What we are today is 3.8 billion years of evolution. A natural question arises, how is it 3.8 billion years when humans have been around for only 2 million?? Most people tend to forget that we didn't just drop from heaven 2 million years ago. Although humans have been a separate species just for 2 million years we had ancestors, who themselves had ancestors all the way back to beginning of life. So every living creature out there today, including ourselves are all 3.8 billion years of evolution.
Now that we have established that, lets look at what we have been taught over the past 3.8 billion years. In the past our survival was ensured by our native emotions. The emotional part of our brain commanded when to run and when to fight. Every aspect of our behavior was controlled by emotions. All that began to change a few thousand years ago, when humans developed the intelligence to form civilizations. The intelligent part of the brain (neocortex) has grown at a pace way faster than the emotional part of our brain (amygdala) could keep up. So the result is, we humans still follow our innate instincts and try to eliminate others to ensure our own survival. In the past this was done by throwing spears at the neighboring tribes, now it has evolved into a form called racism and nationalism, which all people are equally guilty of.
Humans are so caught up in eliminating each other that we forget, what we are fighting for on earth, is nothing compared to what is out there. Consider this, our entire solar system excluding the sun, forms less than 1% of the Sun's mass. Our sun itself is one of 10 raised to 22 stars (that we know of) out there. So that means if we distribute the stars in the known universe, equally among all the humans, every one gets more than a trillion stars!! That compared to the wealth and resources on earth, is infinite.
Instead of destroying each other what we need to do is to come together as humans and work towards colonizing the space. Once we start working together on the space colonization and fending off alien threats (which could be an exploding super nova or an aggressive alien species), we will realize that we are actually really short of people.