Where did life and humanity originate? Humanity and life are one and the same, and we originated from the synthesis of organic unicellular organisms in a primordial Earth.
Why is there suffering, sickness, and death? Suffering is a broad term. Physical pain is a very rare evolutionary adaptation to make us more able to respond to our environment. Suffering can also be attributed to the materialist struggle that most engage in. Death exists because proteins break down and inhibit life functions.
What is the cure for man's suffering, esp. his existential lonliness? Once again, we come to the ambiguity behind the term 'suffering'. I see suffering as the consequence of the pursuit of materials and status, so the 'cure' is the cessation of these pursuits. As for existential lonliness, friends and other loved ones to share your life's experiences with seem to do the trick for most.
How does an atheist assign meaning to human activity? Is all meaning subjective, or do some activities have self-evident and objective worth and meaning. If so, what are these activities, and how to you arrive at their value? I can only speak for myself. I assign the same meaning to human activity as I do to all terrestrial activity. It is smaller than the tiniest grain of sand in the Sahara, in a universal sense, but on the personal level we must assign meaning to these activities to lead fulfulling lives. There is no objective way to assign values, neither 'good' nor 'bad' to any activity.
Are humans of more intrinsic value than animals? Why or why not? Humans are like all animals: Programmed neurologically to feel empathy for our own as a survival mechanism. There is no "intrinsic value" here, only our inherent preference for our own kind along with a society that seems to value other animals less.
How does an atheist determine what is moral or immoral, right or wrong. Is there any objective standard or principles? An atheist determines what is moral or immoral the same way any rational person might. I would do so by weighing an action's impacts, positive and negative. I would take into consideration my self-interests and balance them against whatever negative repercussions my actions might have on others.
What type of government does atheistic philosophy translate into? How does it understand the relationship between man and government? What type of government structures flow from an atheistic world view? Does it merely rely on someone else's system of thought, like the assumptions of naturalistic science? Political views differ among atheists as they do among almost any group. Ideally atheists would likely prefer a humanist government, but realistically speaking, American atheists are pigeonholed into choosing the lesser of two evils.
How does atheism view religions and religious faith? What about metaphysics? Is atheism purely materialistic and naturalistic? Each atheist has their own views on these things. I personally see religion as a cultural relic that has more destructive potential now than ever before, and a factor inhibiting greating understanding throughout the world.
Who are the authoritative writers/books of atheism? What are the central tenets of atheism, and if they have a "greatest commandment," what is it? For example, arguably, Christianity's is "Love the Lord your God with all of your heart, mind, soul and strength, and love your neighbor as yourself." Atheism has no tenets or commandments. There are no 'authoritative writers/books' of atheism, only authors who happen to be atheists. Atheism is one facet of a worldview, not a worldview unto itself. Some eminent atheist authors are Sir Richard Dawkins, Stephen J. Gould, and Douglas Adams, though their beliefs by no means represent the views of all atheists. As for one "greatest commandment", I would say that personally, my guiding principle would be the Golden Rule: Do unto others as you would have them do unto you. I think this is the basis for every other system of morality established in the world.
What happens after we die? The same thing that 'happened' before we were born. Why should there be any difference? If your conciousness can be brought into the world through your parents' union, it can just as easily return to the same state it occupied before that-- not existing.