WE ARE ALL DESIGNIST NOW:

At the end of the eighteenth century, the French naturalist Jean-Baptiste Lamarck noted that life on earth had evolved over long periods of time into a striking variety of organisms. He sought to explain how they had become more and more complex. Living organisms not only evolved, Lamarck argued; they did so very slowly, "little by little and successively." In Lamarckian theory, animals became more diverse as each creature strove toward its own "perfection," hence the enormous variety of living things on earth. Man is the most complex life form, therefore the most perfect, and is even now evolving.

In Lamarck's view, the evolution of life depends on variation and the accumulation of small, gradual changes. These are also at the center of Darwin's theory of evolution, yet Darwin wrote that Lamarck's ideas were "veritable rubbish." Darwinian evolution is driven by genetic variation combined with natural selection--the process whereby some variations give their bearers better reproductive success in a given environment than other organisms have.1 Lamarckian evolution, on the other hand, depends on the inheritance of acquired characteristics. Giraffes, for example, got their long necks by stretching to eat leaves from tall trees, and stretched necks were inherited by their offspring, though Lamarck did not explain how this might be possible.

When the molecular structure of DNA was discovered in 1953, it became dogma in the teaching of biology that DNA and its coded information could not be altered in any way by the environment or a person's way of life. The environment, it was known, could stimulate the expression of a gene. Having a light shone in one's eyes or suffering pain, for instance, stimulates the activity of neurons and in doing so changes the activity of genes those neurons contain, producing instructions for making proteins or other molecules that play a central part in our bodies.

The structure of the DNA neighboring the gene provides a list of instructions--a gene program--that determines under what circumstances the gene is expressed. And it was held that these instructions could not be altered by the environment. Only mutations, which are errors introduced at random, could change the instructions or the information encoded in the gene itself and drive evolution through natural selection. Scientists discredited any Lamarckian claims that the environment can make lasting, perhaps heritable alterations in gene structure or function.

But new ideas closely related to Lamarck's eighteenth-century views have become central to our understanding of genetics. [...]

Until the mid-1970s, no one suspected that the way in which the DNA was "read" could be altered by environmental factors, or that the nervous systems of people who grew up in stress-free environments would develop differently from those of people who did not. One's development, it was thought, was guided only by one's genetic makeup. As a result of epigenesis, a child deprived of nourishment may continue to crave and consume large amounts of food as an adult, even when he or she is being properly nourished, leading to obesity and diabetes. A child who loses a parent or is neglected or abused may have a genetic basis for experiencing anxiety and depression and possibly schizophrenia. Formerly, it had been widely believed that Darwinian evolutionary mechanisms--variation and natural selection--were the only means for introducing such long-lasting changes in brain function, a process that took place over generations. We now know that epigenetic mechanisms can do so as well, within the lifetime of a single person.

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