Law of conservation of information
Law of conservation of information
Conservation of information for dummies
Common sense tells us that biological organisms are too complex to arise by natural processes. As William Paley noted in 1802, some objects show obvious features of design. In fact complex objects, such as airplanes and computers, are products of multiple designers; the number of designers tends to increase with complexity. This correlation is rarely extrapolated to natural objects.

For those with ideological commitments to design, evolution of complex objects is obviously impossible. The impossibility is reinforced by the second law of thermodynamics which states that net entropy (disorder) increases in any process. What's overlooked is that while net entropy increases, the entropy of one part of the system can decrease at the expense of the rest of the system. If evolution violated the second law of thermodynamics, physicists and physical chemists would universally reject evolution. Since most people are unfamiliar with thermodynamics, it's easy to overgeneralize the second law to convince them that scientific law supports intuitive conclusions.

A further objection to evolution is that mutations tend to be harmful. In point of fact a high proportion of mutations are neutral. Mutations are more diverse than most realize. In addition to DNA damage and simple synthesis mistakes they include deletions, insertions, duplications and recombinations. They include changes in regulatory genes as well as structural genes. The effect of harmful mutations is not to prevent evolution, but to slow it down. Purifying selection must (largely) eliminate harmful mutations.

William Dembski restated the second law in a more restricted way as "the law of conservation of information" with DNA specifically in mind. The notion, as applied to biology, is that information can't be created w/o input from a designer. The law is complicated by different definitions of information. Simple changes like duplications occur spontaneously. These increase the total amount of DNA, but have little effect on complexity. Information as defined by complexity (Kolmogorov) can increase by randomizing sequences. The significant information, however is "useful" information, which Dembski calls "complex specified information." This is a misleading phrase however since the product of evolution is specified at the level of function, not at the level of information (DNA). In other words, sequences vary at random and are selected by the functions they specify rather than by the specific sequence of DNA. In fact many different DNA sequences can specify the same function.

In point of fact biological systems readily generate complex information. The adaptive immune system is a striking example. It generates genes which produce antibodies to foreign substances, including synthetic chemicals that don't occur in nature. The immune system produces a great variety of antibodies and does so over a period of days to months. Dembski has said little of his "law" in the last few years, but intelligent design promoters continue to use it.