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Humans a Major Evolutionary Force
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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

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