All living beings have developed over time from ancestors through a series of changes. That life has evolved over long periods of time, with all forms of life related to one another, is a scientifically well-established fact. Along with researchers throughout the world, scientists at the Smithsonian’s National Museum of Natural History have contributed significantly to understanding the patterns and processes of evolution in humans and other species of animals and plants.
As one of the world’s leading research museums, the National Museum of Natural History has the responsibility to share with the public the latest research on the process of evolution. It is not the Museum’s responsibility or intent to determine how visitors relate this information to their own religious or personal views.
The Science of Evolution
In informal language, the word “theory” often implies an idea without much factual substantiation. But a “scientific theory” is different: Based on repeated observations, experiments, measurements and discoveries, a scientific theory represents the most logical and best-tested available explanation for natural phenomena. A scientific theory examines and explains why and how specific natural phenomena occur—for example, why there are differences among species, how lineages of species have changed over time and how species are related to each other.
Evolutionary theory provides a logical framework for making sense of the great diversity of organisms on earth—for understanding both differences and similarities among them. For example, the theory of evolution (sometimes referred to as descent with modification) helps explain three distinct patterns that we see in the world around us:
- The diversity of life (biodiversity)—there are millions of different kinds of organisms and life forms, and millions have existed for varying lengths of time during Earth’s long history
- The similarity of life—even species that look very different and are only remotely related share remarkable aspects of anatomy and molecular chemistry, such as DNA shared by nearly all life forms
- The history of life—fossilized remains of ancient organisms found embedded in successive layers of rock of different ages show many sequential, step-like changes that have occurred over more than three billion years
Evolution is not a matter of mere chance or random change. It is shaped by the process of genetic change, the production and survival of new adaptations and organisms, changes in the frequency of genetic variations, and results in the wide variety of ways in which organisms adapt to and survive in their diverse and changing surroundings. Genetic variation—amply documented in nature—is the raw material for how living beings change.
Scientists have learned how humans have developed over time from examining fossil remains of earlier humans, archeological finds, and the evidence of genetics. All of the resulting information supports the idea that humans have emerged by a process of change over time, and that humans are related to all other lifeforms.
Although there is no scientific controversy about the fact that evolution occurs, our understanding of the details progresses as scientists continue to learn more from combined geological, morphological, and molecular data. Continued research has filled in many of the earlier gaps in the explanation of evolution; for example, many of the gaps in the fossil record have now been filled in by new discoveries. Today’s rapidly increasing understanding of molecular biology and genetics also now provides a much more complete understanding of the evolutionary process.