In the mid-eighties, John Cairns, a British-born geneticist at Harvard’s School of Public Health, carried out an experiment that would set off one of the largest arguments in modern biology.

The plan of the experiment was simple enough — to place some bacteria in a tight spot. He selected bacteria with a genetic defect rendering them unable to digest lactose, the sugar present in milk, then introduced them into a batch of Petri dishes containing cultures whose only food-source was lactose.
Without any digestible food, the bacteria faced death by slow starvation.
According to orthodox science and the neo-Darwinist view of natural selection, the bacteria would not be able to colonize; without a food source to drive metabolic processes, they could not carry out normal reproduction.
Nevertheless, in every Petri dish, Cairns found a goodly number of thriving colonies.
Life-changing mutations
When Cairns tested for genetic changes in his colonies, he found that a single type of gene had changed – those preventing lactose metabolism.
Identical changes in just those genes had occurred within every new colony in every Petri dish. Cairns had confirmed that none of the original bacteria had contained a lactose-digesting mutation prior to the experiment.
Through some unknown mechanism, the bacteria had activated life-saving mutations in direct response to an extreme environmental crisis, and these mutations had saved their lives.
The bacteria had defied the central dogma: they had evolved purposefully, not randomly, in order to restore balance and harmony with their environment. Somehow the extreme environmental conditions had caused changes in genes, enabling the bacteria to digest the only food available to them.
In 1988, Cairns published his findings in the prestigious journal Nature under the droll title “The Origin of Mutants,” a flippant nod to Darwin. Cairns proposed that cells within organisms have the ability to orchestrate their own “directed mutation,” rapidly adapting to a changing environment.
Although Cairns, the discoverer of the structure and replication of the E. coli genome, had great standing among his peers, his assertion that the environment could actually change genes sparked a decade-long protest in the medical literature. American of journal Science dismissed his work as tantamount to “heresy.”
As other researchers looked closer, they discovered that, under environmental stress, a special enzyme in a bacterium cell gets activated, initiating a fevered copying process of cell DNA with a deliberate array of random mistakes, a mechanism now referred to as somatic hypermutation.
If any one of these mutated genes happens to be able to assemble a protein with the key to overcoming the environmental problem, the unthinkable occurs: the bacterium jettisons the original problem gene from its DNA and replaces it with the new gene.
This is the likely process by which bacteria continuously manage to outwit antibiotics. Although Darwin described mutation as random accident during the reproductive process, Cairns and other scientists after him have begun to show that the environment is constantly changing an organism, not simply through epigenetics as described by Dr Bruce Lipton (where the environment affects processes in the body that switch genes on or off) but directly by changing genes.
A two-way flow
Scientists have refined Cairns’s early ideas after discovering that information between genes, the rest of the body and the environment flows in a dynamic and interactive manner.
“The traditional mechanistic view held that the structure of biological molecules determines the actions of cells in some kind of linear fashion,” says James Shapiro, a professor in the Department of Biochemistry and Molecular Biology at the University of Chicago.
Genes change, says Shapiro, not from accidents — but through “natural genetic engineering,” or “adaptive evolution,” as it is now called, a constant dynamic process of adaptation between an organism and its environment.  
“Today we know that biological molecules change their structures as they interact with other molecules and these structural changes contain information about the external environment and conditions within the cells,” he adds.
All of the recent research on adaptive mutation and epigenetics casts a long shadow on the idea that illness is simply a case of having “good” or “bad” genes. Not only are the on–off switches for genetic expression controlled by environmental triggers, but disease of many varieties — cancer, inherited defects, dementia, suicide, schizophrenia, depression and other so-called ‘mental’ illness — all appear to be set off by influences outside our bodies.
Diet, a strong social network and community ties, purposeful work, mental stimulation, and an environment free of toxins and pollution may be far more important than the genes you are born with in determining the person you become and how healthy you are.