Lamarck's Evolution Theory Revival
In Some Cases Adaptation Seems to be Deliberate Rather Than Random
Sep 5, 2009
Lamarck was the first to present an evolutionary theory although no-one believed him. According to Lamarck, organisms are continuously being more complex by actively adapting to their environment in contrast to Darwin's dogma stating that changes were random and selection has a role in keeping the fittest individual. Throughout the past years, researches supporting Lamarck's theory are starting to accumulate. It seems that adaptation can be deliberate and is probably mediated by epigenetic changes.
Two Explanations for Adaptation
Two hundred years ago and fifty years before Darwin published his revolutionary book the Origin of Species, Jean Baptiste Lamarck published a book names Philosophie Zoologique. In his book, Lamarck set the foundations of his evolutionary theory. According to the theory all species were descended from a spontaneously created common ancestor and were sorted into species by adapting to their environment.
Adaptation according to Lamarck is a result of using an organ extensively. An organism that is not fully adapted to its surrounding will use some organ in a way that will change it – strengthen or weaken it; this use or disuse will make the organ larger and more suitable or smaller and weaker. The changes made by an individual will be transferred to its offspring making the changes accumulate throughout the generations. According to Lamarck it is possible that if a parent works out the child will have increased muscle size for an instance.
The model of Darwin is quite different. According to this model, the physiological changes will appears randomly in an individual and an individual best fitted to its environment will have the highest chance of survival and will eventually take over the population. Darwin introduced the power of selection as an important part of the evolutionary process.
Lamarck's Model is Reviving
Recent observations support the hypothesis that adaptation is active instead of random. The main concept that Lamarck's opponents disagree on is the ability of an individual to endow an acquired phenotype to its offspring. An example frequently mocked at is that a giraffe reaching out for leaves at the top of the tree will have a young with a longer neck. Scientific papers published lately suggest that the concept is not fully incorrect.
A famous example of adaptive changes transferred from a parent to its offspring is found in the immune system. The adaptive immune system has the ability to generate antibodies against newly introduced foreign molecules. It was found out that once an antibody was developed it can be assimilated in the germ line and transferred to the next generation. This mechanism is a typical example of Lamarckian inheritance.
In 1999 a group of researchers from Australia, Scotland and the United States showed that genetically identical mice had different coat color in a paper called 'Epigenetic inheritance at the agouti locus in the mouse' published in 1999(23) issue of the magazine Nature genetics. The coat ranged from yellow to mottled and the color of the newborn's coat was highly influenced by that of the mother but not the father's. The observation demonstrated that epigenetic changes can be inherited although this trait was not set or obtained by the mother.
The Dutch famine of 1944-1945 winter provides an example of an epigenetic change that was both acquired by the parent and inherited. Near the end of the Second World War, during the 1944-45 winter, there was a famine in the Netherlands. Children born after the hunger and exposed to it during pregnancy were found to have more cardiovascular diseases and higher cholesterol levels.
A group of women affected by the hunger was used to test if the phenotype can be inherited to the next generation or not. When the grandchildren of the women that were pregnant during the hunger were checked they were found to be in poor health relative to children whose grandmothers didn't experience the hunger while being pregnant, however, not to the same extent as the first generation. The research, made by Painter RC et al. was published in 2008 in the BJOG: An International Journal of Obstetrics & Gynaecology, entitled 'Transgenerational effects of prenatal exposure to the Dutch famine on neonatal adiposity and health in later life'. This research shows that changes made by the mother can be transferred to her children.
Although the Lamarckian model of adaptation and evolution is not fully understood or established, several mechanisms can explain such a phenomenon. Epigenetic changes or different protein expression profiles rather than different DNA code can explain the variation in a population and these changes can be kept through generations. An individual adapting to some environment can transfer the changes it made to the germ-line and to its offspring by a partially known mechanisms. Although Lamarck's theory of evolution is not fully accepted some traits are set and inherited in a way that supports it.
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