Earth dating wiki
The underlings attacked the dojo and in the aftermath both the monsters and all but two of the students end up dead.
Satan's ability to convince them that his opponents cheated somehow.
Earth itself is wished back into existence a number of times through this method. With the exception of the uncommon hair colors and occasionally odd features (ranging from longer lifespans to werewolfism, to Tien Shinhan's third eye).
Dragon Ball humans are identical to their real-life counterparts.
Dinosaurs and other extinct creatures in the real world still roam the Dragon World freely, while the characters fly around in futuristic levitating cars and houses that can be shrunk down to convenient travel-sizes.
The first major unnatural tragedy known took place some 300 years prior to the beginning of the series.