In the Journal Cell , May 27th 2021, is a paper titled Parental genome Unification is Highly Error-Prone in Mammalian Embryos. What is described is the complex union of the male and female genomes following fertilization. The complexity of this process leads to chromosome errors and formation of micronuclei which changes are incompatible with healthy embryo development. My question is: why has evolution maintained a high error rate in such an important process (parental genome unification)? Why has natural selection not improved the fidelity of this process?