adopted children tended to conform to the lifestyle predicted by their biological parents, not their adoptive parents, in regards to crime and income (which implies some uncomfortable ideas about poverty and class).

The Blank Slate by Steven Pinker touches on this a lot. Pinker basically throws out most studies that don't control for genes (ie. You read to your kid and he develops good verbal skills.. But was that because you read to him/her, or because he inherited the genes that give good verbal skills), and instead he focuses on studies with adopted children.

Turns out that they are a lot more like their biological parents than their adoptive parents, and that twins that have been separated and adopted are still very similar to one another despite having grown in a different environment.

But Pinker mostly looked at psychological attributes, not at physical bodies.