katydids hit the highest notes
TRANSCRIPT
In brief–
3 times as much tryptophan as
their wild cousins (Journal of Archaeological Science, in press).
Kerem speculates that
prehistoric people knew
chickpeas were nutritious. “It
probably made them feel good,”
he says. Not everyone is convinced
that chickpeas kick-started
human empires. “There is no clear
indication of when selection for
increased brain effects occurred –
was it 10,000 years ago or 5000?”
says Bruce Smith of the
Smithsonian Institution in
Washington DC.
Wild chickpeas are rare and
difficult to cultivate, so there
must have been a good reason
why our ancestors persevered
with growing them around
11,000 years ago.
That reason, says Kerem, is
the amino acid tryptophan – a
precursor of the neurotransmitter
serotonin. Increased amounts in
the diet may improve
performance when under stress.
Tryptophan also promotes
ovulation, an advantage during a
time of human expansion.
Cultivated chickpeas had over
THE clouds of global warming
don’t exactly boast a silver lining,
but there is a little bonus. Melting
sea ice in the Arctic is enabling
ocean waters to soak up more
carbon dioxide from the
atmosphere. Ice retreat over the
last 30 years has tripled the
amount of CO2 the Arctic Ocean
can absorb.
Nick Bates of the Bermuda
Institute of Ocean Sciences
and colleagues calculated CO2
uptake in the Arctic Ocean from
measurements taken from the
Chuckchi Sea and Canada basin in
2002 and 2004. They found that
CO2 uptake from the atmosphere
increased dramatically during
the summer months, when sea
ice was at a minimum
(Geophysical Research Letters,
DOI: 10.1029/2006GL027028).
“Sea ice acts as a barrier to gas
exchange,” says Bates. Overall
they calculated that the entire
Arctic Ocean is currently able to
absorb up to 66 million tonnes of
CO2 per year. Future ice-melt may
increase absorption by a further
20 million tonnes per decade.
However, this won’t be enough to
offset global warming: currently
worldwide emissions amount to
over 30 billion tonnes per year.
Arctic melt soaks up carbon dioxide
NIGHT-TIME in a tropical rainforest,
and lonely male Arachnoscelis katydids make their presence known
with a burst of intense sound. You
won’t hear it, though, because they
produce the highest-frequency
ultrasound of any known insect.
Members of the cricket and
grasshopper family are famous for
their ability to sing, and most emit
chirps at frequencies humans can
hear. Some katydids produce
ultrasonic chirps by rubbing their
forewings together, pushing a
scraper on one wing across a series of
pegs on the other. This won’t do for
Arachnoscelis species, though.
Fernando Montealegre-Z and Glenn
Morris from the University of Toronto
in Canada discovered that they chirp
at 130 kilohertz, which is too high a
frequency to be generated by merely
rubbing the wings together.
The researchers collected the
katydids from the Colombian
rainforest, and as well as measuring
their chirps they looked at their
wings with an electron microscope.
This revealed that as the wings rub
against each other, the scraper
wedges itself behind one of the pegs
and distorts. When released, it springs
back into shape, emitting a pulse of
ultrasound (Journal of Experimental Biology, vol 209, p 4923).
“By using elastic energy, the
animal saves metabolic energy, as
the muscles do not contract at an
almost impossible speed,” says
Montealegre-Z.
THEY have already been branded
gas-guzzling road hogs. Now the
reputations of sports utility vehicle
owners may be further sullied with
the finding that they are more likely
to be unsafe drivers.
SUVs are four-wheel-drive cars
built on top of a tall, van-sized
chassis. Their supporters have argued
that the high vantage point enables
them to see further and makes them
safer drivers. To test this, Jared
Thomas and Darren Walton of the
Opus behavioural sciences lab in
Wellington, New Zealand, watched
1196 SUV and car drivers on motorways
to see whether they drove with their
hands at the “ten-minutes-to-two”
position on the steering wheel – a
sign of a safe, alert driver.
They found that SUV drivers were
55 per cent more likely to drive with
only one hand on the top half of the
wheel than drivers of regular cars
(Transportation Research F, DOI:
10.1016/j.trf.2006.10.001). “Being in
larger, taller vehicles, SUV drivers
believe they are safer and possess a
lower level of perceived risk than car
drivers,” says Thomas.
Steve Dethick of DriveTech, a driver
training school in Crowthorne, UK,
believes that an SUV’s size is the main
problem. “It lulls drivers into a false
sense of security that they will survive
an impact,” he says.
COULD the humble chickpea have
changed the course of history?
As one of the founder crops
cultivated in the fertile crescent
of Mesopotamia, the chickpea’s
nutritional benefits have been
cited as one of the reasons for the
rise of civilisation there.
Now Zohar Kerem from the
Hebrew University of Jerusalem,
Israel, thinks he has evidence to
support that view. Kerem and
colleagues collected wild
chickpeas (Cicer reticulatum) and
compared their nutritional value
with that of cultivated varieties.
DITA
KLI
MAS
DAVI
D HO
FFM
AN/A
LAM
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‘Brainy’ chickpeas conquered the world
16 | NewScientist | 6 January 2007 www.newscientist.com
SUV owners need a hand to drive better
Katydids hit the highest notes
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