The researchers studied the number and kind of microRNAs expressed by adult mice exposed to traumatic conditions in early life and compared them with non-traumatized mice. They discovered that traumatic stress alters the amount of several microRNAs in the blood, brain and sperm — while some microRNAs were produced in excess, others were lower than in the corresponding tissues or cells of control animals. These alterations resulted in misregulation of cellular processes normally controlled by these microRNAs.
After traumatic experiences, the mice behaved markedly differently: they partly lost their natural aversion to open spaces and bright light and had depressive-like behaviours. These behavioural symptoms were also transferred to the next generation via sperm, even though the offspring were not exposed to any traumatic stress themselves.
However, certain questions remain open, such as how the dysregulation in short RNAs comes about. “Most likely, it is part of a chain of events that begins with the body producing too much stress hormones.
The environment leaves traces on the brain, on organs and also on gametes. Through gametes, these traces can be passed to the next generation.”
Given that most of history for most people over the last 10,000 years has been pretty grim, one wonders how much the stresses of war, poverty, disease, slavery etc have determined what we casually call ‘human nature’.
Instead of asking what would life be without all the Sturm und Drang, maybe we should ask what humans would be without centuries of it.