Your topic sounds a lot like a combination of cultural and physical anthropology with a twist of developmental psychology served up in a glass full of crushed ancient history (pardon the analogy but new years eve is still lingering in my psych). I like it ! Case in point. It is commonly known that people who have recently suffered a CVA (stroke) often have significent depression for one to three months post CVA. The reasons for this depression is not fully understood yet the prevalence borders close to 100%. Using a tribal/nomadic historic perspective (I hope you like the phrasing) it would seem to make sense in a practical way. If you were living in a tribal nomadic group in cemtral Europe in say, the eigth century, the tribe would not be able to remain in one spot for any length of time due to needs for food and the possibility of attack (same would apply to the North American Plains Indians pre European invasion). The person who suffered the CVA would probably have to be left behind with the hopes of reuniting with the tribe if and when he/she recovered. To escape detection by the "enemy" and to actually improve one's possibility of survival wouldn't a depressed state be appropiate (flat affect, reduced animation, isolation, etc.). Iam suggesting that post CVA depression is a vestige , a throw back if you will, to a time when it served as a very valuable survival function..............If this type of connection is what you are looking please give me some feedback. I have very similar theories , msotly considered radical, on other dispositions such as: Downs Syndrome, MR, Mania, and other so called maladies of our modern world. My motto has always been "when modern science fails and instincts do not explain, take an historical perspective". I was an Historian in High School. ..........................Ed Riemann