AMERICANS cherish the idea of the meritorious self- made man.  “A man who makes boast of his ancestors doth but advertise his own insignificance,” Benjamin Franklin, the original self-made man, once wrote. The sentiment has stuck. Merit makes sense to us intuitively, and is almost demanded by our political principles. Jefferson’s “natural aristocracy,” the rule of the worthy, is what we strive for. In spite of this, as Adam Bellow shows in his provocatively titled In Praise of Nepotism: A Natural History,† Americans’ meritocratic instincts are not absolute.  Bellow contends that Americans are more comfortable with nepotism than our republican and egalitarian principles commonly have us presume, and he devotes the better part of his book to explaining how and why.