A recent conversation with a friend sent me to find another, The Mountain of Names: A History of the Human Family, by Alex Shoumatoff, in a basement bookcase. Shoumatoff has been called "the greatest writer in America" by Donald Trump, but I don't think it is fair to hold that against him.
The Mountain of Names was published in 1985, but is still in print, which says something about it. In a chapter called The Kinship of Mankind Shoumatoff talks about the shape of our pedigrees. We are all used to seeing a family tree that begins with one person, and above that, two parents. And above each parent, two parents, so that the original person has four grandparents, eight great-grandparents, and so on. By the time we get back ten generations, we've got 1,024 ancestors in one generation! And then they really get going! Go back another 10 generations, and we've got about a million ancestors in that generation. We don't need to get back to Roman times before we realize there's something wrong: we have more ancestors than there were people alive at that time. Shoumatoff explains what happens:
Each time cousins marry, duplication occurs in their descendants' pedigrees, because as cousins they already occupy a lot there. The farther back one traces any person's genealogy the greater the rate of duplication grows, until finally, when there is more cousin intermarriage than input from new people, the shape of one's pedigree stops expanding and begins to narrow. Each person's complete family tree, in other words, is shaped like a diamond. In the beginning it expands upward from him in an inverted triangle.... At some point, hundreds of years back, the rate of expansion peaks; the base of the inverted triangle is reached and, overwhelmed by "collapse," the pedigree starts to narrow again, eventually coming to a point at a theoretical first couple, "Adam and Eve."Two more quotes from the book:
The pedigree of Prince Charles has probably been as exhaustively researched as anybody's.... In the seventeenth generation of his pedigree, for instance, when he should theoretically have 65,536 progenitors, cousin intermarriage has deprived him of all but about twenty-three thousand ... of which [Robert C.] Gunderson has identified only twenty-eight hundred.... Of these twenty-eight hundred, Gunderson has discovered that "at least two thousand" of the descents are from the same person: Edward III, who ruled England from 1327 to 1377.and
All Americans with British ancestry are probably descended from Edward III.You can call me "Sir Sempringham." Or how about "Lord Sempringham." I like that. It has a nice ring to it.