The thing about the smaller population is true to an extent. It will lead to more mutations via DNA, could possibly be missense, deletion, or even nonsense mutations. However, mutations are mostly bad as a blanket statement. There are some good ones here and there. Even though I'm religious, I'm letting my religion take a backseat to recorded observations and tried and true hypotheses. It's really weird, biology. It's a great general field to study, but it's also very complicated and can't really be summed up in one sentence. 10000 characters on here would easily scratch the bare surface, but that would be with too much summation and not enough detail.