This can be good and bad too. Hence, I have an aversion for that word - "culture".
The genesis of almost all savagery, ruthlessness, and immorality against animals is from so called culture,
This is an insightful piece on the same topic:
A mental model is a simulation of "how things might unfold", and we all build and rebuild hundreds of mental models every day. A framing, on the other hand, is "what things exist in the first place", and it is much more stable and subtle. Every mental model is based on some framing, but we tend to be oblivious to which framing we're using most of the time (I've explained all this better in A Framing and Model About Framings and Models).
Framings are the basis of how we think and what we are even able to perceive, and they're the most consequential thing that spreads through a population in what we call "culture".
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Each culture is made of shared framings—ontologies of things that are taken to exist and play a role in mental models—that arose in those same arbitrary but self-reinforcing ways. Anthropologist Joseph Henrich, in The Secret of Our Success, brings up several studies demonstrating the cultural differences in framings.
He mentions studies that estimated the average IQ of Americans in the early 1800's to have been around 70—not because they were dumber, but because their culture at the time was much poorer in sophisticated concepts. Their framings had fewer and less-defined moving parts, which translated into poorer mental models. Other studies found that children in Western countries are brought up with very general and abstract categories for animals, like "fish" and "bird", while children in small-scale societies tend to think in terms of more specific categories, such as "robin" and "jaguar", leading to different ways to understand and interface with the world.
But framings affect more than understanding. They influence how we take in the information from the world around us. Explaining this paper, Henrich writes:
People from different societies vary in their ability to accurately perceive objects and individuals both in and out of context. Unlike most other populations, educated Westerners have an inclination for, and are good at, focusing on and isolating objects or individuals and abstracting properties for these while ignoring background activity or context. Alternatively, expressing this in reverse: Westerners tend not to see objects or individuals in context, attend to relationships and their effects, or automatically consider context. Most other peoples are good at this.
How many connections and interrelations you consider when thinking is in the realm of framings. If your mental ontology treats most things as largely independent and self-sufficient, your mental models will tend to be, for better or worse, more reductionist and less holistic.
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The basic force behind all culture formation is imitation. This ability is innate in all humans, regardless of culture: we are extraordinarily good imitators. Indeed, we are overimitators, sometimes with unfortunate consequences.
Overimitation ... may be distinctively human. For example, although chimpanzees imitate the way conspecifics instrumentally manipulate their environment to achieve a goal, they will copy the behavior only selectively, skipping steps which they recognize as unnecessary [unlike humans, who tend to keep even the unnecessary steps]. ... Once chimpanzees and orangutans have figured out how to solve a problem, they are conservative, sticking to whatever solution they learn first. Humans, in contrast, will often switch to a new solution that is demonstrated by peers, sometimes even switching to less effective strategies under peer influence.
— The Psychology of Normative Cognition, Stanford Encyclopedia of Philosophy, emphasis theirs.
We have a built-in need to do what the people around us do, even when we know of better or less wasteful ways. This means that we can't even explain culture as something that, while starting from chance events, naturally progresses towards better and better behaviors. That's what science is for.
Once the synchronized behaviors are in our systems, when we are habituated to certain shared ways of doing things, these behaviors feed back into our most basic mindsets, which guide our future behaviors, which further affect each other's mindset, and so on, congealing into the shared framings we call culture, i.e.: whatever happens to give the least friction in whatever happens to be the current shared behavioral landscape.
This is why, often, formal rules and laws do indeed take root in a culture: not because they're rules, but because the way they are enforced creates enough friction—or following them creates enough mutual benefits—that, like in the corridor lanes, crowds will settle into following them. This is also why, perhaps even more often, groups will settle into the easy "unruly" patterns.