My homebrew setting is so far beyond separating cultures from genetics: the different races are wholly alien to each other to the point where the idea of them sharing a common culture is silly. Examples:
  • Dwarves' "beer" is a symbiotic yeast that forms a critical role in their reproductive cycle. They're an all-male species whose young grow in fungal cysts beneath their holdfasts. Their beer brewing and stone working is instinctive and necessary. There can't be a tribe of dwarves that doesn't brew beer because they wouldn't last a single generation. There couldn't be a tribe of dwarves that doesn't dig their civilizations into mountains because the necessary conditions for the cysts to form wouldn't exist in another environment.
  • Goblinoids are a single eusocial species, with each of the goblinoid "races" actually being a distinct caste ("caste" in the biological sense, as in workers, soldiers, drones) within the warren. They are intelligent and free-willed, but the pheromones that direct their behavior are powerful motivators that would make significant deviation from the duties of the caste extremely unusual. For example, goblins derive almost sexual pleasure from theft because they're "worker bees" gathering resources for their warren. A goblin can learn not to steal, but they will always want to.
  • Orcs were created by interbreeding humans and goblinoids (by the naturally amoral elves, see below) and a skull/pelvis mismatch prevents natural childbirth, necessitating surgical removal of infants from the womb. Because of the goblinoid DNA, a "litter" of 6-12 infants forms in the womb, but the orc fetuses will begin to strangle each other during the second trimester, a battle which continues all the way up to birth, so when the mother cuts herself open when her labor pains begin, she finds a single infant (or rarely twins, hands still at each others' throats) and the remains of its siblings. This is not a biology that will tolerate weakness, culture be damned. If you don't have a str and con bonus, you don't even make it out of the womb alive.
  • Elves are the most closely related to humans, but they evolved as solitary apex predators rather than cooperative social animals. As such they have none of the social instincts humans enjoy like guilt and empathy: they are an entire species of sociopaths. "Good" elves exist, but goodness is a learned/taught behavior developed for practical purposes. They can decide to be good, but their instincts do not give them the tools which would make it easy.

They all have culture, but their culture is informed by their biology. Some tribes of dwarves pray for sons when their hormones cause them to wait for one, and believe that when their son arrives days later, crawling up from the depths, their prayer has been answered. That's culture, but a culture that wouldn't exist without their biology. Dwarves have no notion of gender at all: why would they? Goblinoids, by contrast, have four "genders" which are rigid and rooted in deep and very real biological differences. Orcs have no instincts which compel them to cut their wombs open as labor begins: this must be taught, and so it is an element of their culture. But it's a wholly necessary element of their culture, for birth wouldn't be possible without it. The manner in which this surgery occurs may vary greatly from tribe to tribe: in many the mother cuts the infant from her abdomen herself as a rite of passage. In others perhaps the father makes the incision, or a midwife, or someone else. But the cutting must occur. But no tribe could survive without some form of this ritual.