Patterns, Predictions, and the Fossil Record: Key to the Public Understanding of Common Descent

Common descent proposes that all living things on Earth are connected by an unbroken series of ancestor/descendent relationships to a single common origin by a process of descent with modification. All life is genetically related such that it can be pictured as a branching tree or bush. This simple but powerful model makes predictions about the patterns of organic change that should characterize the history of life.

However, when presenting the evidential support for evolution to the public, too often we as scientists focus on the evolution of particular structures, or the discovery of some new fossil intermediate. This does not communicate well either the great explanatory and predictive power of evolution, or the vast body of paleontological evidence supporting common descent. The power of this evidence is in the historical, geographic, and anatomical patterns that are present. It is these patterns that need to be emphasized when presenting our science to the public.

Fossils provide windows into the anatomy and ecology of long-extinct species and enable us, in many cases, to reconstruct the evolutionary pathways that led to our diverse living biota. Fossils with transitional anatomical features are common within the fossil record. Furthermore, when looking backward through time using the fossil record, we see that representatives of different higher-level taxa become more "primitive", have fewer specialized characters, and appear more like the primitive members of other closely related taxa. This convergence in anatomy as we move back in time is precisely the expectation of common descent. These historical patterns extend deep into the past toward the trunk of the tree of life. By drawing public attention to these patterns and their predictive power, we can provide a more robust public understanding of the scientific community's confidence in evolutionary theory.