Seeing the risks of humanity’s hand in species evolution
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Humans are frighteningly efficient predators Bacteria, parasites evolve to evade antibiotics, drugs
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Human predation is causing target species to evolve to reproduce at younger ages and smaller sizes, to their short-term benefit but to the long-term harm of the species.
“Humans are frighteningly efficient predators,” said J. Stanley Cobb, a lobster expert who retired recently from the University of Rhode Island.
Mortality regime
“They impose mortality in specific ways, at particular stages of the life cycle. If we believe that natural selection has shaped the life history characteristics of a species, then we have to believe that a different mortality regime will affect life history.”
Because humans discovered fire, the benefits of hunting in teams and the bounties of agriculture, people have been changing the natural landscape, causing plants and animals to evolve in response.
Starting perhaps 12,000 years ago, when people in what is now the Middle East began turning wolves into dogs, humans have domesticated animal species as varied as cows to cats.
They initiated or encouraged changes that turned weedy grasses into crop plants like rice and corn. Stone Age hunters may even have helped drive some ancient creatures, like woolly mammoths, to extinction.
In a report in the journal Science, researchers led by Jeff Feder, a biologist at Notre Dame, say the introduction of apples to North America in the 17th century eventually led some fruit flies that had specialized on hawthorn fruit to branch out to apples instead.
By the mid-1800s, the scientists say, the two groups of flies had become genetically different. And that, in turn, encouraged modifications of parasitic wasps that feed on the flies. Human behaviour has affected human evolution as well.
Cattle-herding peoples developed an ability to digest milk as adults through mutations that provided a definite survival advantage when times were hard.
But those were low-technology days. Since the beginning of the Industrial Revolution, humanity’s collective ability to change the world has been powered by fossil fuels and multiplied by machines. Often, the result has been evolutionary change at a fast pace and on a broad scale.
Adapting to drugs
Researchers have long known that bacteria evolve to evade antibiotics, and that parasites, like those that cause malaria, adapt to drugs used against the disease.
More recently, researchers have reported that cod, overfished for decades off New England and the Canadian Maritime Provinces, have begun reproducing at younger ages and smaller sizes.
The shift improves the chances of reproducing before being killed.
But at least as far as the fish are concerned, the change is harmful in the long run, according to Paul Paquet, an environmental scientist at the University of Calgary. The spawn of younger fish do not seem to be as robust as the spawn of older fish.
As climate warms, plants in the Rocky Mountains are moving to higher elevations, where it is cooler. In some areas of New England, researchers report that trees, shrubs and flowers are in bloom a week or two earlier than they were even a century ago.
And the cast of characters seems to be changing in the tide pools of Monterey Bay, where plants and animals adapted to warmer water seem to be moving in. — New York Times News Service
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