Are there cultures without a Golden Rule?

Yes, but the picture is more interesting than "yes or no."

Within the in-group, almost every codified culture has some form of mutual obligation. The genuine variation is at the boundary of the in-group: which beings count as "us," and which fall outside the protection the principle confers. Warrior codes (Spartan, Mongol, Viking, samurai) codified intense reciprocity within the warrior class while explicitly excluding outsiders from the same protections. Slave-holding societies, including those of Confucius, Marcus Aurelius, and the Eloquent Peasant scribe quoted in the parent essay, practiced reciprocity among free citizens while excluding the enslaved within the same society. Caste systems specified duties by station rather than reciprocal obligation between equals. Aristotelian virtue ethics, despite living next door to Stoicism, centered on arete (excellence) rather than reciprocity, producing a related but distinct ethical structure.

The Golden Rule's history isn't "did this culture have it?" It's the slow expansion of who counts as "us." Peter Singer makes this argument in The Expanding Circle (Princeton University Press, 1981): the historical work of moral progress has been extending the circle of reciprocal obligation outward, from tribe to city to nation to humanity to (now contested) other sentient beings.

The data is asymmetric. Long-lasting societies have been overwhelmingly communitarian and reciprocity-centered: Chinese dynasties, Japanese imperial and feudal periods, Indigenous nations on multiple continents, monastic Christianity, Islamic caliphates, the Bantu Ubuntu-cultured kingdoms of southern Africa. Most of these systems endured for centuries to millennia.

Cultures with weaker reciprocity ethics at scale tended to be either short-lasting (expansionist empires that collapsed within a few centuries) or in-group-only (warrior confederations whose survival depended on continuous external threat). The anthropologist Christopher Boehm makes the broader case in Moral Origins (Basic Books, 2012): cooperative ethics are load-bearing for any society that lasts more than a few generations, because the alternative is internal collapse.

The honest framing isn't "every culture has the Golden Rule." It's: every culture that has lasted long enough to leave a codified ethical tradition has codified some form of mutual obligation, but where it drew the boundary of "us" varies enormously.