Evolution is now accepted as a fact in biology, but debate continues about details of the evolutionary mechanism. The conventionally accepted mechanism is the theory of evolution by natural selection, proposed jointly by Charles Darwin and Alfred Russell Wallace in 1858.
Immediately prior to Darwin and Wallace, a different mechanism was proposed by the eminent French scientist, Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (17441829). In the early 20th century, Lamarck's ideas were resurrected in Russia by the agronomist Trofim Denisovich Lysenko (18891976). This had a disastrous effect on the development of genetics, biology and agriculture.
Although born into an aristocratic family, Lamarck was poor. He studied medicine as a young man, but soon turned to botany and wrote a popular book on plant identification. At 37 he was appointed Botanist to the King of France. He turned to zoology and published two major works - Zoological Philosophy (1809) and Histoire naturelle des animaux sans vertebre (1815).
It was becoming increasingly evident to biologists of Lamarck's time that life had gradually evolved over the long history of our planet. Geologists had demonstrated stratified layers of rocks in the earth's crust and palaeontologists identified fossilised organisms in these layers, with simpler forms generally occurring in deeper (older) layers. In successive layers, sequences of animals could be seen, with later ones showing resemblances to predecessors. The idea grew that modern life developed from earlier life by gradual change - evolution. Religion was very strong and many scientists accepted the creation account in Genesis, which states that all species of life were created separately by God in their present forms.
Other evidence pointing to evolution was supplied by study of body structure. When the structures of animals with backbones were compared it was seen that all, despite often grossly dissimilar outer appearances, differed basically only in the size and shape of different parts, but did not have completely different parts. It was also noted that vestigial structures, i.e. structures no longer serving a purpose, were common. For example, humans have a vestigial tail - the coccyx. All of this suggested gradual evolution from common ancestry. But what was the mechanism?
Lamarck accepted the idea of evolution and determined to explain the mechanism. He proposed in Zoological Philosophy that needs imposed on animals by the environment produced changes, even new organs, in the animals' bodies, and these environmentally-induced changes were then inherited by offspring. The classic example of "Lamarckism" is the giraffe's long neck. Lamarck would say giraffes originally stretched their necks to reach the leaves on tall tree-tops and the long necks were then passed on to offspring.
Lamarck's proposal that acquired characteristics are heritable was never widely accepted, and was quickly supplanted by Darwin's and Wallace's proposal on natural selection. We now know for sure that characteristics acquired by an animal during its lifetime are not heritable and we understand the reason. Genetics information passed from generation to generation is encoded in DNA. The DNA code we receive from our parents is not affected by our personal life histories, although our bodies are affected, and the code is passed on unaltered to offspring. So, for example, if my physical build is naturally slight, but I deliberately pursue body-building exercises and grow a physique like Arnold Schwarzenegger, I will still pass on my genes for a slight physique to my children.
The biologist Julian Huxley (1887-1975) made a telling comment on the idea of the inheritance of acquired characteristics - "If this theory is correct it would follow that all Jewish boys would be born without foreskins."
Although Lamarck got the mechanism of evolution wrong, he was a good scientist and made many notable contributions, e.g. he first made the essential distinction between vertebrates and invertebrates. He also coined the term "biology". He died in poverty, and mostly forgotten, in Paris in 1829.
Lysenko worked in the Genetics Institute at Odessa in the early 1930s, a time of crisis in Russian agriculture. He had convinced himself that characteristics acquired during the lifetime of a plant could be passed on to offspring. Lysenko proposed that he could produce a great increase in crop yields by developing new strains of wheat. The authorities welcomed this idea even though it was scientific nonsense.
It suited communist thinking to believe that the nature of life could be moulded by the environment. If the proper environment could improve the genetic constitution of wheat, then surely an optimum political, economic and social system would produce the "new man".
Stalin strongly backed Lysenko, who became a hero. Belief in conventional genetics was now interpreted as disloyalty to the state. Some scientists protested and lost their jobs. Nickolai Vavilov, director of the Institute of Genetics of the USSR Academy of Science, was sent to a concentration camp. Lysenko replaced him and remained at the top of Soviet biology until the mid-1960s. Soviet genetic research and teaching were badly damaged during this time. Lysenko's ideas did as much damage to Soviet agriculture as to Soviet biology.
Lamarck proposed an idea that was incorrect but honestly held. It didn't pass the test of observation and experiment and was quickly rejected. Lysenko's ideas, although palpably wrong when first proposed, were promoted by political ideology and survived for 30 yeas to do enormous damage in the USSR. Mistaken ideas do no harm in science and are quickly rejected. However, when either political or religious ideology command influence in science, truth can suffer for extended periods.
(William Reville is a senior lecturer in bio- chemistry and director of microscopy at UCC.)
In last week's article on Francis Galton I wrongly attributed the term "Galtonism" to early popular descriptions of colour blindness. The actual term used was "Daltonism", after John Dalton (1766-1844) one of the first scientists to note and record colour blindness. Dalton was the famous British chemist who proposed the theory of atoms.