a disclaimer: i am not advocating violence, but merely making an observation, though highly objectionable and contentious. so kindly bear this in mind through the following paras.
first, what do i mean when i say 'integral' to human nature? it is, i must admit, not a very precise idea (though not altogether imprecise either), but what i wish to say is that something which is integral to human nature will imply that that aspect has been ingrained into our DNA during the process of evolution. something which is heritable and variable across humanity and which thus passes and changes from generation to generation. something like... well, our ability to retain memory, fight for survival, search for food, take care of our babies, etcetera. you are thinking that there are many exceptions to the rule. i say, exceptions prove the rule. anyway, let us return to the main point at hand.
presumably, the neanderthal men had a larger exposure to violence and bloodshed (not only of fellow men but also of animals) than the present day homo erectus. this might be the stage where this primal habituation to violence got ingrained in us along with mating behaviour, care of the young and other things. however, in the current day and age, the average human is not exposed to violence anymore. (again there are exceptions of policemen, army-men, homicide and rape victims, terrorists etcetera but think of the population by and large and think of people, on an average. this might sound flimsy, i do not have statistics to support it, but i am sure if you take the trouble to disprove me on this count, you will end up correcting yourself.) nowadays, the only violence people see and hear about is in the papers, on the telly and the radio, and in celluloid. so, the fact remains that the inbuilt faculties which enabled our species to get by thousands of years ago with maar-kaat and hinsa are, at the end of the day, being suppressed by societal norms and laws (and for good reason too, i don't need to emphasise on that).
what i want to drive home through the above discussion is that we humans, as a species on the whole, are sitting on a time bomb of violence - which can be unleashed if the conditions were suitable.
my argument is proven by the stanford prison experiment, where the subjects were removed from all societal norms (by creating an idea greater than society viz. the furthering of since and understanding) and let loose, in a manner of speaking. the subjects who were given totalitarian power within the domain of the experiment (on the condition that there will never be any punishment for them) metamorphosed from an average person into a savage, psychotic (although note here, only by humanities current standards) and nearly insane. this is because, i believe, they found that violence was satisfying, satiating and something that was 'very them'.
of course i shall not overlook that there were others who metamorphosed into personae which let themselves be hurt and ostracised. where, then, is their violence? the answer to this is, it is not necessary to be the aggressor, the primary thing is that you are part of the violent act - it does not matter in what capacit exactly. being a part of the violent act at the very ground level is gratifying - that is my thesis, your precise qualitative role is simply incidental.
by gratifying i do not mean to say that it gives a perverse form of pleasure. no that is not my point, i am not here to glorify violence. the point is that violence, so inherent to us, on being suppressed, leads to dissatisfaction and discontent - and the 'gratification' i talk of is simply the removal of this discontent. look around, our entire generation is wallowing in shallowness, dissatisfaction, meaninglessness and the lot, but give them a revolution to rebel in, music to dance to and drown in, sports to strive forth in, and poof! all the ennui and meaninglessness vanish. this is because all these activities are substitutes for violence. so are the acts of sex and love. they imbibe in you an emotion level which so mischievously skirt around violently grey areas that it is not surprising they fill you with a 'thrill'and 'energy' so akin to the feelings of a valiant soldier on the battlefield.
if all this sounds utter crap to you, then think about this - had violence been harmful to Man, it would have been weeded out by evolution in the past 50000 years. since it is still a part of our society it shows that this is not possible. we have to learn to live with it.
again you might rebut that violence might not be heritable which sounds pretty logical, but i believe that it cannot be entirely environmental (read parental and societal influence) either.
keeping these in mind, the fundamental questions of war and peace resolve into a picture of disease of the human nature - violence. it is a disease we have to strive against, wage a war against - and rise above ourselves adhering to the principles of non-violence. i feel that sums up, in a nutshell, why we feel our lives to be inadequate and meaningless and what it is actually about.
so this what i conclude -
the primary needs of a man are not food, shelter, and clothing but food, shelter, and a third component which I cannot give a name, and which contains within its boundaries the acts of sex, communication and violence.