Epigenetics provides explanation of fearful conservatives who cling to the 'tough guy' charicature

[Bill USA]

... as a way of keeping all those 'scary' people from hurting them.

Researchers found that mice raised by inattentive mothers, or exposed to bullying by larger more aggressive mice (cf. insecure fathers who like to bully their children), were less able to cope with stress when mature, while those with attentive mothers grew up to be "calm and brave".   Mice raised by inattentive mothers showed greater methylation of genes regulating glococorticoid receptors which resulted in the mice not being able to handle stress as well as those raised by more attentive mothers (or not subjected to bullying when young).

Interesting stuff.

http://discovermagazine.com/2013/may/13-grandmas-experiences-leave-epigenetic-mark-on-your-genes

According to the new insights of behavioral epigenetics, traumatic experiences in our past, or in our recent ancestors’ past, leave molecular scars adhering to our DNA...

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With the assistance of postdoctoral researchers, they began by selecting mother rats who were either highly attentive or highly inattentive. Once a pup had grown up into adulthood, the team examined its hippocampus, a brain region essential for regulating the stress response. In the pups of inattentive mothers, they found that genes regulating the production of glucocorticoid receptors, which regulate sensitivity to stress hormones, were highly methylated; in the pups of conscientious moms, the genes for the glucocorticoid receptors were rarely methylated.

Methylation just gums up the works. So the less the better when it comes to transcribing the affected gene. In this case, methylation associated with miserable mothering prevented the normal number of glucocorticoid receptors from being transcribed in the baby’s hippocampus. And so for want of sufficient glucocorticoid receptors, the rats grew up to be nervous wrecks.

To demonstrate that the effects were purely due to the mother’s behavior and not her genes, Meaney and colleagues performed a second experiment. They took rat pups born to inattentive mothers and gave them to attentive ones, and vice versa. As they predicted, the rats born to attentive mothers but raised by inattentive ones grew up to have low levels of glucocorticoid receptors in their hippocampus and behaved skittishly. Likewise, those born to bad mothers but raised by good ones grew up to be calm and brave and had high levels of glucocorticoid receptors.

(more)

[cprise]

1. Regarding the old debate: So a lot of it IS 'nurture'

A very important subject for the development of our society.

[Bill USA]

2. right. THey are finding that experiences & ones reaction to them (ie. gene expression 'on' or 'off')

can be passed down to the following generations. HOwever, it's important to note that it appears this is not something locked in concrete. Good experiences (e.g. attentive mothering) can apparently change the pattern of gene expression in a person (e.g. from one initially not so good for, let's say, handling stress, to one more favorable for handling stress). This is a very interesting field of research.