This edition: Macroevolution
As a theory, evolution is constantly being tested and evaluated. Scientists explain that each piece of new evidence contributes to completing a picture of life as it developed from the beginning—a dynamic and continuing process over a vast span of time. Macroevolution is the larger picture of species’ changes over time, their patterns and trends. Evidence of this evolutionary connection is found in the fossil record.
Paleontologists Eric Scott and Kathleen Springer explain how discovering fossils gives one a “snapshot in time” of the animals and ecosystems of an era. Fossils give clues to phylogeny, how one animal species is related to another.
Next, the concepts of homologous structures and shared characteristics are described by Dr. Blaire Van Valkenburgh. By studying the teeth and bones of ancient wolves and saber-tooth cats, she is able to reconstruct these animals that disappeared long ago. Further, Dr. David Bottjer discusses extinctions in general—why they occur and why the history of life on Earth is dotted with mass extinctions.
In conclusion, Dr. Russell Doolittle and Dr. Stanley Miller explain the unique combination of chemical, temperature, and atmospheric conditions that became the criteria for the origin of life on Earth.