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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