Responding to the impact of introduced species, in Hawaii and elsewhere, is just one area where evolutionary theory can affect public policy. Many other examples can be cited. Many pathogenic microorganisms are evolving resistance to the drugs that have been used to control them, leading to outbreaks of disease. The AIDS virus changes its genetic makeup so quickly within its human hosts that the drugs that have been used to counter the virus gradually lose their effectiveness. Agricultural pests have evolved defenses against pesticides, and based on our understanding of evolution they will continue to do so.

The only way to counter these threats effectively is to anticipate the ability of populations of living things to change over time. For example, evolutionary theory points toward strategies that can greatly reduce the development of antibiotic resistance, such as reducing the overall use of antibiotics by humans and curtailing the use of antibiotics in agricultural animals eaten as food.

An understanding of evolution is essential for another reason. As we learn more about the natural world, we will have greater potential deliberately to intervene in that world. Researchers already have begun to make specific changes in the DNA sequences of plants and animals to increase agricultural productivity. Soon they are likely to gain a comparable ability to change the DNA sequences of human cells. Wise decisions about when and how to use such knowledge will require a sophisticated grasp of evolutionary theory.

Apart from its practical applications, the theory of evolution has proven to be one of the most important unifying ideas in modern science. The basic mechanism at the heart of evolution—the differential reproductive success of organisms with different heritable traits—has profound implications throughout all of biology. Evolutionary theory is even central to such challenges as understanding the origins of humans and the evolution of the human brain. That such a simple mechanism could produce such complex outcomes provides a key insight into the workings of biological systems.

The flora and fauna of the Hawaiian islands offer just one example of how the processes of evolution have shaped life on earth. As such, the history of evolution in Hawaii demonstrates how powerful the concept can be in explaining what we see around us. The study of biological evolution has produced knowledge that is not only immensely useful but profoundly beautiful. It has deepened and enriched our view of living things— whether considering the plants and animals of Hawaii or the more than three billion years of life's history on this planet. As Charles Darwin wrote in the final sentence of On the Origin of Species, “There is a grandeur in this view of life, with its several powers, having been breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”