The role of methylation in affecting gene expression, however, may make evolution more Lamarckian in nature.
It reminds me of back when I was a kid. I took a population of tadpoles and put them in a tub. The remaining mud-puddle population quickly grew legs and hopped away as tiny toads as the mud puddle dried out. The tub population, however, just became fatter tadpoles, developing legs only very late. Somehow their growth was being affected by the availability of water. Pretty amazing stuff!:
As scientists came to better understand the function of methylation in altering gene expression, they realized that extreme environmental stress—the results of which had earlier seemed self-explanatory—could have additional biological effects on the organisms that suffered it. Experiments with laboratory animals have now shown that these outcomes are based on the transmission of acquired changes in genetic function. Childhood abuse, trauma, famine, and ethnic prejudice may, it turns out, have long-term consequences for the functioning of our genes.
These effects arise from a newly recognized genetic mechanism called epigenesis, which enables the environment to make long-lasting changes in the way genes are expressed. Epigenesis does not change the information coded in the genes or a person’s genetic makeup—the genes themselves are not affected—but instead alters the manner in which they are “read” by blocking access to certain genes and preventing their expression. This mechanism can be the hidden cause of our feelings of depression, anxiety, or paranoia. What is perhaps most surprising of all, this alteration could, in some cases, be passed on to future generations who have never directly experienced the stresses that caused their forebears’ depression or ill health.
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