In the context of evolution, what does a common ancestor signify?

A common ancestor signifies the most recent shared ancestor of two species. This concept is central to understanding the evolutionary history and relatedness between different species. It emphasizes that all living organisms share a genetic heritage that can be traced back to earlier life forms. By identifying a common ancestor, scientists can create evolutionary trees, often referred to as phylogenies, which illustrate the relationships and divergence points of various species over time.

In evolutionary biology, identifying a common ancestor helps explain the similarities and differences that exist among species today, as genetic variations and adaptations arise from this shared lineage. Thus, when considering the evolutionary relationships of organisms, the notion of a common ancestor is essential for understanding how species have evolved and adapted over millions of years.