At first glance, these are just rocks. They look a bit like giant mushrooms or balls, but in general nothing unusual - stones are like stones. And they are alive. These are the most ancient inhabitants of our planet.
However, it is not a fact that you will be lucky enough to contemplate them. “Living stones” are found only where there are no people willing to eat them, and there are very few such places. One of them, for example, is located in the salty shallow waters of the Atlantic coast of the Bahamas, the other - off the coast of Western Australia in the so-called Shark Bay (Shark Bay).
“Stones” need to breathe and receive the sun's rays, so they can “grow” only in shallow water zones: completely salty, or, on the contrary, desalinated. And also where salt streams are periodically replaced by fresh ones and for some reason do not have external "predators" that would not feed on "stones". At the same time, the remains of such, but much more ancient organisms are found all over the world. We are talking about colonies of cyanobacteria, or blue-green algae - large bacteria capable of photosynthesis, with the complex name "stromatolites", although this term is often used to refer to the ancient fossils of these organisms.
Translated from Greek, the word "stromatolite" means something like "stone litter". So it is: stromatolites, or microbial mats, are mountains of living bacteria that use carbonate, calcareous, dolomite, less often phosphate, silica and ferruginous deposits of rock that accumulate in the ocean as a result of sediment of various dissolved in water substances.
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From it, stromatolites form their "apartment building", somewhat reminiscent of an anthill, simply structuring the sedimentary rock for themselves: all unnecessary is cut off, and the necessary floors are completed by gradual accumulation of sediment and all the same bacteria. The mat consists of a huge number of such "floors" - layers of sedimentary rock, between which there are so-called filamentous bacteria that can move - mostly up and down such a structure. In this case, the movement speed is about 2 cm / h.
Cyanobacteria, photo fragment.
Why would they move at all? To catch the sun's rays above, where stromatolite peeps out of the water, and below, in shallow water, life-giving moisture. However, a cyanobacterial mat consists of different types of microorganisms: some of them, for example, cannot tolerate air and carry out their work to maintain the life of the colony inside the "stone", someone is building new "floors". The latter is not a fast process: the growth rate in height in modern stromatolites is approximately only 0.3 mm per year.
What is the purpose of life for such an organism? Continue your race, and also release oxygen. The ancient stromatolites did the same. They, together with phytoplankton, filled our atmosphere with life-giving oxygen. After all, the oldest remains of cyanobacterial mats were found in the Isua Formation in Greenland (they were described in 2016 by scientists from universities in Australia and the UK). Their age is 3.7 billion years.
In that hoary antiquity, our planet looked not like a hospitable blue ball, but like a black stone, dotted with bloody "boils" of volcanoes and traps. Volcanoes spewed out poisonous smoke and gas - there was no trace of oxygen, since there were no plants capable of emitting it. The role of the latter was played by the stromatolites, which reigned on the planet for millions of years. It is due to the absence of "predators" in those distant times, as well as the large number of shallow seas (there was little water on the planet then) and their remains are found all over the world.
In fact, stromatolites are the oldest form of life. From such a form or similar to it, all living things on the planet came, including all of us, therefore, with certain reservations, stromatolites can be called our most distant forefathers.
Olga Fadeeva