Many religious beliefs do not rely on evidence gathered from the natural world. On the contrary, an important component of religious belief is faith, which implies acceptance of a truth regardless of the presence of empirical evidence for or against that truth. Scientists cannot accept scientific conclusions on faith alone because all such conclusions must be subject to testing against observations. Thus, scientists do not “believe” in evolution in the same way that someone believes in God.
How can random biological changes lead to moreadapted organisms?
Contrary to a widespread public impression, biological evolution is not random, even though the biological changes that provide the raw material for evolution are not directed toward predetermined, specific goals. When DNA is being copied, mistakes in the copying process generate novel DNA sequences. These new sequences act as evolutionary “experiments.” Most mutations do not change traits or fitness. But some mutations give organisms traits that enhance their ability to survive and reproduce, while other mutations reduce the reproductive fitness of an organism.
The process by which organisms with advantageous variations have greater reproductive success than other organisms within a population is known as “natural selection.” Over multiple generations, some populations of organisms subjected to natural selection may change in ways that make them better able to survive and reproduce in a given environment. Others may be unable to adapt to a changing environment and will become extinct.
Aren’t there many questions that still surround evolution? Don’t many famous scientists reject evolution?
As with all active areas of science, there remain questions about evolution. There are always new questions to ask, new situations to consider, and new ways to study known phenomena. But evolution itself has been so thoroughly tested that biologists are no longer examining whether evolution has occurred and is continuing to occur. Similarly, biologists no longer debate many of the mechanisms responsible for evolution. As with any other field of science, scientists continue to study the mechanisms of how the process of evolution operates. As new technologies make possible previously unimaginable observations and allow for new kinds of experiments, scientists continue to