In nature, all organisms compete with each other for resources in order to survive. Competition between members of the same species is what makes organisms evolve.
This theory of competition and ‘survival of the fittest’ is called Natural Selection, and was originally proposed by Charles Darwin in his book “On the Origin of Species” in 1859. Darwin observed that within a species, different individuals show wide degrees of variation. He proposed that individuals with characteristics most suited to their environment are more likely to survive, reproduce, and pass on these characteristics. Meanwhile, individuals that are less well adapted to their environment might not survive and reproduce. Their less well adapted characteristics will eventually become removed from the population.
This process causes species to change gradually, and enables new species to eventually emerge. After it was published, “On the Origin of Species” caused a storm of controversy and Charles Darwin was ridiculed, but his theory of natural selection is now widely accepted. During the twentieth century we discovered that the characteristics of an organism that are passed from one generation to the next are controlled by genes.
Scientists were then able to explain Darwin’s theory of natural selection in terms of the selection of favourable genes. Natural selection can directly impact humans when it comes to treating disease. Discovery of the antibiotic penicillin in 1928 was lauded as a great advance in therapeutic medicine, and it soon became widely used. However, within just a few years some bacteria could withstand the effects of penicillin – they had adapted a resistance to the antibiotic.
These “fitter” bacteria survived, and in the late 20th century bacterial populations began to emerge that were resistant to penicillin. Nowadays, antibiotics are used more sparingly and scientists are attempting to find other ways to treat infections.
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