However, grand parent raises a good point about reduced diversity, which is bad at the species level. There is really no way to guard against this because:
1. Even though diversity is good at the species level to safeguard against future disaster, everyone will race to have the same set of (currently) desirable traits. Framed another way, since human genetic diversity is a public goods, few people will help maintain it at the cost of their own benefit
2. While we could theoretically understand the genome in full, I'd argue it's impossible to foresee all the potential disasters that can wipe out a genetically homogeneous humankind.