We watched "The Ghost in Your Genes" - a Horizon documentary last night and it's startling how the impact of environmental factors can change the way your genes behave. The most enlightening and perhaps frightening part of this discovery is that the lives of previous generations actually impact on our own in a very specific way.
Check the BBC's own page about the program.
"Epigenetics adds a whole new layer to genes beyond the DNA. It proposes a control system of 'switches' that turn genes on or off – and suggests that things people experience, like nutrition and stress, can control these switches and cause heritable effects in humans."
I am now on the hunt for some good books on the topic.