Earth was decimated by "the big electron" around 250 years after the USS Outerra left to establish a new homeworld.
Or everyone got Carlin Syndrome and went mad.
Either one works for me.
Carlin Syndrome works for me, and is a cool Easter Egg
. Could be a "quest" reward in Anteworld. After investigating the ruin of a medical center, you're rewarded with a surviving record that gives a few details on the "syndrome," which was first contracted by someone named "John Doe Carlin."
Patient zero!