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Randolph E. Schmid
The Associated Press
The impact of technology has increased so much in recent years that
``humans may be world's dominant evolutionary force,'' said Harvard biologist Stephen
R. Palumbi.
He writes in Friday's issue of the journal Science that the cost to
society
of drug-resistant bacteria, pests that can survive DDT and other poisons and
superweeds could be more than $50 billion a year in the United States alone.
Many of the ideas in Palumbi's paper have been discussed previously. But he
brings them all together in this report, commented Michael Bell, who teaches
ecology and evolution at the State University of New York at Stony Brook.
``The literature is full of examples of rapid evolution and when you look at
the cases, human intervention is almost always involved,'' Bell said. ``He
(Palumbi) was clever enough to see that there is a common theme here and he
has provided a list of tools that can be used to mitigate the problem.''
Palumbi noted in a telephone interview that humans have been applying the
principles of evolution for thousands of years by selectively breeding
livestock and saving and replanting the best crops.
``It used to be we were only affecting our own farmyards, now we are
affecting the whole planet,'' he said.
Indeed, it is human activity that dominates the availability of fresh water
and usable land, fisheries production, the amount of carbon dioxide in the
atmosphere and environmental changes worldwide, he wrote.
Illustrating how quickly evolution can have an effect, Palumbi pointed out
that, only a decade after the 1939 discovery that DDT killed insects,
resistance to the chemical was reported in house flies.
Likewise, diseases such as AIDS, tuberculosis and others have increasingly
evolved to become resistant to drugs.
And more and more farmers are forced to increase their doses and types of
pesticides as insects and weeds evolve to resist them, Palumbi added.
Other changes he cited include increases in dwarf male salmon, which now
return from the sea early to increase their survival, and the slowing of
growth rates among fish under heavy fishing pressure.
The direct costs of treating drug-resistant diseases and of damage to
agriculture total between $33 billion and $50 billion annually, he
estimated.
``They are direct, out-of-pocket expenses and are certainly
underestimates,''
he said in a telephone interview.
Among the costs he included in the total are $1.2 billion for respraying
fields because of resistant pests, $2 billion to $7 billion for loss of
crops
due to resistant insects, a similar cost for treating drug-resistant
diseases, millions of dollars for the development of new pesticides and
drugs
and other costs.
However, while human-driven evolution has become costly and in some ways
hazardous, ``once you understand a process, you can begin to control it,''
he
said.
Scientists can find ways to engineer the evolutionary process to ``slow the
arms race'' with pests and germs, Palumbi said. For example AIDS is treated
with a multi-drug ``cocktail'' in the hope of preventing resistance to a
single drug; pesticides are sometimes used in an overkill process called
pyramiding, and in other cases the most powerful
drugs are withheld until all else has failed to prevent germs becoming
resistant.
Other strategies could include:
-Cycling through different herbicides rather than using the same one
repeatedly.
-Screening for sensitivity before treatment to allow use of a narrow range
of
drugs.
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