Dragon Ball Online/YMMV


 * Unfortunate Implications: The good news is that 216 years after the manga has ended, any human warrior can become a Super Saiyajin through his Saiyajin blood. The bad news? Considering there are ONLY TWO MALE SAIYAJINS IN EXISTENCE on last count, the only way possible for the Saiyajin bloodline to be this widespread is for Chichi and Bulma to be abandoned while their husbands go on a sexual rampage of such epic proportions that it would make the cast of Aki Sora and a 1960's Summer-Of-Love hippy blush.
 * OR... considering one becomes a Super Saiyajin by making a wish on the Dragon Balls maybe they didn't.
 * Shen Long can revive people from the dead, often in large groups, he can grant world domination, he can grant eternal youth, he can grant immortality (yes, that's different than eternal youth because it's also unkillable) and all sorts of other things. Magically giving someone a genetic ability isn't that far out there, especially with all the Dragon Clan Nameks on earth who could have made him more powerful, like Dende did.
 * OR Saiyans and humans are actually closely related, having had a common ancestor, and some of the genes required for the super saiyan transformation are already present in all of the Saiyan's human cousins, but not others, and Shenron inserts the genes that complete the ability to transform, or the remaining gene or genes have experienced sufficient genetic drift.