system
Given the following post, respond as if you're commenting on Reddit:
human
Is there some fundamental reason why there are three generations of quarks and leptons, instead of (say) 2 or 4 or 13 or an unlimited number?
gpt
We don't know. Within the Standard Model of Particle Physics, there is no fundamental reason. Some Grand Unified Theories require there to be exactly three generations of fermions, so there may actually be a fundamental reason, but we haven't confirmed it yet.