13. Why does life require rejuvenation across generations?

If offspring inherit some of the parental deleteriome (via germline, which becomes older as parents age), biological age will increase across generations, quickly compromising species viability. While the germline is well protected, it is difficult to entirely avoid its deleteriome increase. Therefore, successful reproduction requires germline or early embryonic resetting that restores a low-deleteriome state. The existence of this reset is central to the ground zero concept: life repeatedly finds a way to return to a youthful baseline, even if somatic tissues cannot fully do so. Some biological age reduction may also occur via germline selection and germline reset. Understanding what is reset, and what is not, provides a blueprint for engineered rejuvenation.