ABSTRACT
Curiosity regarding the environmental influence on heredity has existed for the past 200 years or so. Indeed, some believed that the environment acting over long periods of time could somehow change genes and specifically direct the course of evolution. One such was Lamarck (1744-1829), who believed that those parts of an organism that were used extensively to deal with the environment became larger and stronger, while those not used deteriorated. One example he cited was the giraffe stretching its neck to new lengths in pursuit of leaves to eat. He proposed that such modifications acquired during the lifetime of an organism were inherited by the offspring. The giraffe’s long neck, he argued, was the cumulative product of a great many generations of ancestors stretching higher and higher. However, there is no evidence to support the view that acquired characteristics can be inherited. Nevertheless, in the 1920s, Lysenko, who during the reign of Stalin was allowed to exercise absolute political control over Russian genetics, decreed that geneticists there should
accept the dogma of acquired characteristics. In particular, he was concerned with the effects of ‘vernalization’ in plants, which he believed could be inherited. He proposed that winter varieties of cereals could be genetically converted to spring or summer varieties by cold treatment. We now know that none of the genes involved were altered by the low-temperature treatment. Instead the prior cold treatment merely substituted for the natural chilling period of winter, which is a necessary requirement for stem elongation and flowering of these winter varieties. While it is now accepted that the environment cannot direct evolution, it is nevertheless clear that the activity of many genes can be profoundly influenced by environmental factors, including those that can alter the chemistry of DNA.
