HOLD FOR RELEASE: FRIDAY, FEB. 14,
1997, 10 A.M. PST
Contact: Roger Segelken
Office: (607) 255-9736
Internet: [email protected]
Compuserve: Larry Bernard 72650,565
http://www.news.cornell.edu
SEATTLE -- Some of the same evolutionary "predispositions" that held
together extended families for our hunter-gatherer ancestors -- and even
prototypical nuclear families until recently -- are partly to blame for
today's dysfunction, conflict and violence within fractured families,
according to a Cornell University biologist who studies heritable
adaptations in animal and human societies.
One such ancient, genetically programmed rule -- help your closely related
kin -- may have an ugly mirror-face when unrelated individuals become part
of the family, Stephen T. Emlen told an American Association for the
Advancement of Science (AAAS) session today (Feb. 14) on "Sexual
Differences in Mating Strategies: The Interface of Culture, Law and
Biology." Just as in many "lower" animals, human stepparents turn a
less-caring shoulder -- and occasionally even a violent one -- to children
who don't carry their genes, according to Emlen, the Jacob Gould Schurman
Professor of Biology at Cornell.
"The good news is we have the potential to largely overcome many of our
genetically influenced behavioral predispositions," Emlen said. "With
greater awareness and early detection, we can avoid detrimental behaviors,"
he said, suggesting a renewed role for grandparents and a policy change for
government.
Emlen's AAAS presentation, titled "The Evolutionary Study of Human Family
Systems," follows his publication of "15 Predictions of Living within
Family Groups" (Proceedings of the National Academy of Sciences, Aug. 29,
1995), which explains the evolutionary roots of behaviors ranging from
infanticide and sexually related aggression to multigenerational nurturing
during hard times.
More than 300 species of birds and 80 kinds of mammals are known to follow two
family-grouping predispositions that keep chip-off-the-old-block DNA in the
gene pool -- biparental care of offspring and multigenerational alliances
to help raise related young. So did most Homo sapiens until the latter
half of the 20th century.
"The helping individual receives indirect genetic benefits in direct
proportion to how closely it is related to the recipients of its aid. All
else being equal, the closer the kinship, the greater the tendency for
animals to cooperate," Emlen said, explaining the so-called kin selection
theory (and how the help-your-relatives rule became incorporated into our
genetic makeup) in an article prepared for the journal Social Science
Information.
Most nonhuman primate species are not useful models of family cooperation,
Emlen said, because long-term pair bonds are rare and male primates seldom
help care for infants. Among animal species showing heritable tendencies
for family organization are the lion; mongoose; marmoset; naked mole-rat,
which is studied by Emlen's colleagues at Cornell; scrub jay of Florida and
Mexican jay of Arizona; white-fronted bee-eater, which Emlen studied in
Africa for more than a decade; and acorn woodpecker. Even the common crow
helps parents raise younger siblings.
These heritable adaptations to family living were selectively advantageous
for life in ancestral (pre-agricultural, pre-industrial) extended families,
Emlen told the AAAS meeting. And most of the rules still worked as nuclear
families became the early-20th-century norm and extended families, more of
a rarity.
"Now, the nuclear family is becoming less common. It's being replaced by
increasing numbers of single-parent and stepparent families. At the same
time we are seeing an increase in child abuse, child delinquency and child
truancy," Emlen said.
When Emlen surveyed social scientists' reports, he found disturbing
correlations between family structure and the well-being of children.
Among them:
-- Stepchildren suffer much higher rates of physical abuse and even death
than children in intact families.
-- Stepparents invest less time and effort in the offspring from their
partner's previous marriage than they do with their own children.
-- Stepchildren are at greater risk for sexual abuse than children in
intact families, and stepparents are overwhelmingly the abusers. The
incidence of sexual abuse of stepdaughters in one study was eight times
that of biological daughters.
-- Children in stepfamilies leave home significantly earlier than children
in intact families.
-- Stepfamilies are less stable than intact families. The incidence of
subsequent divorce is higher in second marriages and increases with the
number of stepchildren present.
"The rules we evolved with don't work well in the greater diversity of
family types present today," Emlen said. "One could ask: 'Who cares about
predispositions? After all, we are conscious beings who can deliberately
change our behavior when we put our minds to it.' But we don't always have
the luxury of reacting rationally in certain situations."
That is where some awareness of our evolutionary legacy can help minimize
damage in the "new" social arrangements, the Cornell biologist suggests.
Emlen is not prepared to say there is a gene for helping kin or harming
others. But the human genome project offers an interesting analogy, he
says. Just as the discovery of genes for dispositions to disease enables
people to reduce other risks of contracting disease, knowing our behavior
predispositions can help us avert social conflict.
"Be aware that if you are in a stepfamily situation -- or if you are a
social worker dealing with stepfamilies -- there is a statistically greater
chance of problems," Emlen said. "We didn't ask for these biological
predispositions; they came with a genetic package that worked for our
ancestors for thousands of years. But, armed with knowledge and insight
from the evolutionary perspective, we can better identify likely
flashpoints of family conflict and use our intellectual resources to
consciously suppress those predispositions that negatively impact others."
The biologist also offers a way to turn predispositions to the family's
favor: Bring grandparents back into the child-rearing picture, especially
in single-parent families. Government agencies, he says, could assist by
offering tax incentives to grandparents who directly assist in rearing
grandchildren in need and to parents who wish to move closer to their
parents, or vice versa.
"All the studies of animal and human societies with extended family
arrangements predict that this would work," Emlen said. "Certainly,
grandparents of many species, including human, have a predisposition to
care for kin."
-30-
EDITORS: Stephen Emlen will participate in a AAAS news conference on Feb.
14 at 9 a.m. PST, Room 201 Seattle Convention Center. He will be at the
meeting Feb. 14 to 19 and can be reached at the Seattle Hilton (206)
624-0500. After Feb. 19 he will be at his Cornell office, (607) 254-4327,
e-mail
be reached in the AAAS newsroom or at the Sheraton Seattle, (206) 621-9000,
Feb. 13-18, or at (607) 255-3651 after that.
RSS