There's the fuzzy thought that our current cycle of history might have happened before. Here's the rational logic. The human body digests food. Food is made up of living matter. Living matter is chemical computer code.
Computer code relies on subroutines.
Our bodies may depend on subroutines we don't know about yet but which get Genetically Modifed - changed. We'll know about the subroutine when the body fails. Genetic modification of these subroutines is dangerous in two ways. They are pieces of software which are used as hardware building blocks. The hardware is the product of an infinite evolution of software.