Question

Mammals are the only animals that have hair. Would you consider the presence of hair in mammals to be an ancestral or derived trait among all animals? Why?

Answer 1

Answer:

derived trait

Explanation:

An ancestral (or primitive) trait/character is a feature inherited from the common ancestor of the species/group of interest, while derived traits are those that were absent in the last common ancestor of the group of interest. For example, considering mammals as the target group, the presence of hair is a shared derived trait relative to other vertebrates, i.e., amphibians, reptiles and birds. However, this trait (hair) is ancestral for humans since the genetically closest species to humans (e.g., chimpanzees), also have hair, and they have inherited this trait from a common ancestor.