In this sense, a signal can carry information about a source without there being any biological system designed to produce that signal, nor any to use it once produced. When a biologist employs this sense of information in a description of gene action or of other processes, he or she is just adopting a quantitative framework for describing ordinary correlations or causal connections within those systems. So it is one thing for there to be a signal carrying information about a source; quite another to explain biological processes as the result of signalling. The familiar example of tree rings is helpful here. When a tree lays down rings, it establishes a structure that can be used by us to make inferences about the past. The number and size of the rings carry information, in Shannon’s sense, about the history of the tree and its circumstances (the technique, “dendrochronology”, is scientifically important). Despite the usefulness of the informational description, there is no sense in which we are explaining how the tree does what it does in informational terms. The only reader or user of the information in the tree rings is the human observer. The tree itself does not exploit the information in its rings to control its growth or flowering. Similarly, we might note ways in which the distribution of different DNA sequences within and between biological populations “carries information about” the historical relationships between those populations, and the histories of the individual populations themselves. Using this information has given evolutionary biologists a much richer and more reliable picture of the history of life (for a good introduction to these uses see Bromham 2008). It has been argued, for example, that the greater diversity in mitochondrial DNA in African populations, in comparison to other human populations, is an indicator of a comparatively recent human dispersal from an African origin. In making these inferences, informational concepts can be useful tools. But this is just a more complicated version of what is going on in the case of tree rings. The appeal to information has an inferential use that is no way explanatory. A large proportion of the informational descriptions found in biology have this character.