Baboons May Have Influenced Human Evolution
We may take
it for granted that humans can classify each other according
to familial or social status, but how did those abilities evolve? In
the November 14 issue of Science, Penn researchers reported
that, much like humans, baboons identify each other based on
complex rules that determine relationships between families
and status or "rank" within their particular family.
organize their knowledge of social relationships into a hierarchical
structure, and they also make use of hierarchical structures
when deducing relationships between words in language," said
Dr. Robert Seyfarth, professor of psychology, and one
of the study's authors. "The existence of such complex social
classifications in baboons, a species without language,
suggests that the social pressures imposed by life in complex
groups may have been one factor leading to the evolution of
sophisticated cognition and language in our pre-human ancestors."
the last 12 years, Dr. Seyfarth, Dr. Dorothy Cheney, professor
and their colleagues have studied a troop of more than 80 baboons
in the Okavango Delta of Botswana. Their research explores
the cognitive mechanisms that might be the basis of primate
social relationships and how such relationships may have influenced
the development of human social relationships, intelligence
baboons make threatening grunts, which lower-ranked baboons
answer with supplicating screams. The researchers tape-recorded
the calls of known individuals, then used a computer to mix
and match the grunts and screams to make it seem as if a lower-ranked
baboon was effectively dominating a higher ranked baboon.Then,
in a playback experiment, the researchers played recorded interactions
to individual baboons to see if there would be a response. Some
playbacks mimicked the existing hierarchy, whereas others mimicked
a rank-reversal, either between two members of the same family
or between two members of different families.
run counter to their expectations, and a baboon will momentarily
pause and give a look, just as you might if you didn't quite
believe what you had just heard," said Dr. Thore Bergman, postdoctoral
researcher in biology and lead author on the paper. "Our
results demonstrated that these relationships were real and
relevant to these baboons."
within families are surprising, but rank-reversals between
families are of potentially much greater importance and
we see that the baboons recognize the significance of these
events," Dr. Seyfarth said. "To do so, they must be astute
observers, watching animals interact and deducing a social
structure on the basis of what they've seen."
and Conductivity of Nanotube-Laced Materials
fortified with carbon nanotubes are strongest when the embedded
filaments run parallel to each other, but electronic and thermal
conductivity are best when the nanotubes are oriented randomly. That's
the finding from a team of engineers at Penn who have developed
a production technique that permits a finer and more precise
dispersion of nanotubes within a material.
results, which could give scientists the tools to customize
materials to meet their particular needs, are reported online
and in the December 15 print edition of the Journal of Polymer
Science Part B: Polymer Physics. Less than one-ten-thousandth
the width of a human hair, carbon nanotubes possess unparalleled
strength, superior heat-conducting properties and a unique
ability to adopt the electrical properties of either semiconductors
or metals, but so far they have failed to back up this theoretical
potential with real-world applications.
hurdle that has prevented us from mixing nanotubes into materials
to take advantage of these remarkable properties is their stubborn
tendency to bundle together," said Dr. Karen I. Winey, associate
professor of materials science and engineering. "Uniform dispersion
of nanotubes in materials is absolutely critical to harnessing
their strength, electrical conductivity and thermal stability."
and her colleagues used a technique called coagulation to mix
single-walled carbon nanotubes evenly into a plastic, or polymer,
called poly(methyl methylacrylate). In this method, nanotubes
and PMMA are first mixed into a solvent, creating a fine suspension,
and then plunged into distilled water. The PMMA rapidly
precipitates out of this mixture, dragging the nanotubes with
it and preventing them from clumping.
"At low concentrations
the electrical conductivity of these nanocomposites was roughly
100,000 times better when the nanotubes were unaligned than
when the nanotubes were well aligned," Dr. Winey said.
is an asset for some mechanical properties, alignment is clearly
a detriment for electrical properties," Dr. Winey said, "where
adding more of the expensive nanotubes is not nearly as cost-effective
as producing a random orientation of nanotubes in a composite." She
was joined in the research by Dr. John E. Fischer, professor
of materials science and engineering, and Fangming Du, a graduate
student in chemical and biomolecular engineering.
Transition to Adulthood Delayed
an adult takes longer today than in previous decades, with
many not achieving all the traditional markers--starting a career,
forming a new household, starting a family--until after age
30, according to a study by the Network on Transitions to Adulthood. The
Network, funded by the MacArthur Foundation, is directed by
Dr. Frank Furstenberg, professor of sociology.
to the study, a demographic shift has occurred, almost without
notice, but with important ramifications for the job market,
the marriage market and public policy. To examine the experiences
of youth as they move toward adulthood, Dr. Elizabeth Fussell,
a demographer at Tulane University, and Dr. Furstenberg used
1900-1990 U.S. Census data on youth aged 16-30 along with sample
data from the Census Bureau's 2000 Current Population Survey.
and Dr. Furstenberg's report The Transition to Adulthood
During the 20th Century: Race, Nativity and Gender includes
findings on the shifting path to adulthood for native-born,
foreign-born, white and black men, and women.
study's other findings:
results of the study are to be published in the forthcoming
the Frontier of Adulthood: Theory, Research, and Public Policy,
edited by Richard A. Settersten, Frank Furstenberg and Ruben
G. Rumbaut (University of Chicago Press).
Electronic Scale Lowers Mortality Rates
with advanced heart failure who reported daily to health-care
professionals any changes in weight or symptoms associated
with the illness had significantly lower mortality rates than
their unmonitored peers, according to a national study led
by investigators in the Heart Failure and Cardiac Transplant
Program at Penn's Medical Center. The findings were published
in the October issue of American Heart Journal.
findings were a surprise," said Dr. Lee R. Goldberg, assistant
professor of medicine, and principal investigator for the study. "We
set out to determine whether the rate of hospitalization for
patients who reported their weight and symptoms to health-care
personnel on a daily basis might be lower than the rate for
unmonitored patients. Instead, we found the hospitalization
rates were essentially the same for both groups--but there was
a striking disparity in their mortality rates over the period
of the study."
six months, the nurse-monitored group sustained 11 deaths,
while the unmonitored group sustained 26 deaths--a 56 % difference
in mortality rates. Dr. Goldberg said the impact on mortality
was demonstrated despite "aggressive medical management for
both patient groups," and it held true for patients of heart
transplant centers as well as community medical practices.
in the AlereNet daily monitoring system group relied on a technology
system that included an electronic scale and personalized response
mechanism tied into their home telephone line. They were instructed
to weigh themselves and to answer a set of five questions tailored
to their individual symptoms twice each day. The information
was sent to a control center and reviewed by nurses once daily
over the course of the study.
in the standard care group were advised to weigh themselves
daily and keep a log of weight gains and losses, and they were
instructed to contact their personal physician about weight
increases above a prescribed amount or about any worsening
symptoms. They were also asked to bring their weight log with
them to the study's regularly scheduled cardiologist visits.
"We are not
certain what caused the disparity in mortality rates," Dr.
Goldberg said. "But the sole difference in the two groups appears
to be the daily monitoring by trained nurses in the AlereNet
group, which means those patients may have been more likely
to benefit from rapid medical intervention."