Remove Christianity and civilization would soon smell better.

[Confused Ape]

I'm no scientist, but in my not-so-professional opinion, it comes down to people fearing death, and not wanting to accept that life simply ends when we die.

It could be a bit more complicated than that. Neuroscience is discovering that the human brain could have a lot to do with religious belief. A good introduction to this is the BBC documentary God On The Brain

It seems that Shamanism is the world's oldest religion.

Shamanism (/ˈʃɑːmən/ shah-mən or /ˈʃeɪmən/ shay-mən) is a practice that involves a practitioner reaching altered states of consciousness in order to encounter and interact with the spirit world and channel these transcendental energies into this world.[2] A shaman is a person regarded as having access to, and influence in, the world of benevolent and malevolent spirits, who typically enters into a trance state during a ritual, and practices divination and healing.[3]

Shamanic practices may originate as early as the Paleolithic, predating all organized religions,[84][85] and certainly as early as the Neolithic period.[85] Early anthropologist studies theorise that shamanism developed as a magic practice to ensure a successful hunt or gathering of food. Evidence in caves and drawings on walls support indications that shamanism started during the Paleolithic era. One such picture featured a half-animal, with the face and legs of a man, with antlers and a tail of a stag.[86]

There's still the question of how they discovered altered states of consciousness, of course, but the human brain works in mysterious ways.

An entheogen ("generating the divine within")[59] is a psychoactive substance used in a religious, shamanic, or spiritual context.[60] Entheogens have been used in a ritualized context for thousands of years; their religious significance is well established in anthropological and modern evidences. Examples of traditional entheogens include: peyote, psilocybin mushrooms, uncured tobacco, cannabis, ayahuasca, Salvia divinorum, Tabernanthe iboga, Ipomoea tricolor, and Amanita muscaria.

Entheogen - Africa

The best-known entheogen-using culture of Africa is the Bwitists, who used a preparation of the root bark of Tabernanthe iboga.[32] Although the ancient Egyptians may have been using the sacred blue lily plant in some of their religious rituals or just symbolically, it has been suggested that Egyptian religion once revolved around the ritualistic ingestion of the far more psychoactive Psilocybe cubensis mushroom, and that the Egyptian White Crown, Triple Crown, and Atef Crown were evidently designed to represent pin-stages of this mushroom.[33] There is also evidence for the use of psilocybin mushrooms in Côte d'Ivoire.[34] Numerous other plants used in shamanic ritual in Africa, such as Silene capensis sacred to the Xhosa, are yet to be investigated by western science. A recent revitalization has occurred in the study of southern African psychoactives and entheogens (Mitchell and Hudson 2004; Sobiecki 2002, 2008, 2012).[35]

Psilocybe cubensis

Effects usually start after approximately 20–60 minutes (depending on method of ingestion and stomach contents) and may last from four to ten hours, depending on dosage. Visual distortions often occur, including walls that seem to breathe, a vivid enhancement of colors and the animation of organic shapes. At higher doses, experiences tend to be less social and more entheogenic, often intense and spiritual in nature.[citation needed]

Maybe religion started because our distant ancestors decided to try a new mushroom for lunch.