For the universe to exist as it does now, there must have been an imbalance between matter and antimatter early on, which may have been caused by neutrinos
Source:
https://www.newscientist.com/article/2240543-neutrinos-may-explain-why-we-dont-live-in-an-antimatter-universe/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home