It seems that Mario and Luigi haven't aged at all throughout the games, but the Kongs have. Therefore, they must live in different dimensions of the gaming world with different rules governing space-time. Who's to say Mario isn't 1,000 years old? Also consider that Yoshi doesn't seem to have aged at all from SMW2:YI to SMW, while Mario and Luigi have certainly aged quite a bit. So, when Mario, Yoshi, and Donkey Kong meet (in the original Donkey Kong, SSB, SSBM), they must cross dimensions out of their home worlds. This is all theoretical, of course, since they're all video game characters living in the world of Nintendo. :)
Bozone, n.:
The layer of gas surrounding a person which prevents good ideas from penetrating.