In the year 2205, they discovered that people who were left-handed put out dangerous radiation, which was called "Left-Handed Radiation," after the man who discovered it, Dr. Left-Handed.
People were not exactly sure what this radiation did to people - some wore helmets in case it made you go bald, others wore ski masks in case it made you do rash violent crime. Others used it as an excuse to wear full body casts, which was something many people had been waiting for a decent excuse to allow them to do it.
Things got dangerous when people began wearing lead coffins to prevent themselves from being exposed. The working day went from 8 hours to 6 hours to 3 hours, and finally went to -13.5 hours, from a combination of poor diet, lack of sleep, and other things the government didn't want you to know about.
This worried Dr. Left-Handed, for he thought it was all caused by his radiation. So he said to the massed thousands outside his bedroom, "Oh sorry. It was really the dog."
Foolishly, they believed him and went back to walking around completely naked in the presence of left-handed people. Of course, Dr. Left-Handed was just saying that, and in fact was quite wrong about the emissions of these evil left-handed radiationists, and thus humanity was doomed.
In the crumbling aftermath, new life spawned, but it looked around and went "Nah."