These genetic events occurred over millions of years of evolution and were undoubtedly rare, perhaps occurring only once in evolution. The success of these genetic changes also depended on subsequent selective pressures and genetic fine-tuning by mutation and other genetic mechanisms. Nevertheless, the molecular fossil record in the DNA of contemporary pathogens leads to the inevitable conclusion that microbial evolution is still dynamic and that these periodic genetic upheavals in microbes affecting their pathogenicity can occur at any time. To underestimate the evolutionary potential of microorganisms and their ability to survive, even in the face of enormous pressures to eradicate them and their effects on humankind, would be a mistake. Stanley Falkow and Lucy Tompkins, of Stanford University Infectious agents will emerge so long as there are microorganisms.
Humans help the evolutionary process sometimes unwittingly and sometimes by arrogance or ignorance.
Antibiotic resistance on a global scale in what seems such a short time comes as no surprise. Yet, application of a selective pressure on the microbes of the planet with antibiotics, a pressure that dwarfs the use of DDT in its scope, as well in the number of species that are affected, still remains a subject of debate after 50 years. As Pasteur said, the microbe will endure. Perhaps the fate of the last human is to be consumed by its own microorganisms. The record of horizontal gene transfer in Salmonella .