My discussion with @Kub933 got me going down a rabbit hole of civilizations that were atheistic. While there is no truly atheistic civilization free of spiritual beliefs, but the Pirahã people are close. They have a fascinating culture that is primarily interested in direct experience and facts, and seemingly uninterested in belief - although there are exceptions. Below is the wikipedia entry on their culture:
As far as the Pirahã have related to researchers, their culture is concerned solely with matters that fall within direct personal experience, and thus there is no history beyond living memory. Pirahã have a simple kinship system that includes baíxi (parent, grandparent, or elder), xahaigí (sibling, male or female), hoagí or hoísai (son), kai (daughter), and piihí (stepchild, favorite child, child with at least one deceased parent, and more).[6]: 86–87
Daniel Everett states that one of the strongest Pirahã values is no coercion; one does not tell other people what to do.[7] There appears to be no social hierarchy; the Pirahã have no formal leaders. Their social system is similar to that of many other hunter-gatherer bands in the world, although rare in the Amazon because of a history of horticulture before Western contact (see history of the Amazon).
Although the Pirahã use canoes every day for fishing and for crossing the river beside which they live, when their canoes wear out, they use pieces of bark as temporary canoes. Everett brought in a master builder who taught and supervised the Pirahã in making a canoe, so that they could make their own. However, when they needed another canoe, they said that “Pirahã do not make canoes” and told Everett he should buy them a canoe. The Pirahã rely on neighboring communities’ canoe work, and use those canoes for themselves.[7]
Pirahã build simple huts where they keep a few pots, pans, knives, and machetes. They make only scraping implements (for making arrowheads), loosely woven palm-leaf bags, bows, and arrows.[5] They take naps of 15 minutes to, at the most, two hours throughout the day and night, and rarely sleep through the night.[6]: xvii, 13, 70, 79
They do not store food in any quantity, but generally eat it when they get it.[5] Pirahã have ignored lessons in preserving meats by salting or smoking.[5] They cultivate manioc plants that grow from spit-out seeds and make only a few days’ worth of manioc flour at a time.[5] They trade Brazil nuts and sex for consumables or tools, e.g. machetes, gunpowder, powdered milk, sugar, whiskey. Chastity is not a cultural value.[7] They trade Brazil nuts, wood, and sorva (rubbery sap used in chewing gum) for soda-can pull-tabs, which are used for necklaces.[5] Men wear T-shirts and shorts that they get from traders; women sew their own plain cotton dresses.[5]
Their decoration is mostly necklaces, used primarily to ward off spirits.[6]: 74 The concept of drawing is alien to them and when asked to draw a person, animal, tree, or river, the result is simple lines.[8] However, on seeing a novelty such as an airplane, a child may make a model of it, which may be soon discarded.[9]
According to Everett, the Pirahã have no concept of a supreme spirit or god,[10] and they lost interest in Jesus when they discovered that Everett had never seen him. They require evidence based on personal experience for every claim made.[7] However, they do believe in spirits that can sometimes take on the shape of things in the environment. These spirits can be jaguars, trees, or other visible, tangible things including people.[6]: 112, 134–142 Everett reported one incident where the Pirahã said that “Xigagaí, one of the beings that lives above the clouds, was standing on a beach yelling at us, telling us that he would kill us if we go into the jungle.” Everett and his daughter could see nothing and yet the Pirahã insisted that Xigagaí was still on the beach.[6]: xvi–xvii
I’m watching this documentary on them at the moment:
