This article is interesting though hardly surprising: Can PTSD Become Hereditary?. We can pass on to future generations the psychiatric problems we develop during our lifetimes.
To simplify a lot:
Our genes carry out some very important tasks for the organism of which they are part, such as providing active templates — tiny assembly plants — for proteins. Those genes are not some sort of unalterable instructions given by a god of evolution; they are not somehow shaped over long periods of time and unalterable over short periods of time. At the very least, the activity level, say from none to low to very high, can be set by the organism as it responds to its environments.
To simplify just as much:
Each generation of men then has to respond to its environments with given resources, including the starting-point of their genome inherited from their family lines and set to some levels of activity in the womb. Neurochemical balance and proper neuro-anatomical development can be re-established but it may take a few generations of stable, well-behaved environments.
Let’s consider a society of peaceful and prosperous farmers and fishermen and traders in Scandanavia. Let them suffer through a few generations of truly harsh weather, a Little Ice Age or something similar. A society of ruthless Vikings emerges. Reading a little bit into the research into the effects of climate change conducted by the late Reid Bryson (an opponent of Global Anthropogenic Climate Change theories for what that’s worth), we can conjecture that a promising young civilization, that of the so-called mounds-building Amerinds of the Mississippi river valleys, was destroyed by adverse climate events. The descendants of that demolished civilization were nomads with minds and bodies well-adapted to a pre-civilized life. I’d argue, only on general principle, that the changes to the bodies of Vikings and Mississippi Valley Amerinds were deep and lasting, lasting for some number of generations. I’d argue that way partly because that makes more sense of history and even the biographies of friends and acquaintances, than does the idea that each of us comes into our life clean of any contamination or blessings from what happened to parents and grandparents. Sins are visited upon the children despite the claims of shallow-minded theologians and philosophers and social-reformers, men and women who know little of history and science and haven’t thought clearly about what they do know.
This isn’t an endorsement of a strict determinism or pagan fatalism but I am claiming we should look at our own recent ancestors and see what their environments were like and how they responded to them. Then look at your own environments, your schooling and your upbringing — or not — in some faith, your social climate and economic incentives and opportunities, your political possibilities or at least those presented to you, your general culture. To a certain extent, probably a large extent, this can allow you to see yourself a little more objectively and a little more clearly. If you know a little history of the human race and a little more of your own family line’s history (such as Irish Gaelic or Chinese Han), if you know a little bit about the brain sciences and biological evolution, a little bit about modern technology and about its possibilities and dangers, a little bit about the nature of spacetime and matter and energy, a little bit about the possibilities of human thought raised by modern mathematics, then you know a lot that can help you see yourself more objectively and more clearly. I’m not saying this is the ‘real you’, but I am saying it allows you to see yourself in many of your aspects. It’s a modern liberal education in a manner of speaking, one that ideally does draw upon a rich knowledge of the old liberal arts but also upon modern empirical knowledge.
We are shaped by a variety of factors and we have at best partial control over many of those factors but we have no control without self-awareness. In particular, to exercise moral freedom we need good understanding of the ways in which we’ve been shaped and constrained by factors inherited from our grandparents or even from those apish ancestors who lived tens of thousands of years ago. Our freedom to a large extent is that of being able to reshape ourselves and to redirect our movements into the future, gradually and slowly. Our freedom isn’t that of a free-will without any sort of inertial constraints. Our freedom doesn’t even lie in the present so important to the fans of free-will. Our freedom lies in the future, or — more precisely — it lies in our movements into that future, our responses to our environments, which responses will shape our future selves. We’re organisms and we grow into freedom by growing toward a chosen state.