GIANT snakes, more than three metres long and up to 30 centimetres in
diameter, roamed Australia less than 100 000 years ago. And their anatomy casts
new light on the evolution of their modern counterparts.
A recent paper in Nature by John Scanlon of University of New South
Wales and Michael Lee of the University of Queensland describes their study of
two species of fossil wonambi, a giant snake which only became extinct during
the Pleistocene era. The wonambi, evidence of which has been found across the
continent, may still have been around in Australia when the first humans
arrived. If so, the researchers say, it was presumably driven to extinction by
hunting, along with the other megafauna. Scanlon and Lee argue the giant snake
could even be the origin of the 鈥渞ainbow serpent鈥� legends.
But the most crucial finding of the researchers is that the wonambi is not
related to any species alive today. It is extremely primitive, they say, similar
to the snakes 鈥渨hich lived alongside the dinosaurs, over 70 million years ago鈥�.
In the rest of the world such snakes disappeared a very long time ago, but
somehow they survived in Australia.
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The skull and teeth of the wonambi link it to a group of extinct marine
goannas called mosasaurs. Lee and others published a paper last year showing
that the mosasaur skull seems to be an intermediate stage between the inflexible
structure of lizards and the famously flexible head and lower jaw of snakes,
which allows them to engulf large prey.
One popular theory of the evolution of snakes is that they arose from lizards
which lost their legs to become more efficient at burrowing into the ground.
This would suggest that the ancestors of all modern snakes were small burrowing
varieties of lizards. But Scanlon and Lee鈥檚 study provides evidence that
primitive snakes were either marine creatures or large forms that did not
burrow. Their paper suggests snakes lost their legs and developed elongated
bodies to facilitate swimming or moving through dense vegetation.
A RECENT study in the Newcastle area has found that nearly half the babies
are passive smokers. And to make matters worse, research in the US has found
that low-tar cigarettes are just as dangerous as the real thing.
The pilot study of 193 infants by the Hunter Centre for Health Advancement
found that almost half tested positive for a major breakdown product of
nicotine. There is no reason to believe the sample is atypical, says Justine
Daley of the centre. So the study shows that babies are very likely to be
exposed to cigarette smoke. And this is believed to increase the risk of health
problems including asthma and other respiratory illnesses.
Babies suffer more from cigarette smoke than parents realise, Daley says.
Keeping the infant鈥檚 room a non-smoking area is not enough. 鈥淸Parents] need to
ensure there is no smoking throughout the house.鈥� The centre is developing
education packages to encourage this course of action, but it may not be easy to
convince smokers to go to such lengths to keep their exhaust gases away from
babies.
Some aware parents may be smoking low-tar cigarettes to reduce the risk, but
an American study has found that smokers of low-tar cigarettes naturally
compensate by taking longer or deeper puffs to supply the level of nicotine
their addiction demands.
Mirjana Djordjevic and colleagues from the American Health Foundation
recently published the results of their study of 133 smokers of low-tar
cigarettes in the Journal of the American Cancer Institute. The changes
to their smoking behaviour meant the smokers of low-yield cigarettes took in
about twice as much tar and nicotine as estimated by the official government
tests. This means the low-tar brands actually provide about the normal dose of
nicotine to the smoker and anyone else living in the same house.
On the strength of this, the lobby group Action on Smoking and Health (ASH)
has asked the Australian Consumer and Competition Commission (ACCC), to
intervene. It wants the consumer watchdog to take action against tobacco
companies for misleading advertising. 鈥淵ou would [hope] that an organisation
that goes out of its way to stop price collusion among foam mattress
manufacturers could do something about an industry that kills 18 000 Australians
a year,鈥� says Ann Jones of ASH.