First off, I would like to say good discussion...Really hit alot of the pertinant questions and information. I would like to add a bit myself...First off "Will" is incredibly important for evolution within humans...and a good chance even for animal evolution<though chasing down the evidence for that is a job>.
Will is important within humans for survival...you must have a will to survive. When your will to survive allows you to be victorious over your opponents you are able to pass on your DNA...Without will to live and survive you die...not always before you can pass on your genetic material...< Funny statement I heard once,"We aren't descended from the big burly guys fighting cave bears, we are descended from the smart quick little fellows who had the sense to runaway">
Now that is my case for Will being important to evolution<really natural selection than evolution>. One thing I read a while back was about heighth of people...and how that people were getting progressively shorter because of the big guys getting carted off to war and getting themselves killed, which ended up breeding men small. That trend ending after the advent of gunpowder when you didn't HAVE to be a big guy to shoot a gun and that being a big guy actually made you less fit for fighting because of the target you presented...true? I don't know...I do know that people used to be real short, but now are getting freaking huge compared to our ancestors...even though that is quite often attributed to malnutrition of early peoples. I do agree totally with how natural selection works...and you can see it in many peoples.
As to people from military families becoming military themselves...I would say that has just as much to do with the family structure as it does with genetics. Also that coming from a military family doesn't make you any more fit to be in the military than someone who wasn't. IN FACT, In my experience those from military families are less fit because they have a preconcieved notion of what they think battle is and how it should be done. West Point officers who are from West Point graduate families quite often are complete boneheads that need to be digging latrines as compared to Officers who came from nothing...is really all in how you manipulate the statistics.