Random thought after reading all the philosophical and semantics tangents in the comments here: A good example of a memetic equivalent of endosymbiosis could b

Random thought after reading all the philosophical and semantics tangents in the comments here: A good example of a memetic equivalent of endosymbiosis could be Christianity - Catholicism in particular. Historically, as Christianity spread around the world over the two millenia, it would often adapt and absorb indigenous beliefs and practices of converted populations[0]. Many would die out over time, but some got integrated into the core and exported globally. It's just the right time of year to think about Christmas[1]. Can you imagine Christianity without one of its two core holidays? That makes it probably the closest memetic equivalent of a mitochondria - you can still see in it the distinct outline of an ancient Roman festival that was absorbed early on, but all of its memes live on in Christianity. In our times, the holiday is vital to the overall faith, and itself could not exist independently[2]. -- [0] - I've always been taught that this was intentional slack to make it easier for people to accept a new religion, but nowadays I feel it might have been a fundamentally unavoidable outcome. Maintaining organizational coherence and belief consistency at a scale of a whole continent requires communication and bureaucratic technologies that didn't exist until the last 100-200 years. [1] - Or at least so most shops would have me believe; in western commercial calendar, Christmas starts when Halloween ends. [2] - Well okay, I admit this might be a weak part of the analogy - in the western world, Christmas got commercialized to the point it could likely survive as an independent secular tradition.