In Zoology, we often discuss organisms as being in two broad categories: specialists, and generalists. The concept behind these two categories is that evolution by natural selection can favor both strategies for a species, as they both have benefits and consequences.
Specialist species evolve to be almost perfect for their niche. You can think of animals which inhabit a very particular habitat, like pearl fish, or an animal with outstanding camouflage. Specialists are hard to out-compete in their niche, because they are so damned good at inhabiting it. However, if their environment changes, even slightly, they can suffer the consequences of no longer being so well adapted at their new environment, and becoming so specialized also brings with it more rigidity in your ability to evolve to adapt to changing circumstances. A drastic environmental change can wipe out a specialist species, as they cannot evolve quickly enough to adapt and ensure their own survival.
Generalists, on the other hand, are able to live in a much wider range of environments, but being able to do so also means that your species cannot be perfectly adapted to each one. A generalist will most likely be out-competed by a specialist in one particular habitat, but it compensates by being able to inhabit other niches outside of the specialist’s reach, and also by being more flexible in dealing with environmental changes. Humans are a prime example of a generalist species, having been able to figure out a way to thrive from Siberia to the Sahara. When speaking of generalists, only microbes are putting us to shame. They can inhabit deep sea vents, inside glaciers, and can even survive in space. Now, it seems that they keep putting Homo sapiens to shame, by having taken up the art of sculpting cities.
Just recently, divers exploring the shallow seafloor off the coast of the Greek island of Zakynthos thought they had come across a real-life version of a long-lost city when some very unusual underwater formations came into view, including some strange pillars, walkways and even what appeared to be courtyards. Writing in the journal Marine and Petroleum Geology, a team of environmental researchers have now revealed that these peculiar structures are not actually archaeological remains at all.
Had some unforetold disaster wiped out the unfortunate residents of a previously undiscovered and undocumented civilization? Had all the people living there escaped before the catastrophe hit, taking all their precious ceramic goods with them? Unfortunately for archaeologists, geochemical dating techniques revealed that these strange seabed features dated back to the beginning of the Pliocene era – about 5 million years ago – long before the genus to which humans belong to, Homo, walked the Earth.
After being carefully examined by archaeologists, geologists and professional divers from both Greece and the United Kingdom, it was clear that the disk and doughnut-shaped columnar features were a type of mineralization feature. They were being generated by the escape of chemicals, mainly methane, emerging from hydrocarbon-rich layers hiding below a semi-ruptured fault.
Microbes lurking in the sediment there appeared to be using the carbon in the methane as a source of energy. As they oxidized the methane, these bacteria and archaea were inadvertently changing the chemistry of the sediment they were living in to form a natural cement. To geologists, this is known as “concretion,” and it can result in a number of new rock formations.
It was the bacteria, folks, and they’ve been doing it well before humans even existed, let alone came up with such a concept.
Of course, it is a little unfair to compare humans and bacteria when it comes to who-is-the-greater-generalist. After all, Homo sapiens is one species, where as bacteria and archaea have countless species to their name. Of course, there is also the fact that microbes also colonized us, to the point that the microbial genes that we carry around with us outnumber our own genes by over 10:1, making us, in a way, more microbe than human.
OK, maybe they win after all.