So I propose that man searches for meaning only because he can. It's entirely unnecessary to be a happy and healthy creature on Earth. Most social animals find meaning in belonging to their tribe. Since we are social apes, could it be that we seek in the idea of God, that which we are missing in our society? Monotheism arose along with civilization and cities. Could it be that our connection with nature is what gave us meaning in the past?
After reading my last post, let's then question why we have such a desire for purpose. This is answered simply enough:
Notice, as members already have, that animals don't search for meaning in their lives. This is because they aren't intellectually developed as we are, if we were to somehow inject a cat with a dose of super intelligence, then it'd be a safe bet to see questions of mathematics, philosophy, and purpose emerging. If that's to rhetorical of a scenario, recognize that we witness this development everywhere, even in our own species. Babies don't understand math, philosophy, or have any sense of purpose whatsoever. It's not to say that the potential isn't there, but that they just haven't passed that milestone yet.
So let's clairvoyantly travel back to the dawn of humanity's creativity; whether it was the spear, cup, wheel, fire, or whatever, this first manifestation of creativity was made with a specific purpose in mind. Thank goodness this happened, today we are surrounded by millions of inventions and tools, all with specific purposes in mind. This kind of development breeds an odd type of thinking, however. Because we are so immersed in an exponentially increasing purpose-oriented society, we naturally turn introspectively (once again, a product of evolved intelligence) and are able to linguistically and philosophically engineer the question around ourselves; why are
we here? This question amplifies organization and growth, as we can greatly see from our progress as a species. It allows us to excel as the dominant species, so there's really no mystery as to why we have such a strong gravity towards a purpose for our own existence.
Note however that, as stated above, just because we can form this question doesn't mean it has an answer.