On very rare occassions, scientific writing can be clear and poetic at the same time. As I prepared my lecture about Charles Darwin's evolutionary hypotheses concerning religion for the European Society for Evolutionary Biology (ESEB) this year, I was amazed by the dense information and sheer beauty of the introduction Darwin gave to the religion subchapter in his "Descent of Man" (1871), page 65.
Let us take a look at those five introductory sentences framing Darwin's evolutionary perspective on "Belief in God - Religion".
"There is no evidence that man was aboriginally endowed with the ennobling belief in the existence of an Omnipotent God. On the contrary there is ample evidence, derived not from hasty travellers, but from men who have long resided with savages, that numerous races have existed and still exist, who have no idea of one or more gods, and who have no words in their languages to express such an idea.”
In his opening sentences, Darwin is refuting the idea of an "Urmonotheismus", a primordial monotheism. Instead, he asserts that some "savage" traditions have no concept of higher deities (such as mono-, poly- or henotheism), thereby bringing up his central argument: That contemporary beliefs and religions evolved from very simple beginnings, too.
“The question is of course wholly distinct from that higher one, whether there exists a Creator and Ruler of the universe; and this has been answered in the af-firmative by the highest intellects that have ever lived.”
Proving his sound education in anglican theology (the only university degree Darwin mastered throughout his life), Darwin then explains that evolutionary (that is: empirical) studies of religiosity and religions neither proves nor disproves the existence of (a) God. Instead, these questions are to be discussed in the metaphysical realms of philosophies and theologies. Darwin is adding a curteous nod to (evolutionary) theists, many of whom - i.e. Alfred Russel Wallace - accompanied and supported his scientific mission.
“If, however, we include under the term "religion" the belief in unseen or spiritual agencies, the case is wholly different; for this belief seems to be almost universal with the less civilised races. Nor is it difficult to comprehend how it arose.”
If theistic religions evolved from earlier forms, we would need a broad and workable definition. Darwin is offering "the belief in unseen or spiritual agencies" - in contemporary words: supernatural agents (or, even more precisely: superempirical agents). Ancestors, spirits, angels are encompassed by this definition as are sentient mountains and trees, Buddhist bodhisatvas, Jain tirthankaras, Shintoist khami or even Raelian space aliens and, of course, any poly-, heno- or monotheistic deities.
It is an interesting coincidence that, although only a small number of contemporary colleagues are aware of Darwin's own works on the matter, contemporary definitions of supernatural (superempirical) agents became the most successful and prevalent working definitions in interdisciplinary studies of religion.
For that, I am assuming a single reason: Charles Darwin had been right on this topic.