We've needlessly turned parenting into an unpleasant chore. Parents invest more time and money in their kids than ever, but the shocking lesson of twin and adoption research is that upbringing is much less important than genetics in the long run. These revelations have surprising implications for how we parent and how we spend time with our kids. The big lesson: Mold your kids less and enjoy your life more. Your kids will still turn out fine. Selfish...