It is a widely held perspective that humans are relatively insignificant creatures in the universe who are lucky passengers on a "Spaceship Earth" which has a uniquely hospitable biosphere that acts as our life support system.

David Deutsch refers to this anti-anthropocentric attitude as the Principle of Mediocrity.  This idea that there is nothing cosmically significant about humans has its basis in an error prone way of thinking known as parochialism.  Parochialism is about mistaking appearances for reality, such as assuming that local regularities in phenomena are universal laws.  Most humans navigate the world through their own perspectives and develop rules of thumb that they mistake for greater universal knowledge.  For centuries, humans mistook the rotation of the night sky as implying that the stars are moving and the planet is fixed.

However, when we step away from parochial views about humans, we find that they are indeed significant.  Unlike every other organism which relies on evolution to create the genetic knowledge that enables the survival of its genes, humans are able to create explanatory knowledge and bypass the limitations that the evolutionary process puts on other species.  All other organisms are inherently restrained to functioning within a certain range of environments that are hospitable to them, while humans can actually transform their environment to make it hospitable.   
 
Evolution, left to its own devices, is unlikely to ever move an earthbound animal into orbit where it lives outside the biosphere, but humans have been living there continuously on the International Space Station for years.

Most life on the planet is a type of constructor, which is basically a system (or device) that is capable of causing other objects to undergo transformations without undergoing any net change itself.  Evolutionary knowledge held in the genetic code of lifeforms enables them to act as constructors that convert raw materials of a fixed type into more of the same type of organisms.  

But humans are universal constructors because they can cause any raw materials to undergo any physically possible transformation, given that they possess the right knowledge, namely, explanatory knowledge, that they can create in their minds.

This leads to the profound implication that humans are indeed cosmically significant.

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