Molecular biologist Dean Hamer has found a gene which he believes is associated with the self-transcendence aspect of spirituality. while he said that this gene does not specifically code for religion id does come for spirituality which influences our susceptibility to religious influence.
I am an agnostic, but...
I believe that religion is a manifestation of the needs and ideals of society, as well as other environmental impacts. In a sense god does exist. He/She has become a concept, common to many people and religions. He/She is a source of hope, meaning and ethical guidance which many people find they need to help them mentally and emotionally navigate their way through the increasingly chaotic and complex nature of society.
the argument about the existence of god, "Does god exist?", is doomed form the start. The question we should be asking is "Do you believe in god," as god is a immaterial concept rather that a material presence. Many religions teach that god is a incomprehensible concept, while they Believe in gods presence they also believe that a complete and definite knowledge of god is not possible by humans. (e.g. Allah has 100 hundred names but humans will only ever know 99)
Like with science, a completely definite answer can never truly be achieved, as all our knowledge is based on theories which best fit our observations. These theories develop and change over time, with new observations and experiences, becoming increasingly complex.
The answer as to wether or not god exists is based on our beliefs, you can argue for ever about whether or not god exists, but there will always be people who believe in god, people who don't believe and people who don't really care.