Meyer claims that specified complex information can only arise from an intelligent source, justifying that claim by citing a series of examples. One of those examples is computer code. In my previous post, I suggested that this was not an adequate example because of fundamental differences between computer code and DNA information. An obvious question is whether there is an example of specified complex information that is not derived from an intelligent source but solely from physical or chemical functionality. In this post I would like to offer just such an example.
The magnificent example of antibodies was presented by Dr. Craig Story in the December 2009 issue of Perspectives on Science and Christian Faith, Vol. 61, No. 4, p.221. (if you aren’t a member or don’t have a subscription, copies are available from the ASA office for $10 plus shipping and handling; contact email@example.com.) In his article, Craig explains how the immune system works, focusing on the importance of the inherent randomness in the process. In this post, I would like to offer a physicist’s interpretation of his paper, with a focus on the information content. Craig has graciously reviewed these comments and corrected my errors in biology.
Stem cells in our bone marrow continuously produce a population of pre-B cells, so called because they are precursors to B cells, which manufacture antibodies when mature. These pre-B cells are all identical and have the same antibody gene DNA. This population therefore has a relatively low information content. All the complexity is within the cell and there is no diversity in the population of cells. As the pre-B cell population prepares to moves into the body, the cells undergo a transition into B cells. In the process, key segments of DNA in each cell are rearranged randomly to form a unique and novel DNA sequence. The process is described in detail in Craig’s paper. It is a constrained process so that the resulting antibody protein is always a particular folded configuration that may have affinity to an antigen, but the gene segments are randomly rearranged and joined to alter the magnitude of the affinity. The result is a population of B cells, each one of which is different in terms of its antibody DNA. This means that we have a transformation of a low information population of pre-B cells to a high information population of B cells, with reference to their antigen-binding abilities. The complexity has increased dramatically but we do not yet have specificity.
As a B cell moves through the body, it may or may not encounter an antigen with which it has affinity. If it does not, the B cell dies and that particular configuration no longer exists in the body. However, if an antigen appears with which a B cell has some degree of affinity, the B cell will attach to the antigen. In this case, that B cell will reproduce through cell division to create clones of itself. This process occurs throughout the population of B cells with the result that only B cells with some affinity to the environment of antigens survive. This is a basic level of specificity.
There is another level of specificity that Craig describes. A first-responder B cell usually will have a relatively small degree of affinity to an antigen. As this cell reproduces itself, an enzyme enhances the mutation rate of only the portion of the antibody genes that determines the affinity. In some cases, mutation rates can reach as much as one nucleotide per cell division. This means that the subpopulation of this particular B cell grows with a dynamic diversity of various degrees of affinity to that antigen. The cells with the strongest degree of affinity will preferentially attach to the antigens, leaving those with weaker affinity without antigens and therefore a death sentence. Over time, this subpopulation will be predominantly one with strong affinity to this particular antigen. This, in a nutshell, is why vaccines work.
In the bigger picture, this example shows how a homogeneous population of pre-B cells is transformed to a dynamically diverse population of B cells, with a tremendous increase in information content. This complex information then becomes highly specified by fine-tuning to match the antigens to which they are presented. The result is a high degree of specificity and complexity with no involvement of an intelligent designer as an immediate cause. This does not, of course, preclude the sustaining involvement of an Intelligent Designer at a metaphysical level.
Craig points out the critical role of randomness as a key characteristic of the cellular processes involved in the immune system. The random process of gene rearrangement is necessary to ensure a sufficiently broad range of binding specificities, such that some of them are almost sure to bind to one part of each pathogen. His example also illustrates clearly how highly complex and highly specified information is derived directly from a population of relatively low-information cells. Hence, the argument that Meyer makes that all complex specified information comes from an intelligent source does not withstand scrutiny.
The antibody example is a beautiful illustration of the basic processes of evolution. It begins with the common ancestry of the stem cells that produce an ancestral population of pre-B cells that are essentially identical. Descent with random variability occurs in the generation of the B cells, which are all unique with respect to their antibody gene DNA. Natural selection describes the way in which B cells that do not bind to an antigen will die while those that do bind to an antigen proceed to reproduce clones. The random variability of the dynamically diverse population of antibodies ensures the formation, within a short period of time, of antibodies with affinity to virtually any antigen. The subsequent way in which those B cells acquire stronger affinity to that antigen is a type of adaptation. Darwin suggested that these basic processes, operating over a long period of time, could account for the origin of species. Little did he suspect that these very processes are active continuously in our bodies on a relatively short time scale to provide a vital line of immunological defense.