What is fundamental to all life that we have ever encountered? The answer, is DNA. Unless you count RNA viruses as alive, every single bit of life on this planet encodes the genes for its offspring using DNA. While DNA may be the tool life uses to reproduce, this is actually a bit of a self-centered way of looking at things. We don't so much use DNA as DNA uses us.
We are taught that the basic unit of life is the cell. And a cell is simply a self replicating structure built around a particular collection of DNA. Granted the DNA couldn't self replicate without all the supportive proteins, but those very proteins would not have their particular arrangement without DNA. But this wasn't a problem for some of the earliest strands of replicating nucleic acids. The conditions they formed in gave them just enough material to, by pure chance, construct a way to replicate themselves.
As mutations accumulated in the various offspring of this first replicating DNA strand, different populations began to compete over resources. Those early units of DNA that could make the most efficient use of resources, as well as gather it the fastest, were able to replicate the most readily. As time went on, the accumulation of mutations would guide different populations down different roads.
Some would eventually construct full cells around them so that they could move out of the chemical cradle that formed them. Some would have only the most basic of covering and would hijack the support structure of the self-replicating ones. Novel forms that made the best use of the environment would soon thrive where as those that stagnated would be out competed at faster and faster rates.
More complex cellular structures became required if the DNA that operated the cell hoped to be able to continue to replicate. Competition became fierce and the changing forms constantly found more exotic forms to be able to survive. These new forms were expensive to form and maintain, but as other niches filled up, they became the only way a lineage of DNA could hope to compete with other lines.
Some lines that diverged eons ago would begin to work together for the common goal of self-replication. The first Eukaryotes arose and, with their larger and more complex cells, found their own niche to exploit. Some of these newer models for DNA replication began to work together for the common goal. For if even one of them would replicate, then the shared DNA lineage would continue. Such communal behavior allowed for the first multicellular life. DNA no longer would just encode for a single replicating unit, but for the eventual diversification of its own progeny into more efficient ways for the DNA itself to replicate.
Eventually such multicelled life would take on even more elaborate formations to compete with other lineages of the first DNA. Such larger forms allowed for new resources to be exploited, including the dismantling of other DNA and their cells to maintain their own functionality. While such tactics was not new, the size of multicellular life allowed for an arms race of size to develop.
As size increases, more regulatory systems were required, especially with other complex DNA structures to contend with. One of these regulatory systems is the first nervous system. It allows for quick communication between cells so that the whole can find resources faster, escape predation more efficiently, as well as reproduce more readily.
The DNA strands that had the more efficient variations in this nervous system would become more successful under different conditions. It became so successful that the nervous system had to centralize if it had any hopes to quickly responding to the new stimuli its nervous system allowed it to detect. This line of DNA, began finding itself quite successful in a myriad of environments. All thanks to the DNAs extended support structure that we know as the central nervous system. Lines of DNA with this trait would compete amongst themselves just as their ancestors did and, eventually, the nervous system became able to make predictions about its environment. Intelligence is born.
Intelligence allowed for an understanding of the outside world. It allowed the DNA to respond to even more complex stimuli then it ever had before. One line of DNA eventually amassed the requisite genes so that the nervous system became advanced enough so that it could ask, "What am I?"
Being an imperfect system, this newly formed self-aware intellect could only make wild guesses as to what it was and where it came. Myths began to form to answer these questions. These myths would compete amongst one another, extensions of the DNA that spawned the minds themselves, if indirectly. Some would allow for greater survival, some less so and thus, were selected for.
The idea of experimentation arose and the DNA that exploited such refined ways of understanding the world thrived enough so that this tool of science was passed on. Eventually, after millenia, this intelligence had uncovered enough about itself and its world through its questions and resulting experiments that it could begin to accurately describe its own origins.
This line of DNA had, for the first time, understood what it was that life had been doing blindly for billions of years. Here, the supportive structure the DNA used to propagate had actually described its very existence. Natural selection, after going through a seemingly endless menagerie of new DNA defense and replication systems, developed a form that could see itself for what it really was.
There was no soul, no creation event, no supernatural guidance. Just strands of interconnected nucleic acids doing its best to out compete itself.