There definitely could have been changes, but yeah I guess we have to learn to live with it without going postal.

Sometimes children are pretty much predestined to not become very smart because both their parents weren't very smart or think of situations like children born from incestuous relationships and so on. Still, it's in neither case guaranteed that the children inevitably will become stupid.

By the way, for those people that still demand half-monkeys, fish-people and what not for proof of evolution, I'd recommend reading; Shubin's "Your inner fish". It was written in 2008 and is both interesting and a good read.