> Eventually the genes
> for criminal tendencies would be weeded out of the population by natural
> selection.
It's my understanding that no genetic link has ever been found for criminal behavior; indeed, if there were, Australia wouldn't be one of the most law abiding nations in the world. (Please correct me if I've missed something; in particular, I wouldn't be surprised if there is a gene for sociopathy.)
In the US, there is an available adoptive home for every child currently in foster care, but the law currently will not permit adoption as long as there is a ghost of a chance that an abusive or addicted parent might, some day, be able to care for a child. Allowing children to get out of the notorious foster care system sounds like a good start for preventing crime.