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The
noble houses of Europe have repeatedly intermarried, forming a political,
as opposed to a geographic or a religious, isolate. Ferdinand and Isabella
of Spain, for instance, were second cousins, but the houses of Aragon and
Castile, to which they respectively belonged, had previously intermarried
so often that the royal couple's cumulative coefficient of kinship was
much higher than one-sixty-fourth. One of their daughters-Joan the Mad-was
insane. Contrary to widely held belief, however, inbreeding has had nothing
to do with the "royal hemophilia" that has so far afflicted nine male descendants
of Queen Victoria, including the Czarevitch Alexis Romanoff and an uncle
of the present King of Spain, the Prince of the Asturias, who hemorrhaged
to death after a car accident in 1938. The disorder sprang from a genetic
mutation that is believed to have occurred in the X chromosome of Queen
Victoria's father, Edward, the Duke of Kent; it was inherited by one of
her four sons and by two of her four daughters. Prince Edward was fifty-one
when Victoria was conceived, and the germ cells of older men are more prone
to some types of mutation. The execution of Czar Nicholas and his family
and the untimely death of two afflicted Prussian princes have terminated
Victoria's Hesse line, but the mutant gene may still be carried by some
of her English and Spanish female descendants.
Defective
children of the European royalty and nobility were no doubt rarely seen
in public. The British anthropologist Francis Galton wrote in the last
century that "a large number" of victims of what he called "hereditary
silliness" were kept out of sight by their families, although their existence
was "well known to relatives and friends." One striking-though possibly
apocryphal-case of sequestration is related in a book called "Royal Scotland,"
by the genealogist Sir lain Moncreiffe of that Ilk and the writer Jean
Goodman. The first son of Lord Glamis is said to have been born, early
in the last century, "in a hideous form with a massive body covered with
matted black hair, tiny arms and legs, and a head sunk deep into his barrel
chest." The authors continue, "Obviously such a creature could not inherit
the title [the Earl of Strathmore] and he was kept in a secret room [in
Glamis Castle, the setting of "Macbeth"] and exercised on the roofs at
night. He was believed to have lived to be well over a hundred and died
in the early part of this century. To keep the dreadful secret only four
men at any one time were allowed to know of the Monster's existence. They
were the Earl, the family lawyer, the agent to the estate, and the eldest
son, who was shown the Monster, the rightful Earl, on the day that he came
of age."
Inbreeding
levels are sensitive to political and technological change. At the beginning
of the nineteenth century, for instance, after the Napoleonic code had
abolished primogeniture in Continental Europe, first-cousin marriage increased
in Italy as a means of keeping property in the family. But on the whole
inbreeding has not been a problem in Catholic countries, because of the
Church's promulgation of "forbidden degrees" of consanguinity. Since the
end of the nineteenth century, with the diffusion of local populations
brought about by the Industrial Revolution, there has been a decrease in
consanguineous marriage.
The world
is becoming increasingly panmictic-a healthy development both medically
and sociopolitically.
"The human
species is young, perhaps not more than 10,000 generations old, and the
major geographical races diverged from each other about 1,500 generations
ago, at most," the population geneticist Richard Lewontin writes in his
book "Human Diversity." "If anything is clear about the direction of human
evolution, it is that the early differentiation of people into local groups,
while still very much a part of our biological diversity, is on the decline.
The unifying forces of migration and of common selection through common
environment and common culture are stronger than they have ever been."
Most geneticists are in agreement that, as the science writer Guy Murchie
has put it, "no human. . . can be less closely related to any other human
than approximately fiftieth cousin, and most of us . .. are a lot closer.
The family
trees of all of us, of whatever origin or trait, must meet and merge into
one genetic tree of all humanity by the time they have spread into our
ancestors for about fifty generations." The "family of man," which has
been posited by many religions and philosophies (it was a central concept
of the Enlightenment, for instance), actually exists.
All it
takes for widely divergent populations to merge genealogically is migration
by one person. "A single indirect genetic contact between Africa and Asia
in a thousand years can make every African closer than fiftieth cousin
to every Chinese," Murchie has observed. "Surprisingly, this may happen
without any natives of either continent doing any particular traveling
at all, but simply in consequence of the wanderings of nomads in intermediate
territory." History can be seen, in other words, as a mosaic of billions
of overlapping pedigrees. The kinship group to which we all belong extends
indefinitely in every direction. Some genealogists have started to play
with this notion. The new vogue in genealogy is horizontal genealogy. By
charting the overlap in the pedigrees of recent American political figures,
for instance, the genealogist William Addams Reitwiesner has discovered
that the former White House aide Hamilton Jordan and former Florida Governor
Reubin Askew are eighth cousins once removed; that former President Jimmy
Carter and former President Richard Nixon are sixth cousins (both are descended
from aNew Jersey Quaker named Richard Morris, who lived before the American
Revolution); that Nixon and Vice-President George Bush are tenth cousins
once removed; that Bush is a seventh cousin of Elliot Richardson, Attorney
General in the Nixon Administration, and is also a kinsman of Ernest Hemingway
and of the nineteenth -century plutocrat Jay Gould; and that California
Senator Alan Cranston has in his constellation of known kin-through descent
from a man named Robert Bullard, who lived in Watertown, Massachusetts,
in the early seventeenth century-Queen Geraldine of Albania, Richard Henry
Dana, Emily Dickinson, George Plimpton, the Dows of Dow Chemical, Julie
Harris, and Margaret Mead.
The extent
of our kinship is brought home even more dramatically, however, by traditional,
vertical genealogy. "It is virtually certain. . . that you are a direct
descendant of Muhammad and every fertile predecessor of his, including
Krishna, Confucius, Abraham, Buddha, Caesar, Ishmael and Judas Iscariot,"
Murchie writes. "Of course, you also must be descended from millions who
have lived since Muhammad, inevitably including kings and criminals, but
the earlier they lived the more surely you are their descendant." The political
implications of this great kindred are quite exciting. If all of us could
be made aware of our multiple interrelatedness, if the same sort of altruism
that usually exists among close kin could prevail through the entire human
population, if this vision of ourselves could somehow catch on, then many
of the differences that have polarized various subpopulations from the
beginning of human history-differences that are for the most part the result
of adaptation to disparate climate, of genetic drift, and of cultural vagary
would seem secondary. The problems we have with each other would. become,
as it were, internal.
HOW big
is the human family?
We know
that close to five billion people are alive today, but how many have there
been in the past? According to the most carefully reasoned estimates, between
sixty-nine billion and a hundred and ten billion people have lived since
the appearance of human beings. The figures are based on an exponential
growth curve interpolated between "benchmark estimates," or key points
at which there are data related to the size of the world's population;
the disparity is the result of differences in estimated birth rates and
life spans and in the date of origin for "humans." Although the
ascent of the curve is at first-and
for many millennia-so gradual that it is largely lost in the thickness
of the draftsman's pen, the final tally is significantly affected by when
one decides to begin the curve. Creationists, who start the human race
with the placing of Adam and Eve in the Garden of Eden six thousand years
ago, and who believe that in about 2400 B.C. a worldwide flood killed off
everybody then alive except Noah and his family, come up with a considerably
lower figure for the total number of people ever-fifty-one billion. Most
historical demographers, however, begin their
curves a million years ago. Erect
hominids-the australopithecinesare thought to have lived as long as four
million years ago; the genus Homo is perhaps two million years old; archaic
Homo sapiens lived around three hundred thousand years ago; and our race,
Homo sapiens sapiens, begins to appear in the fossil record only about
a hundred thousand years ago. So the choice of a million years ago is something
of a compromise. The biologist Edward S. Deevey, Jr., has estimated that
between a million years ago and twentyfive thousand years ago a total of
thirty-six billion Paleolithic hunter-gatherers lived, in generations averaging
twenty-five years in length. Ten thousand years ago-the consensus date
for the beginning of settled agriculture-the world's population was a little
over five million. The figure is based on a study of the territorial requirements
of contemporary huntergatherers and on an estimate of the amount of land
available for human exploitation-an estimate based, in turn, on geological
evidence of the extent of the ice caps and on a reconstruction of the prevailing
climate and rainfall patterns. By the beginning of the Christian era, when
most people had become village farmers or city dwellers, the population
had risen to between two hundred million and four hundred million. This
slightly more informed guess, the demographer Ansley J. Coale explains,
is based on surviving information about censuses within the Roman Empire,
on imperial Chinese records, on a "tenuous estimate" by historians of the
population of India around then, and on a "crude allowance for the number
of people in other regions."
The growth
rate of a population is the difference between its birth rate and its death
rate, and, beginning about 1750, the start of the "modern era" (which represents
only twotenths of one per cent of human history), a number of developments
combined to reduce mortality in the West, thus causing comparatively unrestrained
growth. By 1750, of course, there were much more extensive written records,
and the world's population at that time can be estimated with twenty per
cent accuracy to have been around eight hundred million. The curve, which
for thousands of years has shown little more upward mobility than a straight
horizontal line, now begins to rise steeply. "To begin with," Coale recently
told me, "there was a more abundant and more regular supply of food, because
of an extension of cultivation, particularly in America; because foods
from the New World-potatoes and maizehelped to cause an agricultural revolution
in Europe; and because transport improved. Water supplies were cleared
up, and sanitary habits changed-people, including doctors, started to bathe
and to wash their hands more regularly. By 1825, medical innovations, such
as smallpox vaccine, had begun to have an effect. Doctors stopped healing
their patients by bleeding and purging, and in the latter part of the nineteenth
century germs were discovered and anesthetics were invented. Real curative
medicine did not begin until after 1930, with chemotherapy and antibiotics.
The reduction in mortality affected growth in two ways: by prolonging life,
it led to a larger population from a given stream of births, and by allowing
more women to survive to procreative age it enlarged the stream of births."
By the
late nineteenth century, between seventy-five and eighty-five per cent
of the women in the industrialized countries were surviving to the mean
childbearing age of twentyeight. (This is about the current proportion
in many parts of the Third World.) Coale estimates that until 1750 the
average woman, over the span of her childbearing years, had six offspring,
with the male-female ratio of the children about even, but that only one
of the three daughters survived to become a parent herself. The early deaths
not only depress the annual growth curve but figure, more significantly,
in the computation of the total number of people born. Since 1750, the
growth rate of the world's population has risen from .56 per thousand to
more than seventeen per thousand (with almost forty per thousand in prodigiously
fertile Kenya), and the world's population now stands at about four billion
seven hundred million people. Nearly a billion of these people were born
after 1970, and between four and seven per cent 43 of all the people who
have ever lived are alive today.
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