From evolutionary perspective, merely "doing things for generations" has no direct impact on genes. (Otherwise, Jewish boys would be born without the foreskin.)

From evolutionary perspective, merely "doing things for generations" has no direct impact on genes. (Otherwise, Jewish boys would be born without the foreskin.) However, it can have an indirect impact, if doing things is also associated with rewarding the people who do the things, and/or punishing the people who don't. For example, people living in a civilization have "domesticated" themselves by killing the criminals, i.e. the people who were least capable/willing to follow the rules of the society. So the answer depends on whether our hypothetical stoic ancestors in the alternative universe also rewarded each other for being stoic, and or punished those who failed to be sufficiently stoic. Because there would always be a few exceptions to the rule, for example people with new mutations. If the stoic ancestors consistently rewarded the people who demonstrated stoic virtues, for example by considering the virtues necessary for holding an important office or inheriting family property -- so that their more stoic kids would on average have better jobs, higher status, more money, and more kids that survived to adulthood (regardless of how much they would proclaim that things such as jobs, status, money, and kids don't really matter), and their less stoic kids on average ended up poor and childless -- then today, most of us would be genetically selected to be highly stoical. (Or perhaps, highly stoical until we safely get to the positions of power, and then corrupted by it.) However, being more stoic wouldn't necessarily make us reasonable -- perhaps the stoic civilization would develop their own unreasonable behaviors. For example, I could imagine a stoic society that opposed science and progress because "meh, we don't need all that fancy new stuff; the true philosophers are content with whatever they have". Or they wouldn't develop medicine and cure diseases because "the only important thing is whether in your mind you are free"; etc. On the other hand, if the stoic ancestors were like "eh, I don't care if that guy wants to be a king; I am okay with being a slave as long as my mind is free", then the stoics would be quickly outcompeted by... whoever showed up for the race.