It has been explained by a lot of reviewers here so I don't feel the need to add more to it. Daughter is now becoming Mother to a whole new, psychologically and emotionally, superior generation of humans, and it seems Mothers' plan has worked. Just one big BUT:
We can see that Mother clearly has no problem with disposing of/aborting/killing any imperfect child it has raised. But she raised Daughter to value human life so it's fair to assume Daughter herself will not be killing any of the children she is raising, even the imperfect ones. So with imperfect humans raising more imperfect humans won't humanity eventually end up in the same place it was before the extinction?..
We can see that Mother clearly has no problem with disposing of/aborting/killing any imperfect child it has raised. But she raised Daughter to value human life so it's fair to assume Daughter herself will not be killing any of the children she is raising, even the imperfect ones. So with imperfect humans raising more imperfect humans won't humanity eventually end up in the same place it was before the extinction?..