A study on rats has shown that exposure to certain chemicals during pregnancy affects not only the fetus, but generations to come. In the news report: The work implicates a class of chemicals found in certain plastics, as well as one found in jet fuel.

'The idea of "epigenetics" - that parents do not just pass their genes to their children, but subtle differences in the way those genes operate - is one of the fastest growing areas of scientific study. Rats exposed to phthalates had offspring with higher rates of kidney and prostate disease, and their great-grandchildren had more disease of the testicles, ovaries and obesity'.
Maybe an overweight person can blame their grandparents for their condition.
Dr Skinner said: "Your great-grandmother's exposures during pregnancy may cause disease in you, while you had no exposure. This is the first study to show the epigenetic transgenerational inheritance of disease such as obesity." The study stresses that the tests were in no way conclusive and would not be conducted on humans.
Can we justify experimentation on animals? We know rats are highly intelligent animals. Some people even keep them as pets, like Ben. I find the whole subject of causing harm to animals repugnant. Will humankind ever stop their interference?
Is it worthwhile for a few creatures to suffer to benefit others?
The same case could be argued for servicemen who suffer or die during war.