Molecular biology and evolution. Can genes explain biological complexity?

Although natural selection does not guarantee that organisms will increase in complexity as they evolve, it is apparent that the complexity of certain lineages, such as our own, has increased during evolution. Although we have an intuitive appreciation of biological complexity--often thinking in terms of morphological or behavioral complexity, or the variety of cell types in an organism--the term itself is notoriously hard to define. One could resort to algorithmic complexity, where the number of steps in the shortest possible algorithm that solves a given task has proven to be a convenient measure (1). In this case, complexity could be defined as the number of steps in the developmental program out of which the embryo is "computed." The snag here is that evolution is not an engineer but a tinkerer, so that there is no reason to expect that, for example, elephants have developed according to a minimalist program (2).