If people suddenly came to the intellectual conclusion that life had no meaning, or that we will never know the meaning of life, very few would throw up their hands in futility and stop living. There's no question that the answer to the question of life is heavily dependent on one's personal and religious beliefs. There is little point debating over one's personal beliefs, since beliefs do not come from empirical analysis, but from faith. Humans are unique in that we can create our own purpose in life. Purpose is, of course, similar to meaning, except that it is little less abstract.
Purpose is a part of meaning, but so is goals, intent, and inner significance.
Goals, in fact, make up purpose. Humans still fill that role in the web of life, but through the creation of civilization, humans have outgrown that role as our sole purpose. We used our excess brain capacity to achieve our goals of survival by broadening our goals. Instead of merely pursuing the goal of hunting with our hands and feet, we broadened our goals to creating weapons to hunt with as well hunting. Instead of just stockpiling food to survive during the lean periods, we also stockpiled to increase our status in our clan.