system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] Why are Humans one of, if not the, only species with many diverse cultures?

The vast majority of species shown have a single unifying culture or belief. Fluctuations are mostly on an individual scale. Whenever beliefs or cultures are discussed, it is said that "Species X believes this, Species Y considers this rude, Human culture X believes this". Especially when discussing the afterlife, people tend to bring up 3 human belief systems, as well as 2 alien ones, each representing an entire species.
gpt
Humans were quick to develop warp drive. Most species take a lot longer, so there's a lengthy period in their history where they've got extremely good telecommunications technology while still being confined to just one solar system. This has a homogenizing effect on culture. Humans developed warp drive unexpectedly (they'd just come out of a massive global war, they were quite fragmented and backward at the time) which allowed them to radiate out to remote star systems before they'd been able to homogenize quite so much.