The talent that gave
humans alone mastery over language may have been identified. In a new study,
psychologists Marc Hauser of Harvard University and W. Tecumseh Fitch of the
University of St. Andrews, Scotland, compared the ability of monkeys and humans
to recognize grammar rules.
The concept of word ordering the idea
that certain kinds of words must follow other types of words, as in the
article-pair "a tree" is a basic component of language. The scientists
played recordings of one-syllable words spoken alternately by a man and a woman
to both cotton-top tamarin monkeys and college
students. The monkeys looked at the loudspeaker whenever the pattern varied,
indicating they had noticed the change; the human subjects also picked up the
pattern alterations. The scientists then played recordings of a man speaking one
to three words, followed by a woman speaking the same number of words. The rule
corresponds to the "if ... then ..." phrase structure of language.
All
the human subjects correctly identified pattern changes, even though they were
often unable to articulate the structure of the pattern itself. The monkeys,
however, recognized none of the variations. The cognitive ability to spot
recursive language patterns may have been what allowed humans to develop their
linguistic genius, the researchers report in the journal
Science.
Mountain Lions Lurk
Nearby
Many hikers set out in
search of quiet and solitude, but if you're hiking in San Diego County, chances
are you're not alone. A new study suggests mountain lions linger unsettlingly
close to human recreational trails.
Walter Boyce of the University of
California, Davis Wildlife Health Center and colleagues tracked the movements of
20 radio-collared mountain lions living in and around Cuyamaca Rancho State Park east of San Diego. They found the
big cats often hid in brush a mere 100 to 300 meters from trails and might move
even closer in the late afternoon. The animals spent most of the night hunting
and occasionally ranged into nearby communities to kill livestock or pets.
Usually, however, they stuck to wild game such as deer and bighorn
sheep.
The study ended December 31, just days before a mountain lion
killed one mountain biker and injured another in Orange County, south of Los
Angeles. Expanding human communities and a hunting ban has made human encounters
with the big cats more frequent in recent years. Yet puma attacks in California
are very rare. Only a dozen attacks have been recorded since 1890; of those,
five ended in deaths.
Humans Gained Color
Vision, Lost Smell
Our ability to appreciate
the colors of the rainbow came at the expense of our sense of smell. The
advantages of full-color vision, scientists say, rendered a sensitive nose
unimportant. Evolutionary biologists Yoav Gilad and Svante Paabo of the Max Planck Institute for Evolutionary Biology
in Leipzig, Germany, analyzed olfactory genes in humans and 18 other
primates.
Of this group, humans have the weakest olfactory abilities.
About 60 percent of the human genes studied carry a mutation that renders them
inactive. Old World monkeys and apes have lost 30 percent of these genes. By
comparison, less than 20 percent of the New World monkey genes are
inactive a figure similar to that in dogs with one exception.
Howler monkeys, like their Old World cousins, had lost 30 percent of these
genes. And like humans, howlers have full-color vision.
These smell loss
levels are no coincidence, the researchers report in the Public Library of
Science. The ability to see rotting or diseased food may have made the need to
smell signs of poisons or decay evolutionarily less important, allowing animals
with Technicolor sight to jettison their smelling genes with few consequences to
survival.
Disgust Helps Humans Dodge
Disease
Disgust may have evolved
to help humans avoid disease and illness. People find objects that might be
contaminated with bodily excretions or fluids far more disgusting than other
images, report scientists in the journal Royal Society Biology
Letters.
Valerie Curtis of the London School of Hygiene and Tropical
Medicine and colleagues showed 40,000 test subjects a series of images and asked
them to rate how disgusting each picture appeared. The images included photos of
a white cloth stained with either a blue or brownish-yellow liquid, and a
viscous liquid that was either blue or yellow with red flecks. The subjects
consistently rated the images that appeared to be associated with disease,
feces, or blood as far more disgusting than the more neutral blue
images.
Women and children had the strongest sense of revulsion, while
adult men were less discriminating. Older people also seemed to be less
squeamish. Women's sense of disgust increased during their childbearing years
and declined with age. The scientists conclude that disgust may be stronger in
women because they are the primary caregivers for children.
Ground dwellers such as
gophers and moles face a tricky conundrum: how to find their way around in
complete darkness. Now scientists have discovered how one subterranean resident,
the naked mole rat of Africa, can get around without GPS; it uses an internal
compass. Naked mole rats live in large colonies and seldom venture above ground.
They use their sense of balance and smell to navigate during short trips. Yet
these blind rodents embark on relatively long foraging trips.
To
determine how mole rats get around, Tali Kimchi of Tel Aviv University and colleagues placed mole
rats into laboratory mazes and let them learn how to find their way back to
their nests. But when the researchers began varying the magnetic fields
surrounding the maze, the mole rats got hopelessly lost.
The rodents stop
periodically to take magnetic readings and readjust their course, the scientists
report in the Proceedings of the National Academy of Sciences. Mole rats and wood rats are the
only land mammals known to have magnetic sensing ability.
Related
Links
Monkeys Illuminate Language
Advance: Scientific American / New Scientist / MSNBC (Science)
Mountain Lions
Lurk Nearby: San Francisco Chronicle (Associated
Press)
Humans Gained Color Vision, Lost Smell:
New York Times
Disgust
Helps Humans Dodge Disease: Discovery.com / BBC
Mole with Magnetism: Scientific American / New Scientist
http://www.enn.com/news/2004-01-28/s_12467.asp