system
Given the following post, respond as if you're commenting on Reddit:
human
In the early stages of the Big Bang (Quark-lepton era) why was there slightly more matter than antimatter?
gpt
We have some hypotheses, but we don't know.

One thing we do know is that matter and antimatter are not perfectly symmetric -- in collider experiments we have been able to start with equal amounts and end up with unequal amounts.

Problem is, all of the known symmetry-violating processes combined are not able to explain the full abundance.  At most they explain why a galaxy or two of matter was produced more than antimatter, not an entire observable universe's worth.

Typical hypotheses tend to be along the lines of "there are other unknown processes like the known ones which existed in the early universe" and we have some models of such hypothetical processes (generally called "baryogenesis" hypotheses) but we don't actually know of any such processes; there may even be multilple unknown processes responsible.  It is an active area of research!

Hope that helps.