The first bacteria
Some scientists think that bacteria were the first living things on Earth. According to current scientific thinking, they either came from reducing organic chemicals in watery soups or were bound to crystalline clay surfaces about 3.5 billion years ago. From that point, they evolved into different forms and adapted to whatever environment came their way. They experienced lots of changes. Earth cooled, land masses and oceans formed, and algae produced oxygen. Bacteria continued adapting as they formed consortia of organisms that acted as if they were single entities. Over time, these consortia, according to the endosymbiont theory, developed into plants, animals, and eventually humans.5
Bacteria still control the Earth as we know it. They are in and on every environmental niche where water is liquid on Earth. They even inhabit humans. Some are disease-producing, but most are not. Some are even
needed for our existence. If all bacteria were suddenly to die, all other living creatures would also die. However, if all the plants and animals were to die, the bacteria would still survive and adapt to their new environment to start a new cycle. This is a humbling concept and is well worth remembering as we approach the short 300-year history of microbiology, and the even shorter 70-year history of cosmetic microbiology.