A fascinating article at Science Daily today: Epigenetics: DNA Isn’t Everything.
A certain laboratory strain of the fruit fly Drosophila melanogaster has white eyes. If the surrounding temperature of the embryos, which are normally nurtured at 25 degrees Celsius, is briefly raised to 37 degrees Celsius, the flies later hatch with red eyes. If these flies are again crossed, the following generations are partly red-eyed – without further temperature treatment – even though only white-eyed flies are expected according to the rules of genetics.
These two flies have the same eye color genes
And not just them: other species like the agouti (certain rodent) also have shown to be able to transmit epigenetic modifications to the next generations like if these were normal genetic traits.
This means that enviromental influences can have very long lasting effects, overruling the genetic fundamentals. Genes are not themselves modified in these epigenetic processes, just activated or deactivated, the same that your liver cells are so they can only be liver cells and not, say, neurones or muscular cells. The fascinating discovery is that such transformations, when they happen at embryonic level, can become permanent and transmitted to further generations without known limit.
I wonder how many of the human phenotypic traits that anthropometrists usually attribute to genes with no or limited evidence are in fact mere epigenetic "permanent" modifications because of this or that historical accident. It would be nice to know for sure.