What is considered the common ancestor in a lineage?

A common ancestor in a lineage refers to the most recent species from which all individuals in that lineage have descended. This typically means that the common ancestor is the earliest species that can be traced back in the evolutionary history of the group. It is the node in the evolutionary tree that represents a shared ancestor for all descendant species, reflecting the connections and divergence of evolutionary paths.

In evolutionary biology, understanding the concept of a common ancestor is crucial as it helps to illustrate how different species are related through common descent. The focus on the earliest species emphasizes that this species laid the foundation for the diversifying processes that led to the variety of life forms we see today.