Children are the most malleable sorts of human beings. Do adopted children become the average of the family that adopts them?

How did you solve this problem?

A quote on the dangers of solving this problem, from The Bell Curve by Richard J. Herrnstein and Charles Murray (1994):

Think of your twelve closest friends or colleagues. For most readers of this book, a large majority will be college graduates. Does it surprise you to learn that the odds of having even half of them be college graduates are only six in a thousand, if people were randomly paired off? Many of you will not think it odd that half or more of the dozen have advanced degrees. But the odds against finding such a result among a randomly chosen group of twelve Americans are actually more than a million to one. Are any of the dozen a graduate of Harvard, Stanford, Yale, Princeton, Cal Tech, MIT, Duke, Dartmouth, Cornell, Columbia, University of Chicago, or Brown? The chance that even one is a graduate of those twelve schools is one in a thousand. The chance of finding two among that group is one in fifty thousand. The chance of finding four or more is less than one in a billion.

Most readers of this book – this may be said because we know a great deal about the statistical tendencies of people who read a book like this – are in preposterously unlikely groups, and this reflects the degree of partitioning that has already occurred. [...]

The point of the exercise in thinking about your dozen closest friends and colleagues is to encourage you to detach yourself momentarily from the way the world looks to you from day to day and contemplate how extraordinarily different your circle of friends and acquaintances is from what would be the norm in a perfectly fluid society. This profound isolation from other parts of the IQ distribution probably dulls our awareness of how unrepresentative our circle actually is. [...] When people live in encapsulated worlds, it becomes difficult for them, even with the best of intentions, to grasp the realities of worlds with which they have little experience but over which they also have great influence, both public and private.