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Humans
a Major Evolutionary Force
Excerpt by Randolph
E. Schmid, Associated Press
WASHINGTON
(AP) - No longer just the product of evolution, humans have become
one of the planet's major forces driving it.
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:
-Integrated
pest management, which reduces reliance on chemicals, thereby
lessening the chance of resistance.
-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.
On
the Net:
Science:
http://www.eurekalert.org.
Reference
Source 102
For
more information on how to prevent other diseases, use
PreventDisease.com's "Quick
Prevention Resources".
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