forgive the obvious pun on darwin, but i find it is quite accurate to describe the work i will herein present.
it has been established, debated, argued for and against, thoroughly tested and finally highly accepted by all biologists and most others that the origin of the species can be explained by natural selection of various varieties with heritable traits which vary across members of a species and affect the ability of the organism to reproduce.
these three things are the basic requirements for natural selection to act upon a body causing evolution over periods of time.
i propose that these basic requirements are met by religions of today and those of times past, and thus the origin of such religions is explained similarly to that of the species.
in a species, for example humanity there are variations such as height, proportional brain size, and skin tone which affect our ability to survive to the age of reproduction, and then to produce offspring which survive to the age of reproduction. height and ability to stand upright affected our ability to see predators over tall grass and survive, brain size affected our tool making abilities which affected all areas of man's life, and skin tone affects the propability of developing melanoma of the skin. all of these traits would be passed down because those with them are more able to reproduce than those without them.
but where can these different traits be found in religions? One can observe the evolution of christianity out of judaism to find examples of such variation. thanks to historical texts and mythological texts we have well preserved information that the first christians were jews and considered themselves to still be jewish after jesus was born. however the initial variation in between them was that one variety of judaism thought jesus was the son of god, while the others thought he was either insane or a heretic. the teachings of jesus changed many parts of this variety almost simultaneously(a rare occurance, but a useful example for it shows in extreme how these variations affect success). the teachings of jesus provided one extreme change which i will discuss: the change from action based entry to heaven to acceptance based entry. in the action based entry to heaven that the original variety believed in one was made to practice a difficult way of life which was not appealing to converts(to be explained later). the faith based new variety was far more appealing, if one believed in jesus as their savior one thought they would go to heaven, far more appealing to converts(discussed next).
heritability of physical traits in organisms is now much better understood in the past. thanks to the gene theory we have developed an understanding of how chromosomes pass on information with variation to new generations(produced via reproduction). this heritability is one of the important factors in natural selection, if a variation isn't heritable it isn't involved in natural selection.
what though, could be the method of heritability in religion? beliefs do not reproduce physically, they have no physical form. in order for a belief to be inherited into a new generation it must be taught. there are two major methods of heritability of beliefs through generations, namely indoctrination and conversion. this is vastly different from heritability via reproduction and the passing down of genes in that there are two methods in the heritability of beliefs. a religion can be strong in one yet weak in another and still survive. one more question which must be adressed in the heritability of religions is "what are the heritable units?". as we see in species, reproduction is not a conscious action of the whole species, each individual reproduces with variability on their own to make the whole subject to natural selection. this is also the case with religion, individual beliefs are equivelant to genes in that they are passed down from one generation to another through indoctrination and conversion. but not only one individual, or not merely two individuals is involved in the reproduction of beliefs. throughout the lifetime of an organism which carries beliefs(as an organism carries genes) it is affected by indoctrination by its parents from a young age, and subject to attempts at conversion throughout its lifetime. in this way the heritable units(beliefs) of multiple types of religions can be represented in one individual and passed down by that individual.
as we have seen, both organisms and religions are subject to variability of heritable units. i have explained briefly how the effects of certain heritable traits effect the success of an organism, and for further information one can easily find their own research on it, for brevity i shall not delve further into it here.
however, on the subject of affects of beliefs on a religion's ability to be represented in the next generation i feel that merely the example of faith versus action in judaism and christianity is not sufficient for such bold a claim as my own. another example of exactly how a trait affects a religion's ability and method of reproduction (for one must always keep in mind that there are two such methods, both of equal or nearly equal importance.) is the difference between fundamentalist creationists and christian religions more closely related to religions/belief structures that base their beliefs on observation. the beliefs of fundamentalist religions are specialized for indoctrination, and have very weak powers of conversion. fundamentalist creationist communities are closed societies. they do not welcome new members(a result of their beliefs and reaction to any form of disagreement) and their belief structure provides significant discouragement from any attempt to leave. often the penalty for trying to leave is death or religious condemnation. through indoctrination that such religious condemnation causes one's soul to be unacceptable to their god the religion is able to keep up a large percentage of the indoctrinated membership while not making any new converts. we then look at a christian religion on the opposite end of the spectrum(i will use the UMC as an example), apostasy is discouraged by religious means but there is no physical backlash against the abandoner by the community. this means that the religion's ability to practice solely indoctrination is diminished as indoctrinated members are subject to conversion to other beliefs. thus the religion in order to survive must have some type of trait which allows it to convert enough members to make up for the loss. this comes in the form of the less extreme views which because they do not differ greatly from other societal norms encourages some members of other beliefs to change, believing their souls will be saved for little cost.
as with all theories, this is a work in progress. i am no theologian so i cannot provide every belief of any religion without much research, just as darwin could not study each and every trait of each and every species. however as with his theory, the evidence i've provided for my own is sufficient unless evidence can be brought against it. so i say, bring on the gauntlet all!
*edit, fixed a spelling error in the first sentence.