There is probably no greater unknown aspect of human life than the "purpose of life". All living organisms begin life with a built in, hardwired purpose which drives them throughout their existence. We call this hardwired purpose "instinct". Except for humans all other organisms can avoid their purpose only by dying before their purpose is accomplished.
While humans are born with the same built in, hardwired purpose as all other living organisms, humans, through the gift of intelligence can forge their own purpose and override the hardwired purpose they are born with. With intelligence, normal humans can write their own destiny regardless of the circumstance into which they are born. History is replete with stories of humans, both male and female, who have risen from utter despair to great heights. The single common factor in all of these stories is that each of the people had, first and foremost, a set purpose toward which they directed all of primary efforts.
Moreover, because of the way human instincts are implemented in the human brain, humans can not only pick and choose between different purposes for their lives, at a young age humans are forced to choose a purpose to which they will devote their lives. The most successful humans are those who pick a life purpose that is moral and contributes to society's success. The least successful humans are those who are incapable or unwilling to commit their lives to any purpose. Unfortunately the latter includes the majority of the human race.
One of the first and most important things taught in Business 101 is that to be successful any enterprise must have a purpose and every function of the enterprise must be aimed at accomplishing that purpose. In the military the objective is the purpose of an army. The general does not say "go fight the enemy" which leaves the troops without any specific direction. Rather he says "your objective is to take hill 107 which provides both a direction and a purpose." No successful army ever moved without a specific purpose!
Without a fixed purpose human life is simply a hapless, aimless wandering from birth to death with no chance whatever of accomplishing anything which benefits anyone. Perhaps even worst than having no purpose is having the wrong purpose and wasting efforts and resources in this folly as the human race has been doing for at least 200,000 years.
There is a given (either by a Deity or acceptance by humanity through intelligence, free will, logic and self interest.) purpose to human life, the clue to which is written in stone across the mountains of Earth for all to read. Unfortunately, the knowledge required to decipher the writing has only been acquired within the last 192 years. Before then there was no possibility of humans discovering the true purpose of human life.
In 1819 Georges Cuvier was instrumental is starting the scientific field of paleontology which is the study of prehistoric life on Earth. The study of prehistoric life involves the study of fossils which are the petrified (turned to stone) remains of creatures and organisms long dead. This fossil record is a 3.2 billion year record of life on earth written in stone. Through this study scientist have concluded that for all the differences in size, shape, color, makeup and functioning of prehistoric organisms, all living creatures on Earth since the beginning of life have accomplished only one thing in common. That one common factor of all living organisms is the reproduction of their species. All of these trillions of creatures, living and dying over more than 3.2 billion years, learned nothing beyond what was needed to survive to propagate. They learned nothing because they did not have any capability to learn beyond what was needed to survive and propagate. Learning and abstract reasoning were not possible on Earth until the evolution of humans some 200,000 years ago.
It is not a stretch to say that because all these organisms did nothing except propagate that the purpose of all living organisms is to propagate. Some will nitpick that function and purpose are not the same thing, that a purpose implies a premeditated intention, an objective, a strategy to reach it and an awareness of the whole process in order to carry it out; where as the function can be the mere instinct and often a simple chemical reaction. The fact is that mere instinct and chemical reactions are in fact choices (premeditated intentions) which all organisms experience. The only difference between other lower evolved organisms and humans is that humans can choose to act or function differently from what their instincts and chemical reactions dictate. All organisms want to and do put most of their efforts into survival and propagation. Consider the lengths most organisms will go to avoid death and pain and to mate! Many creatures mature, mate and die immediately. Would you try to get between a female tiger in heat and a male tiger? Consider it this way… the premeditated intention, objective, and strategy are hardwired choices and desires which all organisms have but which cannot be avoided except by humans.
For one last example, consider the hammer. The hammer was invented to pound things with more force than the human hand could apply. The function of the hammer is to pound things and to pound things is also its purpose. It may of course have other uses, but it is folly to say that the purpose of the hammer is any different that its function (i.e. to pound things)! The hammer itself has no awareness of anything and therefore cannot have any premeditated intention, but that does not change the fact that the purpose of the hammer is the same as its function.
If we accept that propagation is the given purpose of life (given by God of course if you believe in God or by the Laws of Nature if you don't, it must have come from somewhere.), what does that mean for humans? First it means that humans have gotten it wrong for a long time and continue to do it wrong. If you took a poll of Earth citizens and ask "what is the Purpose of your life?" you will get primarily two different answers, sometimes both from the same person. Most will answer "To do God's will" or "my children." It turns out both answers are correct, the problem is that there are and have been approximately 2500 different versions of God's will, ranging from the requirement for human sacrifice to doing absolutely nothing except praying. There is not, nor has there ever been any verifiable communication between God and humans. If we examine the various "Words of God" handed down through the centuries it is obvious that the "Words" were either written by humans without any input from God, or God did communicate with the authors of the "Words" with the intension of confusing and causing pain and harm to humans. If God is a benign, loving Deity, there simply cannot be 2500 different correct versions of God's Words. There cannot even be two different correct versions of God's Word. To think otherwise requires that some kind of insanity be at play. Something cannot be both all black and all white at the same time.
This is the reason God allows so much evil to exist in our world. God simply does not interfere in the affairs of humans. For one thing God interfering in affairs of humanity would negate the immense gift of free will humans' posses. If humans are indeed endowed with free will then God must allow humans to do whatever they desire to do and all evidence strongly suggests that is indeed the case. Human free will is limited only by the Laws of Nature. Anything that does not violate any of the Laws of Nature is possible on Earth; anything which violates the Laws of Nature is not possible anywhere in the universe.
The fact is that all the scientific evidence strongly suggests that God does not, nor ever had any kind of intercourse with any human. For one thing, for God to communicate with humans as is described by the Words there would need to be some kind of "Magic", a violation of the unbreakable Laws of Nature. Any scientist will tell you that is impossible. Even the some of the Words say "And he (God) said, Thou canst not see my face: for there shall no man see me, and live". Exodus 33:20.
The result of this confusion on what is or is not God's will, is the chaos and immorality that pervades humanity. There is no ONE word on which we can base our morality, there is no absolute yard stick by which we can measure human activity, no marker separating good from evil! What is good in one society is evil in another.
On the other hand, children as the purpose of life has scientific proof in the fossil record, and having children as the purpose of life gives us the absolute by which we can measure good and evil. What is good for the children of Earth is right and good; what is harmful to the children of Earth is wrong and evil. Is it difficult to tell what is good for children and what is harmful to children? Absolutely not! If you have a happy child that matures into a moral productive adult then you got it right, if you have an unhappy child or one that matures into an immoral or non productive adult, you got it wrong.
We can also add that the welfare children are the most common desire and bond that connect one society to another, world wide!
Moreover there is no need to give up our faith in what ever God we believe in. I am sure that most will agree that we cannot go wrong if we give better care and priority to Earth's children. By making Earth's children the priority of society we for fill God's intention that humans propagate and multiply far better than humans ever have before because we will stop killing off the best our children have to offer. This is the only purpose God intended for which we any scientific evidence at all! We have a 3.2 billion years record of life doing just that, a record that is written in stone as the Ten Commandants were written in stone.
Consider this… If God exist and God intended a "purpose" for humanity, there must be some clue somewhere as to what that intended purpose is. If there is no clue, no way for humanity to understand God's will, then any purpose or meaning to human life is pointless. It's like a king telling his servant, "bring me what I want or I will punish you severely!" The poor hapless servant cannot comply with the king's wishes because he doesn't know what the king wants. Nor can he know unless the king gives him some kind of clue to what he wants. The fossil record is the clue to the purpose of life humanity has searched for since the beginning.
Many will say that God's will is spelled out in the Word of God (i.e. Koran, Bible, etc.) but which of the 2500 different God's that have been invented by humanity over the past 200,000 years is the correct one? Without some scientific provable evidence one Word is as good as the next. A person can chose one Word over another based on faith only, and that faith is the faith that your parents and society taught you to believe in as a child. Had you been born into a different culture with a different faith, you would probably practice the faith you were raised in as 5 or 6 billion other individual humans do. "We are what we are taught to be as children."
Herein lays both the reason for and the solution to all of humanities problems! The problem is that humanity does not teach its children to be all they can be, rather it puts great store in teaching children to conform to the present society's culture and norms. What humanity should be teaching its children is the "Truth" and "Reality" of human existence, and they should be taught this with the same zeal we now practice in the propagation of religion and culture.
How do we know what is the real truth and reality of human existence. That is simple! The universe came with an instruction manual which science and the scientific method has allowed us to decipher. We call this instruction manual the "Laws of Nature!" The Laws of Nature are constant, consistent and inviolable across time and space. They are the only absolute known to science. If the Laws of Nature were not constant, consistent and inviolable across time and space, none of the technology humanity now depends on would be possible. If something conforms to the Laws of Nature then it is true and real. If it violates any part of the Laws of Nature, it is false and fantasy. We have millions of scientist who are capable and who have the technology to prove or disprove any hypothesis concerning truth and reality. In order to insure we teach human children only truth and reality we must insure that everything we teach them conforms to the Laws of Nature as we understand them.
Perhaps the most insidious thing that has been taught to children over the past 200,000 years is the belief in "magic" and "miracles" through fairy tails and religious instructions. The fact is there is no such thing as magic or miracles because such things violate the constant, consistent and inviolable Laws of Nature!
Herein lays the primary reason humanity has failed to achieve peace and goodwill among all humans. Human children are born with a very acute and accurate "bullshit" detector. Children learn at a very young age that there is no magic or miracles in life and in the process learn that they have been lied to by their parents and society. Having learned that they have been lied to then gives the child permission to lie themselves, even to lie TO themselves about the reality they face. And this of course leads to the commission of immoral acts. The children reject the morality society tries to teach them simply because they believe it is another lie. This fact has been written about since the beginning of human history as evidenced by the story of Cain and Able. Children simply do not believe in ANY absolute morality because such has never been demonstrated to them. Could any human ever conceive of doing any immoral act if they knew for sure they would spend eternity in Hell for doing so?
If we do not lie to children about ANYTHING then children will trust their parents and society and follow the morality code accepted and taught by the society.