I've always wondered something; Wouldn't many people in earlier history (medieval times, colonial era, etc.) have been born with fetal alcohol syndrome or other complications, due to alcoholic beverages being one of the few safe things to drink?
This question has already been answered a few times, with the best answer I could find being found here.
Basically it all comes down to the fact that although alcohol was drank often, it was not the alcohol we think of today. They "typical" beer would have been around 1-3%.
Also, here is another post that explains how the whole "alcohol being the only safe thing to drink" concept may in fact not have been true for most.