even [August] Weismann, the father of neo-Darwinism, decided late in his career that directed variation must be invoked to understand some phenomena, as random variation and selection alone are not a sufficient explanation. This minireview will describe mechanisms of mutation that are not random and can accelerate the process of evolution in specific directions. The existence of such mechanisms has been predicted by mathematicians who argue that, if every mutation were really random and had to be tested against the environment for selection or rejection, there would not have been enough time to evolve the extremely complex biochemical networks and regulatory mechanisms found in organisms today. Dobzhansky expressed similar views by stating “The most serious objection to the modern theory of evolution is that since mutations occur by ‘chance’ and are undirected, it is difficult to see how mutation and selection can add up to the formation of such beautifully balanced organs as, for example, the human eye.”
The paper next introduces the idea that environmental stress causes directed feedback mechanisms to accelerate adaptation. The idea is that these mechanisms work together to expose DNA segments to mutations.
Many scientists may share Dobzhansky's intuitive conviction that the marvelous intricacies of living organisms could not have arisen by the selection of truly random mutations. This minireview suggests that sensitive, directed feedback mechanisms initiated by different kinds of stress might facilitate and accelerate the adaptation of organisms to new environments. The specificity in the series of events summarized by Fig. 3 resides entirely in the first step, which is meant to suggest a pattern of derepression elicited by a corresponding pattern of adverse conditions. Microorganisms in nature must be confronted simultaneously by a complex set of problems, for example, the threat of oxidative or osmotic damage together with suboptimum concentrations of many essential nutrients. Transcriptional activation of genes derepressed to various degrees would expose the nontranscribed strands to mutations and stimulate localized supercoiling. Vulnerable bases in the complex DNA structures resulting from supercoiled DNA will also contribute to localized hypermutation in the genes activated to cope with the stresses that initiate the above series of events.
So the idea is that that the environment not only creates life, but it continues to direct evolution by fine-tuning the DNA copying process. After all, organisms that can respond more effectively to environmental challenges would have an obvious advantage:
The environment gave rise to life and continues to direct evolution. Environmental conditions are constantly controlling and fine-tuning the transcriptional machinery of the cell. Feedback mechanisms represent the natural interactive link between an organism and its environment. An obvious selective advantage exists for a relationship in which particular environmental changes are metabolically linked through transcription to genetic changes that help an organism cope with new demands of the environment.
In other words, evolution does not merely occur by random events. It occurs via complex mechanisms which evolution first created. This work demonstrates how robust evolutionary theory is to falsified predictions. It also demonstrates the immense level of serendipity in evolutionary theory.