Anyone who would doubt the significance of humanity needs only to look upon the history of this world, wherein our species has displayed an absurdly greater mastery of our environment and potential to change the image of an entire planet than any which came before us.
While there exists scientific evidence of our gradual divergence from other, less sophisticated organisms through the process of evolution, nonetheless, this is no reason to assume that our species is not special. The debate still exists between those who steadfastly believe that the presence of our species is merely a fluke in the ultimate scheme of the universe and that we are destined to merely fade into the void, with our only testament being a background of cosmic noise and space probes which no other sentient species will ever discover, and those who believe that we were placed here by a being on a higher plane of existence, with a purpose of being a sort of "master species" for this planet, with dominance over all lesser species, and in some systems of belief, over eachother as well; until we have reached a point at which we are prepared to join with whatever entity placed us here. Our unique role in relation to other species of our world is such that at this time, there are compelling arguments in the favor of both sides of this eternal debate of beliefs. As my beliefs compel me to take a more objective view of the world around me, I have, over the years, come to a different conclusion altogether.
Life is self-purposed. The primal desire to exist and thrive, the force of evolution, and our free will and intuitive curiosity about the universe are all interconnected. Life itself is a tenacious survivor; if environmental conditions are such that life begins to struggle, as long as there is a will to continue to exist and the changes are gradual enough, life will nearly always find a way to adapt and survive. Scientists throughout history have witnessed this self-preservation instinct in even the lowest forms of life; however, the mysteries of life are such that even the most intensive of scientific research cannot pinpoint the exact cause of this basic urge. To say that it is merely a chemical response system is also debatable, as there have been found microbial lifeforms which never advanced beyond that point, whose chemical composition are vastly different from those of other species, which nonetheless still exhibit the same self-preservation instinct as any other organism of that level of complexity.
That's right, as a species we have managed to split the atom, even collided sub-atomic particles to discover ever smaller objects of matter than current theory holds should even be viably possible to exist within the understanding of physics within this plane of existence... and yet, we still cannot find the source of our desire to exist.
If you are of an open mind, allow me to share my personal theories toward this subject.
Firstly, a common theme throughout nearly all religions is the mystery of the entity which created us. Some common statements are that (1) we were created in God's image, (2) that no man has ever seen the true face of God, and (3) that God exists in all of us. We should keep in mind that at the core of nearly every religious conflict throughout our history has been the disagreement over the exact form of our creator... but this directly conflicts with the second point listed above. How can any side ultimately be proven right if they cannot agree on what should be an inherent truth at the core of their own beliefs? In addition, with our current understanding of the nature of existence, is it not fair to assume that if something has a finite, perceivable form, that it therefore cannot be omnipresent? Or, by assuming that the entity we all have come to know as God even has a finite and perceivable form, are we not attempting to suggest that there is a limitation to a being which is understood to be omnipotent? The most simple conclusion in all of these questions is that what we refer to as God simply has no specific form which we can understand, and presents itself within our physical realm as the desire to exist... and that Yahweh, Allah, and all others are just titles which various human cultures have come up with as a means to identify the exact same thing. In other words, while one could argue that, as we are currently the most advanced species on the planet, that we are the closest to God's "image," there is still the issue that most cultures' understanding of God is based off of their own cultures' influence; that, in essence, we have created many Gods in our own image.
Essentially, the conclusion which I have come to is that God is present within our physical realm as the desire for continued existence, which in turn influences the direction of evolution as a means of achieving this goal. It is an influence on living beings which transcends the physical realm, which gives rise to what we know as souls and our ability to make decisions out of our own unique perspectives regardless of cultural influence. There should be no reason for the concepts of "free will" and "faith in a higher power" to be mutually exclusive as many people seem to believe; rather, can it not be said that these concepts can not only coexist, but are even one and the same? Perhaps the scientific evidence of humanity's rapid development from lesser species, the tales of our sudden creationism, and even our desire to explore and expand our frontiers are all, in the end, different means of expressing the exact same ideal. Our purpose in existence is, above all else, to continue to exist. This is a desire that is inherent in all living things, which transcends our physical being, even after the physical body has long since been extinguished.