some strange stuff on genetics by steven pinker in TNR

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Jul 31, 2007, 5:01:05 PM7/31/07

The Genealogy Craze in America.
Strangled by Roots
by Steven Pinker 1 | 2
Post date 07.30.07 | Issue date 08.06.07 Discuss this article
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Few technologies often have unforeseeable consequences. Michael
Faraday could not have anticipated the rise of the electric guitar and
its effects on our culture, nor did the inventors of the laser realize
they had laid the ground for a thriving industry of tattoo removal.
And it is safe to say that Watson and Crick could not have foreseen a
day when an analysis of Oprah Winfrey's DNA would tell her that she
was descended from the Kpelle people of the Liberian rainforest. "I
feel empowered by this," she said upon hearing the news, overcoming
her disappointment that her ancestors were not Zulu warriors.

A fascination with ancestry has long been part of the human condition,
from the "begat's" of the Bible to the Roots miniseries and the
restoration of Ellis Island. But with the advent of the Internet and
genomic technology, genealogy has entered a new age. The past year has
served up a series of high-profile revelations. The news that Barack
Obama's ancestors owned slaves was a bit more surprising than the news
that Strom Thurmond's did, but it was more surprising still to be told
that among the Thurmond family's slaves were the ancestors of Al
Sharpton. And Henry Louis Gates Jr., the host of the fascinating PBS
series African American Lives, which explored the family trees of six
prominent African Americans, was astounded to learn that half of his
own ancestry was European, including Irish kinsmen on his father's
side and two Jewish women on his mother's.

Few of us can expect that a search for ancestors will bring us an
inheritance, a title, or a coat of arms: the rewards of genealogy are
mostly psychological. As Winfrey put it, "Knowing your family history
is knowing your worth." The sentiment, though, is dubious--not just on
moral grounds but on biological ones. A closer look at the human drive
to know one's family tree uncovers a number of tensions between our
intuitions of kinship and the facts of kinship. Some of those facts
show that the findings of the new genealogy should not have been
surprising at all. And others, tacitly appreciated for millennia, have
recently been neglected to our peril.

For all its fascination, kinship is a surprisingly neglected topic in
the behavioral sciences. A Martian reading a textbook in psychology
would get no inkling that human beings treated their relatives any
differently from strangers. Many social scientists have gone so far as
to claim that kinship is a social construction with no connection to
biology. But assuming the creationists are wrong and humans are
products of evolution, it would be surprising if our species entirely
escaped the powerful forces that shape organisms' behavior toward
their kin. Genetics and evolutionary theory predict that the biology
of kinship should have biased our thoughts and emotions about
relatives in several ways.

The first is the simple fact that blood relatives are likely to share
genes. To the extent that minds are shaped by genomes, relatives are
likely to be of like minds. Close relatives, whether raised together
or apart, have been found to be correlated in intelligence,
personality, tastes, and vices. The discovery of an ancestor is thus
felt to reflect on the descendant, who may feel he has an explanation
for the kind of person he is, and who can claim to have a dose of the
ancestor's praiseworthy traits. A promotional spot for Coca-Cola in
African American Lives juxtaposes footage of African Americans with
images of traditional Africans and says, "She has her great-great-
great-grandmother's eye for adornment. He is fit and agile, like his

The similarities among blood relatives mean that they are likely to
share values, and shared values can lead to easy solidarity because of
what ecologists call mutualism and economists call positive
externalities. A pair of associates with the same interests can
benefit each other just by being selfish--always the most painless
route to altruism. If two roommates have similar tastes in music, each
will benefit the other every time she brings home a new CD, and each
has a reason to value the other's well-being. To identify a blood
relative, then, is to identify a potential soul mate. Adoptees who
track down their biological parents and siblings often report an
instant solidarity as they quickly discover shared quirks and

A more direct tug of shared genes on family emotions comes from the
phenomenon that biologists call inclusive fitness, kin selection, and
nepotistic altruism. The overlap of genes among relatives does more
than make them similar; it alters the dynamics of natural selection.
Over evolutionary time, any gene that predisposed a person to be nice
to a relative would have had some chance of helping out a copy of
itself inside that relative, and the gene would have been favored by
natural selection and entrenched in the genome (as long as the average
benefit to the relative, discounted by the probability that the gene
is shared, exceeds the average cost to the favor-doer). A sharing of
genes at the genetic level sets the evolutionary stage for feelings of
solidarity and affection at the emotional level, and that in turn
shapes much of human life. In traditional societies, genetic relatives
are more likely to live together, work together, protect each other,
and adopt each other's orphaned children, and are less likely to
attack, feud with, and kill each other. Even in modern societies,
which tend to weaken ties of kinship, studies have shown that the more
closely two people are genetically related, the more inclined they are
to come to each other's aid, especially in life-or-death situations.

Solidarity between pairs of relatives is further amplified by the fact
that they have other relatives in common. My brother and I are close
not just because each of us has copies of genes in the other, but
because we share a mother, a father, a sister, and nieces and nephews,
so our genetic interests are yoked together. This triangular altruism
also explains why non-blood relatives can feel various degrees of
affinity--most dramatically in the case of a husband and wife, whose
long-term genetic interests are fused in their children, and to a
lesser extent in the case of step- siblings and in-laws, as long as
they are not in zero-sum competition for the common relative's
affections or resources.

But now comes a crucial bit of arithmetic. In sexually reproducing
species, every organism has two parents, and every organism makes up
half the parentage of each of its offspring. The result is that as
people are separated by more generations, they are related to an
exponentially greater number of people, and their genetic relatedness
to any of them plummets, also exponentially. Going upward, you have
two parents, with whom you share half your genes apiece; four
grandparents, with whom you share one-quarter; eight great-
grandparents; sixteen great-great-grandparents; and so on. Going
downward, if you and your descendants have two children apiece, then
you'll have four grandchildren, eight great-grandchildren, and so on.
And going sideways, you share half your genes with your sibling, one-
eighth with each of your first cousins, one-thirty-second with each of
your second cousins, and so on.

Exponential functions quickly explode to unimaginable magnitudes or
peter out to infinitesimal ones, and the inability of our intuition to
keep track of them leads to many paradoxes of kinship. In an old
Smothers Brothers routine, Tommy explained why the population
explosion is a myth. We have two parents, he noted, and four
grandparents, eight great-grandparents, sixteen great-great-
grandparents, and so on. The further back you go, the more ancestors
you have. So, he concluded, "The pop- ulation isn't growing--it's
tapering off!" Like many of their jokes, this one depends on a subtle
truth. If you assume twenty-five years per generation, you can
calculate that you had around three billion ancestors at the time of
the signing of the Magna Carta, one hundred billion during the Norman
invasion, two quintillion at the fall of the Roman Empire, and around
1,200,000,000,000,000,000,000,000 at the birth of Jesus. Needless to
say, the Earth did not contain a fraction of that many people in those

The paradox is resolved by the realization that our ancestors must
have married their cousins of various distances and removes, so that
vast numbers of the slots in one's family tree are filled by the same
individuals. Imagine, in an extreme case, that your parents were first
cousins. Then two of your great-grandparents on your mother's side
would also be your great-grandparents on your father's side--you would
have six great-grandparents instead of eight. Genealogists call this
"pedigree collapse": the necessity that as you trace your family tree
backward, it will fan out for a number of generations until it begins
to encompass most of the people in the available population, whereupon
it falls back on itself, coinciding with the original growth of that
population. The rate of collapse depends on the size of the pool of
potential mates and the average rate and closeness of cousin
marriages. But the fact that our ancestors never covered the surface
of the Earth ten deep shows that medium-distant-cousin marriages must
have been the rule rather than the exception over most of human
history. This chronic incest, by the way, did not turn our ancestors
into the cast of Deliverance. The degree of relatedness, and hence the
risk that a harmful recessive gene will meet a copy of itself in a
child, falls off a cliff as you move from siblings to first cousins to
more distant cousins.

The same arithmetic that makes an individual's pedigree collapse onto
itself also makes everyone's pedigree collapse into everyone else's.
We are all related--not just in the obvious sense that we are all
descended from the same population of the first humans, but also
because everyone's ancestors mated with everyone else's at many points
since that dawn of humanity. There aren't enough ancestors to go
around for everyone to have a family tree of his or her own. So it is
a mathematical necessity, not a surprise, that genealogy will turn up
strange bedfellows. George W. Bush is a distant cousin of his
electoral opponents Al Gore and John Kerry (as well as of Richard
Nixon, Ernest Hemingway, Queen Elizabeth, and, through her, every
European monarch). Gore, for his part, is a descendant of Charlemagne,
and Kerry is a descendant of Mary, Queen of Scots--and presumably also
(thanks to his recently-discovered-to-be-Jewish paternal grandfather)
of rabbis, cantors, and medieval moneylenders. This brings up another
corollary of the mathematics of kinship: a single mating between
people from two ethnic groups results in all their descendants being
related to both groups in perpetuity. So even occasional couplings
across racial and ethnic lines can entangle family trees, explaining
why humans, that peripatetic and sexually omnivorous species, are
genetically fairly homogeneous, despite our worldwide distribution.

The genealogical ties connecting American presidents and European
royalty are not a sign of some vast transatlantic ruling caste. Every
noteworthy person is related to other noteworthy people (together, of
course, with countless not-so-noteworthy people). One genealogist with
too much time on his hands showed that the late Senator Alan Cranston
was related to Emily Dickinson, George Plimpton, Margaret Mead, the
actress Julie Harris, the Dow family of chemical fame, and Queen
Geraldine of Albania. Another discovered that Tom Hanks, the star of
The Da Vinci Code, has blood ties with many of the historical figures
mentioned in the film, including William the Conqueror, Shakespeare,
and Henry VIII. Also recently revealed is the fact that Paris Hilton
is related to fellow celebrity jailbirds Zsa Zsa Gabor and G. Gordon
Liddy. Finding kinship ties among famous people is shooting ducks in a

And before you brag about the talent or courage you share with some
illustrious kinsman, remember that the exponential mathematics of
relatedness successively halves the number of genes shared by
relatives with every link separating them. You share only 3 percent of
your genes with your second cousin, and the same proportion with your
great-great-great-grandmother. It is important to remember that
psychological traits are nowhere near completely heritable in the
first place, so the chances that you got your eye for adornment from
that ancestor in the gorgeous dashiki are rather small. Do not expect
genetically inspired largesse from the rich relative uncovered by your
genealogy service, either. A gift from a second cousin would have to
result in a thirty-two-fold increase in the number of your surviving
descendants compared to his for a desire to bestow it upon you to have
evolved. The relentless decimation of resources (both genetic and
financial) across generations is the rationale behind the feudal
practice of primogeniture, in which all the family estate was
bequeathed to the eldest son. And it is why in modern times family
fortunes can dissipate so quickly--"three generations from
shirtsleeves to shirtsleeves," as Nicholas Murray Butler put it.

The geometric decay of relatedness also takes some of the fun out of
two of the main tools used by genetic-ancestry services: the analysis
of mitochondrial DNA (which is passed from mother to daughter) and of
Y-chromosomes (which are passed from father to son). Since they trace
ancestry only through the all-female or all-male branch of your family
tree, they can identify only one tendril, which diminishes
exponentially the further back you go. Winfrey's mitochondrial DNA
does not show that she is a Kpelle, but rather that she is one-sixty-
fourth (or perhaps even 1/128th or 1/256th) Kpelle. Many African
Americans who seek their paternal ancestor, and therefore a sense of
their African roots, via Y-chromosome analysis discover to their
dismay that this root lies in Germany or Scotland.

If family ties are so biologically tenuous, why does kinship loom so
large in the human psyche? One reason is that our intuitions about
kinship evolved when we lived in villages and bands whose small size
and limited mobility ensured that most marriages were between closer
cousins, and hence the genetic overlap between relatives was close
enough to be biologically significant. Today we project these feelings
of affinity onto relatives who are far more distant--indeed,
arbitrarily distant, thanks to the wonders of Internet and DNA

But the other reason is that our sense of kinship is triggered not by
relatedness itself, but by the perception of relatedness. After all,
when we encounter a possible relative, we generally do not demand a
cheek swab and analyze its DNA. Instead we rely on cues that in the
evolutionary past tended to correlate with relatedness. Recent
experiments by Debra Lieberman, John Tooby, and Leda Cosmides have
shown that two kinds of life experience are crucial in triggering
family feelings toward siblings (such as doing them favors and being
willing to donate a kidney to them). One consists of observing the
sibling being cared for by one's mother when it was an infant. The
other is having grown up in the same household as the sibling. That is
why children adopted at birth can be emotionally close to their
parents and siblings despite the lack of genetic overlap: the early
close association sets off everyone's kinship detectors, a kind of
benign illusion. And because these experiences also trigger repugnance
at the thought of having sex with the relative, incest avoidance is
not perfectly correlated with biological relatedness. Unrelated
children who are brought up together (like nursery-mates in kibbutzim)
tend to shun each other as sexual partners in adulthood, as if they
were siblings. And children who meet a parent or sibling for the first
time in adulthood can find him or her sexually attractive, as the
novelist Kathryn Harrison recounted in The Kiss, her memoir of a four-
year affair with her father.

When it comes to individual people, then, kinship is in the mind of
the beholder. That creates an opening through which manipulators can
flood people's kinship sense with cues that mimic the signals of
biological relatedness. This kind of mind control is a strong
temptation to anyone who wants to foster cohesion among people who are
not closely related. Contrary to a shibboleth of the American right,
family values do not uphold religion and country; they subvert them.
An extended family is a rival coalition to any other group, held
together not by an ideology or social contract or common purpose but
by brute genetic relatedness. And it is a coalition with an unfair
advantage: relatives care for one another more than comrades do.
Religions and political movements thus have to undermine family
loyalties. Marxist collectivization and Moonie programming are obvious
recent examples, but millennia before them Jesus momentously declared,
"A man's foes shall be they of his own household. He that loveth
father or mother more than me is not worthy of me: and he that loveth
son or daughter more than me is not worthy of me."

Successful coalitions often try to co-opt family feelings by tricking
the brain into perceiving the coalition as kin. Though the most potent
technique--forcing people to grow up in a single household--is
impractical, other kinds of kinship illusion have repeatedly been
invented. The anthropologist Alan Fiske notes that communal meals are
one of the most common bonding rituals the world over, partly because
they simulate family experiences, partly because people believe that
you are what you eat, and so if you eat the same stuff you are the
same stuff. Many tribes and coalitions (such as the Mafia) cut their
fingers and rub them together to allow their blood to mingle, hence
the expression "blood brothers." People also disfigure their bodies--
by scarring, tattooing, piercing, hairstyling, and circumcision and
other forms of genital mutilation--as if to make the group look like a
separate race or species, biologically distinct from other human

Language provides another way to co-opt the warm and fuzzy feelings
people have toward their relatives. One common trick is the use of
kinship metaphors: brethren, brotherhood, fraternity, sisterhood,
sorority, the fatherland, the mother country, the family of man, and
so on. These tactics are provably effective: experiments have shown
that people are more convinced by a political speech if the speaker
engages them with the language of kinship. Myths and ideologies are
also commonly put to use. People are told that they are descended from
a patriarch or a primeval couple, or that they are connected to a
natal land, or that they came into being in the same act of creation,
or that they are related to the same totemic animal.

In large part, the institutions of modernity depend on a dissolution
of family ties. It is hard to run an effective organization if you
cannot fire the knucklehead brother-in-law forced on you by your
wife's family, nor can civil society function if the instruments of
government are treated as the spoils of the most powerful local clan.
Public safety is more effectively guaranteed by a disinterested police
and court system than by a threat that your male relatives will avenge
your murder, and national defense above all depends on the willingness
of citizens to neglect the bonds of kinship. In The Godfather: Part
II, Sonny Corleone upbraids Michael for his sympathy with the men who
enlisted after Pearl Harbor: "They're saps because they risk their
lives for strangers. Your country ain't your blood. Remember that."

In the struggle between society and family, the exponential
mathematics of kinship ordinarily works to the advantage of society.
As time passes or groups get larger, family trees intertwine,
dynasties dissipate, and nepotistic emotions get diluted. But families
can defend themselves with a potent tactic: they can graft the twig
tips of the family tree together by cousin marriage. If you force your
daughter to marry her first cousin, then your son-in-law is your
nephew, her father-in-law is your brother, your parents' estate will
be worth twice as much per grandchild, and the couple will never have
to bicker about which side of the family to visit on holidays. For
these reasons, clans and dynasties in many cultures encourage first-or
second-cousin marriage, tolerating the slightly elevated risk of
genetic disease. Not only does cousin marriage amplify the average
degree of relatedness among members of the clan, but it enmeshes them
in a network of triangular relationships, with kinsmen valuing each
other because of their many mutual kin as well as their own
relatedness. As a result, the extended family, clan, or tribe can
emerge as a powerfully cohesive bloc--and one with little common cause
with other families, clans, or tribes in the larger polity that
comprises them. The anthropologist Nancy Thornhill has shown that the
prohibitions against incestuous marriages in most societies are not
public-health measures aimed at reducing birth defects but the
society's way of fighting back against extended families.

In January 2003, during the buildup to the war in Iraq, the journalist
and blogger Steven Sailer published an article in The American
Conservative in which he warned readers about a feature of that
country that had been ignored in the ongoing debate. As in many
traditional Middle Eastern societies, Iraqis tend to marry their
cousins. About half of all marriages are consanguineous (including
that of Saddam Hussein, who filled many government positions with his
relatives from Tikrit). The connection between Iraqis' strong family
ties and their tribalism, corruption, and lack of commitment to an
overarching nation had long been noted by those familiar with the
country. In 1931, King Faisal described his subjects as "devoid of any
patriotic idea ... connected by no common tie, giving ear to evil;
prone to anarchy, and perpetually ready to rise against any government
whatsoever." Sailer presciently suggested that Iraqi family structure
and its mismatch with the sensibilities of civil society would
frustrate any attempt at democratic nation-building.

Outside a small family circle, the links of kinship are biologically
trifling, vulnerable to manipulation, and inimical to modernity. For
all that, the almost mystical bond that we feel with those whom we
perceive as kin continues to be a potent force in human affairs. It is
no small irony that in an age in which technology allows us to indulge
these emotions as never before, our political culture systematically
misunderstands them.

Steven Pinker is Johnstone Family Professor of Psychology at Harvard.
His new book, The Stuff of Thought: Language as a Window Into Human
Nature, will be published by Viking in September.


Jul 31, 2007, 7:36:22 PM7/31/07
What did you find strange about the article? It's overlong,
tediously written, and comes to rather dubious conclusions,
but that just puts it in the mainstream.

On Jul 31, 5:01 pm, to see or not to see <>


Jul 31, 2007, 7:55:18 PM7/31/07
I feel empowered by the fact that I have no eggplant in my genome.

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