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Why does antibiotic resistance happen?

Antibiotic resistance is a natural phenomenon. Resistant bacteria are found on and in humans, in our environment, on farms, and on animals. They are all around us because resistance happens naturally as bacteria defend themselves against attack. A paper published in Nature in 2011 found resistant bacteria in the frozen remains of a woolly mammoth, and demonstrated that the genes that confer resistance to antibiotics were present in bacteria 30,000 years ago. Gerald Wright, who led the study, said: “This isn’t surprising, since that type of bacteria is the source of many antibiotics. These bacteria  produce probably 80% of the drugs currently used today – they also make anti-cancer agents, they make immune suppressants, they are remarkable little chemists. Scientists don’t yet know why soil bacteria have a tendency to make antibiotics and be resistant to antibiotics, but they speculate it may help them compete with other bacteria in an environment crowded with millions of bacterial species.