How does the idea of a common ancestor help support the theory of evolution?

The concept of a common ancestor in evolution suggests that all life on Earth shares a common origin, providing a framework to explain the diversity of species through gradual changes over time. It supports the theory of evolution by showcasing the interrelatedness of all organisms and the branching patterns of descent that have led to the vast array of species we observe today. By tracing back to a common ancestor, scientists can understand the evolutionary relationships among different species and how they have diverged and adapted over time.