supporting their classification within the same clade.
The term synapomorphy is distinct from other homology-related concepts. An autapomorphy refers to a derived trait unique to one lineage. A plesiomorphy is a primitive or ancestral trait shared by multiple groups but not useful for distinguishing between them. In contrast, a synapomorphy is particularly important for identifying evolutionary relationships and constructing accurate phylogenetic trees.
This shared dental trait plays a crucial role in primate classification and understanding evolutionary relationships among different primate groups. By examining such features, scientists can trace lineage divergences and refine the understanding of primate evolution.
