Humans have studied living things throughout history. For most of this time, our study was simply an effort to identify species and behaviors that would support human survival- either in terms of hunting, agriculture or predator avoidance. But over the past 500 years, human use of scientific inquiry has broadened and deepened the understanding of biology. Around 150 years ago, acquired biological knowledge reached a tipping point, making possible the theory of evolution, as proposed by Charles Darwin.
In the centuries leading up to Darwin's book "On the Origin of Species," scientists had devised tools such as the microscope, and had brought back to Europe countless biological samples for study-as well as fossils that revealed the strange creatures of earlier times. Especially helpful for Darwin was his own sample-taking while on board the Beagle, a research vessel which visited, among other places, the Galapagos Islands, offering him firsthand examples of how island isolation accelerates the process of species differentiation.
Evolution is a system of ideas which represents a sudden change in human understanding of the living world. Before evolution, plant and animal species were identified by humans as useful or dangerous, and in some cases, relatedness was noticed. For example, humans throughout history have noticed that cats and tigers look similar, as do wolves and foxes. But evolution provides an understanding of biology as a network of species that gradually change over time in response to environmental factors. Post-Darwin science research has actually provided the information that Darwin himself had no way to discover-how the chemical DNA in the cells of living things controls inherited characteristics. Time is the critical element revealed by evolution. Rather than a sort of "stamp collecting" exercise of collecting and identifying countless plant and animal species and how their tissues work, evolution reveals a vast tree of inter-related life that is descended from a few tiny ancestors in the distant past.
In recent decades, Christian religious elements in western nations, primarily the USA, have attempted to refute evolution's importance as a key concept in biology. In pushing "equal time" for intelligent design or creationism, activists have reduced the emphasis on evolution in public school biology classes in many regions of the United States. Many biologists feel threatened by these political efforts to reduce the teaching of evolution in public schools. Their perception is that biology must be taught as a unified and up-to-date body of knowledge, and that omitting or undermining evolution turns biology into a discipline that no longer reflects a global understanding. Teachers of biology point out that people who reject evolution, then visit their pharmacy for a flu shot, are contradicting their own beliefs-because the annual changes to the genetic makeup of the prevailing strain of flu virus are an example of rapid evolution.
In the end, faith in a supreme being actually does not require humans to reject evolution. Scientists, many of whom are Christian believers themselves, struggle to convey this idea. But the political battles continue on a state government level in the USA, with the result that some students are taught a thorough and accurate version of evolution, while others are taught a dumbed-down version that provides opportunity for discussion of "intelligent design."
Evolution by Edward J. Larson (New York: Modern Library, 2004)
Why Evolution is true by Jerry Coyne (New York: Viking, 2009)