Beyond the blueprint
May 5th 2009, 10:47
More than 50 years before Darwin wrote On the Origin of Species, French zoologist Jean-Baptiste Lamarck wrote Les Recherches sur L'Organisation des Corps Vivants, the first book to set out a coherent and well-developed theory of evolution.
Where Lamarck differed from Darwin was in his belief that the environment, rather than genetic coding, was responsible for changes in animals, and that these changes could be inherited.
Lamarck-who has been ridiculed for generations-has now been vindicated by recent studies showing that environmental influences cause changes in organisms that may even persist through generations. Scientists are only now beginning to understand that it is outside influences filtering through the cellular membrane that control the expression of most genes and, in turn, affects the chemical coating (methylation) of the DNA double helix, which is exquisitely sensitive to the environment, particularly during the early stages of life. In our cover story this month (May 2009), WDDTY Deputy Editor Joanna Evans has uncovered a wealth of evidence showing that environmental exposure to pollutants-pesticides, plastics, even tobacco smoke-may be responsible for widespread obesity. The most extraordinary revelation is that the damage mostly occurs through prenatal exposure.
This is especially worrying as many 'epigenetic' changes persist through many generations. In times of famine, for example, populations exposed to famine prenatally have lower birth weights and higher-than-normal rates of degenerative diseases such as diabetes, coronary heart disease and cancer. Yet, even when they received adequate nutrition, those whose mothers had been starved produced smaller-than-normal children and grandchildren.
The environmental conditions affected at least two generations down the line (Paediatr Perinat Epidemiol, 1992; 6: 240-5 3). This suggests that those who are overweight due to chemical overload as babies will produce several generations of fat offspring.
The only note of optimism is the evidence that a good environment can also correct illness.
A mouse study by La r ry Feig and his colleagues at Tufts University looked at whether or not a stimulating environment could override knocked-out genes (Ras-GRF), without which the animals can neither learn nor remember. Put these mice in an unpleasant situation they've already experienced, provide the stimulus that should trigger the unhappy memory- and they won't have the foggiest recollection of it.
But, when the researchers exposed such 15-day-old mice to the equivalent of a indoor theme park-a large cage with play tubes, cardboard boxes, a running wheel, and toys and nesting material-that was changed or rearranged every other day. After two weeks, the mice developed a compensatory new protein pathway that helped their long-term memory and learning. Even though they were still missing the gene, a stimulating environment, in effect, turned it back on. The mice showed normal memory and fear conditioning.
Feig then took this one stage further and examined what happened to their offspring, which were given the usual environment rather than the theme park. Astonishingly, these offspring showed every evidence of normal memory and learning ability even though they had inherited the knocked-out gene and had experienced no additional stimulation.
In fact, the environmental effect of their ancestors again overrode their genetic destiny-this time to positive effect.
This means that perhaps it's not too late for us to begin cleaning up our environment.
Certainly, we owe it to our great-grandchildren.
This latest blog introduces the main story in the May 2009 issue of 'What Doctors Don't Tell You'. It is available only to subscribers. To subscribe, please follow this link: