There's something interesting about endangered animals, some that shrink down to only a few hundred, and then grow back to population sizes that can be reintroduced. Wouldn't they have an insane amount of defects due to close interbreeding and go extinct?
Well it turns out when animal populations get that small, yes a huge number of births have large numbers of horrific birth defects and they die. But the ones that survive usually lack a lot of the really bad recessive traits. Animals in super low population do naturally shed bad recessive genes just due to statistical probability and the resulting generations can grow quite rapidly.