If that's true, your dad is a very rare case. In basketball, the decline starts earlier than in most sports. It's downhill for sure past the early 30's. The average age of an NBA player is 26. There are teams without a player over 30.
MMA is such a different deal than the other major sports, with people entering it at a later age, the impact of different styles on wear and tear, and the relative speed of competitors at different weight classes. Outside of the two heaviest weight classes, which are their own little world, 32-35 and it's going downhill.