Many centuries ago, there were all kinds of explanations as to what caused disease in humans. Maybe your humours were out of kilter, maybe you were possessed by demons - or worse still, by the devil himself!
The germ theory of disease really only emerged in the late 19th century. And the idea of an antibiotic, which might fight these germs, began to take hold.
The actual word "antibiotic" dates back to 1889, when a pupil of Louis Pasteur, called Paul Villeman, described the process where "life could be used to destroy life".
But in the timeline of antibiotics, the name Alexander Fleming stands out, when he observed in 1928 that colonies of the bacterium Staphy-lococcus aureus could be destroyed by the mold Penicillium notatum. And so, the first truly effective antibiotic came into widespread use...
To many people, this antibiotic, penicillin, was a miracle drug, and it spawned decades of research into antibiotics, giving us hugely (and some would say "artificially") elongated life-spans.
But in more recent years, many argue that the miracle is wearing thin. Antibiotics are so widespread these days, that we are developing resistance, the effects of these sophisticated antibiotics are wearing off. They're also passing through our bodies, and entering the environment, with unpredictable consequences for wildlife and nature.
Barry McMahon is a lecturer in Wildlife Conservation at UCD. He's been taking a look into this phenomenon, and he joins us in studio to let us know what he's uncovered...