> But I'm not sure how they explain the refresh during birth/zygote formation. Probably it's just survivorship bias. When a organism has trillions of cells, it

> But I'm not sure how they explain the refresh during birth/zygote formation. Probably it's just survivorship bias. When a organism has trillions of cells, it can afford to have some fraction of them damaged. It just carries on with degraded function. When it has a single cell, all essential genes must be functional, or it dies before anyone knows there was a pregnancy. It's a bottleneck. The zygotes that made it to birth are the ones lucky enough to receive a minimally viable set of undamaged genes from both parents. Most couples try a lot before one successfull pregnancy.