Evolution is the process through which more complex systems arise from less complex ones. Evolution is evident everywhere, but is not self-evident. Why would complexity arise from simplicity, instead of the more “natural” path of devolution and disorder? How galaxies have formed from the soup of particles, since the big-bang? Why on Earth, life has evolved from simple single-cells to complex human beings?
Uniform and random systems are not conducive to evolution. Minor instabilities during the big-bang are thought to have caused the initial gravitational seeds, around which, galaxies grew 14 billion years ago. Similarly, environmental instabilities have favored increasing complexity and biodiversity on Earth, since life started 4 billion years ago. So in a sense, order has emerged from chaos through instability, because that chaos carried the seeds of order from the very beginning.
The “immortal” single-celled creature could theoretically duplicate its “selfish” genes forever, producing two identical daughters from each single mother. Each daughter would be of almost exactly the same character and genes as the mother. Therefore notionally, the single-cells could have competed with one another, through duplication and growth, until one of them would have dominated the entire planet Earth with its “selfish” gene. However, that same immortal quality of a unicellular, to duplicate without limitation, impaired its ability to endure a sudden and significant change of environment. Moreover, as the unicellular populations grew, that change in environment could actually arise from the life activities of the microorganism itself, as its internal “order” generated a multitude of external disorders.
Nevertheless, Earth is a constantly dynamic system; e.g. there is a continuous bombarded by the cosmic radiation that can induce genetic mutations in single-celled organisms. Therefore, the copy-and-paste of DNA has never been exactly accurate! Mutations could “give birth” to new genes and to new cell characteristics, which would pass from mothers to daughters and survive, if they could enhance their chances of survival. Over the billions of years, even the “immortal” unicellular microorganisms have always been subject to change and evolution; resulting in new variations, races and species.
Four billion years ago, when the first lifeforms emerged on Earth, the atmosphere was drastically different from today. There was much more CO2 and almost no oxygen! The first cells thrived on getting their energy from thermal or chemical sources, and used that energy to build their cellular building blocks (genes, proteins and carbohydrates). That early “paradise” lasted for a billion years, unit it was dramatically altered with the emergence of photosynthesis.
Photosynthesis is the biochemical process that captures the sun’s radiative energy by combing CO2 and water to make carbohydrates, while releasing oxygen as a by-product. Starting 3 billion years ago, with ample sunshine and atmospheric CO2, the microorganism Cyanobacteria mutated to produce sugars through photosynthesis, which made her extremely successful and prolific. The success of photosynthesis eventually released some 1,000 trillion tons of oxygen into the Earth’s atmosphere!
Oxygen is today considered as the essence of life for all animals which cannot last without breathing every minute of the day. However, from a strictly biochemical point of view, oxygen is a potent biocide (killer of living things). You can use oxygen to kill (oxidize) most organic matter, and that is exactly what happened 2.5 billion years ago to almost all the original microorganisms, when the photosynthesis unleashed by Cyanobacteria dramatically increased the oxygen concentration in Earth’s atmosphere.
That oxygen-induced mass extinction is recorded in Earth’s geology as the Great Oxygen Holocaust. Nearly all the “immortal” microorganisms that were obligate-anaerobes died and disappeared. CO2 concentration in the atmosphere dropped and the emergent oxygen in atmosphere reacted with pre-existing methane (a potent greenhouse gas) and dropped its concentration to near zero. The result was a disastrous period of cold temperatures that created the worst ice ages ever (Snowball Earth)!
The fact that proliferation of tiny single-celled microorganisms, driven by their “selfish” genes, could impact the entire Earth surface and atmosphere, clearly indicates that around 3 billion years ago a new “unit” of evolution had emerged on our planet. We can call that new unit the “ecosystem” and its playing ground has been the biosphere. It does not mean that the selfish genes stopped working on the evolution of microorganisms; just that a new higher-order (ecosystem) had emerged which comprised of a multitude of the lower-orders (microbes).
Eventually aerobic microbes, which could consume oxygen, evolved and established equilibrium versus the CO2 consuming photosynthesis. Free oxygen has been an important constituent of the Earth’s atmosphere, ever since. Due to that vital check-and-balance and many more like that, the story of ecosystem’s evolution has dominated the past 2 billion years of Earth’s biosphere; carrying within it the equally-important subplots of genetic evolution that continuously play underneath all the big and small environmental changes.
The story of evolution of ecosystems is not a single-hero saga, but a multi-generational and multi-player grand plot that depends on biological competitions as well as cooperative inter-species links. Those links have fostered biodiversity on Earth, rather than creating a single-species situation. In a biodiverse ecosystem, the waste (disorder) generated by one organism can be nourishment for another, and vice versa. Disorder and waste, which unchecked can kill any single organism, are minimized and harnessed to result in a nearly maximized utilization of energy and resources - constantly in reuse, recycle and regeneration.
Looking at a galaxy like our own Milky Way, a similar sort of “ecosystem” formation and diversity is evident among the dust clouds, stars and the lonely central black-hole. As though evolution (emergence of order from chaos) has been playing similar musical tunes through a variety of instruments, and throughout an astonishingly wide range of sizes and scales!
Billions of years ago, the emergent bio-diversified ecosystems evolved to behave like super-intelligent creatures, although they were literally made of a multitude of seemingly unintelligent unicellular microbes. Under greater scrutiny, each of those microbes on its own-right was also a highly intelligent biological supercomputer. Furthermore, under an electron-microscope, each of those single-cells contained thousands of knowledgeable and evolving genes.
The bio-diversified multitudes of ecosystem have proven to be robust “units” of evolution, which have endured many more climate changes, asteroid impacts and holocausts. It is only very recently that the underlying evolution of genes and species has resulted in a “superman” who is busy creating his own ecosystems. This “intentional” global tampering with the biosphere has created a new extinction event (holocaust) that is carrying Earth into uncharted trajectories.
Picture: Stromatolites from extinct species after the Great Oxygen Holocaust.
Reference: Evolutionary Instability, by Gebhard Geiger, Springer 1990.