oniongrass:

“What if ghouls were originally just cannibalistic humans?” That’s…not how evolution works. In the slightest. At all.

Hmm… Maybe ghouls were humans that had a mutation that made them cannibals, as well as adding certain traits?
Or, maybe the Kagune is a parasite that latched on to certain people and pushed them thru the transformation, like with Kaneki, and when half-ghouls breed their descendants eventually become the full ghouls we see today?