To be an organism is, inescapably, to be challenged.
As long as one is alive, the “struggle for existence” is an imperative condition lasting until one reverts to inert matter.
Before that collapse, the essence of life is to succeed in meeting all the various, ceaseless challenges that threaten oblivion. Thus organisms are by nature strugglers and fighters, no matter how pacific or serene some may seem. While there appears to be an implicit imperative in the cosmos that births life from non-life, nonetheless, once animation emerges from inorganism, its continuing existence is challenged.
Although we are the most complex and sophisticated species we know, we humans are no less challenged than any other creature and must learn to struggle successfully or die. It is therefore no surprise that we are combative, that we are prone to contending and fighting so as to secure and protect the means of our survival and our flourishing. To expect us to be peaceable and loving is to thwart our essential combative instincts for security.
Only when human society has developed secure means to protect its members may individuals relax enough to attend to more “humane” enterprises transcending the fundamental need for safety. Even so, we remain “wired” for challenge, contention, and combat; and we’re likely to lash out to protect our egos, our turf, or whatever contributes to our sense of well-being.
Therefore, the road to sagacity and sainthood is rugged and steep, and few find the Way of the Buddha or Jesus: the serenity, loving-kindness and inner security that surpasses the instinct of self-preservation.