I take no stance on the Ashkenazi IQ research presented here, but I did find this stretch interesting:
The possibility that Jewish mothers produce smarter children is unlikely in light of abundant evidence that families have no lasting effect on intelligence. Siblings reared together are no more correlated in IQ than siblings who were separated at birth, and adopted siblings are not correlated at all. Growing up in a given home within a culture seems to leave no lasting stamp on intelligence.
Really? “No lasting effect on intelligence”? In other words, drop a given newborn in a crackhouse or in the lap of luxury and it has no lasting effect on IQ? Unless the “within a culture” caveat means that one particular crackhouse has no greater or lesser impact on IQ than any other crackhouse.
In any event, since a given parent can have an enormous impact on a child’s academic performance in school, I suppose this points to the yawning gap between intellectual potential and intellectual performance. In its parents-don’t-matter approach, it reminds me a bit of this Gladwell piece from 1998 on the comparative importance of peers over parents in child development.