Admittedly, we do not know how it that anything (such as a physical universe) exists, let alone exactly how it came about that life came into existence. It is often suggested that there must be a God since it is impossible for anything to come into existence spontaneously through "self-creation" and equally impossible that anything existed forever in the past. Regardless of how elementary the very first particle of matter (or energy) and regardless how long ago it first emerged, it must have come from somewhere and through some process. In the minds of many people, the only logical explanation for the existence of the universe and (especially) of life is that it must have been created by a God. However, there are serious logical problems with that belief. First, it necessarily relies on completely circular reasoning: either spontaneous existence from nothing is possible or it is impossible; it cannot be impossible for the universe but require no explanation for the supposed spontaneous self-creation (or perpetual) existence of God. That fundamental logical problem cannot be resolved by defining God as "that which requires no creator" or as "that which has existed forever." Instead of answering the question of where we came from, the supposition that it is the work of a supreme creator only adds another layer of questions that cannot be answered any more easily than...

Conversely, there is absolutely no objective evidence of any kind to suggest that the existence of any God is more likely than God's non-existence. If one considers any of the moral attributes typically associated with cultural beliefs in God, that introduces are more contradictions than answers. Why would a benevolent God allow famine, disease, and misery? Why would a God allow unmitigated tragedies? Why would a benevolent and all-powerful God create a predatory natural food chain instead of a system that required horrific pain and trauma of prey or the slow starvation of predators?
Ultimately, there is less need to explain where (and how) the universe (and life) came to be than there is to explain where (and how) God came to be because there is direct evidence of the former and none for the latter. Explaining the existence of the universe by the supposed will of a God only pushes the question of existence another step further. Without any objective evidence to support the belief in a God, that belief must logically be rejected.