An age old question, that drives so much human energy to explore and understand. From religion, to work, to family, to friends, to pleasure, to exploration, to discovery, to ambition... much of our lives are spent in search of a meaning for life itself. Is there a reason behind our being?
The purpose of life is survivalShow moreShow less
"Survival of the fittest" is a common phrase in the biology field. If humans are not intent on their survival, they will go extinct. Similar to other species, humans eat, drink, and avoid danger their entire lives to stay alive. People spend their days making sure they survive to live another day; that is the sole purpose of life.
All life forms on earth have had to evolve and modify their DNA in order to survive, a fact which is indicative of the desire of life to sustain itself. Therefore, the purpose of life is more primal, and species are entirely concerned about ensuring they remain competitive in the ecosystem.
Life is a competition between species to secure as much food, safety and space etc. for their sustenance in a never-ending quest for survival and longevity. The way this plays out is by a random process theorised by the English naturalist Charles Darwin and known as natural selection. Natural selection demonstrates that the survival of organisms is based on the inheritance of small, favourable genetic traits that allow organisms to adapt to environmental changes and outcompete other organisms for the resources needed to survive. 
Natural selection suggests that the purpose of life, from a scientific perspective, is for species to continue their existence in a hostile environment by gaining traits that allow them to survive. The randomness of the process also means that the purpose of life cannot be some great, existential question because that would assume that humans and all other life forms are significant and can change the course of nature. Given their powerlessness in the greater scheme of things, the most species can do is avoid overtly dangerous situations - hence the instinctual drive to avoid or flee from predators, for example, such that life forms increase their chances of survival.
Conversely, extinct species are nature's experiments in the process of producing "fitter" organisms. Their dying out is a further reason why life is about survival as there is no life if organisms cannot ensure their survival.
Life cannot be about maximising the chances of survival for any given organism or species because evolution has led to the creation of intellectual life. Bacteria and fungi are examples of primitive life forms which are able to survive but lack any high order cognitive ability, indicative that there has to be a greater purpose to a life beyond just making it from one day to the next. Otherwise, nature and the evolutionary process would not have led to humans and other species who are able to rationalise their existence and experience complex emotions. Both traits do not enhance our chances of survival but instead make life more complex and less primal.
There is no great power or deity with a plan for the lives of people, everything is merely a random series of events. 
Life only exists if the organism can survive threats and hostile environments