About 4.5B years ago, it seemed that a giant mass of gases formed into a cloud and coalesced into a planet we call Earth, and shortly thereafter the seas seemingly formed on its surface, and shortly after that the first forms of single-celled life (prokaryotes) emerged in the oceanic soup. That emergence seems to have been an accident, one of nature’s endless experiments with variety that somehow sustained itself. An electric spark, for no reason, with surprise consequences.
It was another two billion years before another apparent accident — the engulfing of an aerobic bacterium by an anaerobic bacterium — generated an explosion in the quantity of available energy to the symbiotic pair, sufficient to enable the creation of multi-cellular life (eukaryotes).
Nick Paumgarten in The New Yorker explains what happened next:
According to what is known as the endosymbiotic theory of biological complexity, [the unexpected emergence of mitochondria] is the reason we exist. That [engulfed] aerobic bacterium evolved into what we call mitochondria, the organelles that fuel all living creatures: the powerhouses of the cell. Each of us has hundreds of trillions of mitochondria. They convert glucose and oxygen into adenosine triphosphate, or ATP, the primary cellular fuel. They also help produce the essential hormones—among them estrogen, testosterone, and cortisol—and regulate cellular proliferation and death.
It’s not inconceivable that the rest of the body (brain, hands, heart, lungs, digestive tract) is merely an elaborate and sometimes clumsy apparatus for the nourishment of the mitochondria—that it is the mitochondria, and not Homo sapiens, who rule and foul the earth. Our cardiovascular system, that fantastic and vulnerable machine, is essentially a delivery system for the oxygen they require. The mitochondrion is the creature and we are merely its husk, its fleshy chrysalis. A newborn’s first breath? That’s the mitochondria, calling the shots.
This energy revolution was so extraordinary that it empowered, over the next two billion years, the creation of a vast proliferation of new self-replicating containers for these mitochondria, called ‘organisms’, using this energy to self-propagate, transport, and protect themselves. The containers are what we call plants and animals (including the human variety), and the transporting mechanisms evolved from flagella to roots to fins and feet and wings.
And then there was another energy revolution. One of the new mitochondria containers, called a ‘human’, evolved the capacity to use tools and extract energy from the earth, to create yet another layer of containers to protect itself and hence the mitochondria it hosts, containers called ‘buildings’, and yet another layer of containers to transport itself and hence the mitochondria it hosts, called ‘vehicles’. The buildings, vehicles and other products of the human containers were collectively called ‘artifacts’.
So now these mighty mitochondria, veritable miniature energizer bunnies, were running a staggeringly complex multi-layered empire: They’d evolved organisms to protect and transport themselves in ‘packs’ of hundreds of trillions, and some of those organisms had in turn evolved artifacts to protect and transport billions of organisms.
But something went wrong along the way. Due to an accidentally-evolved error in the wiring of the feature detection system (called a ‘brain’) of the ‘human’ containers, these containers mistakenly came to believe that the human ‘self’, a construct of the brain, was in control of the organism. This delusion was propagated through another human tool called ‘language’, and soon all human containers were infected, and began behaving in erratic and dysfunctional ways, attacking and killing each other and other organisms, and fouling the planet, threatening the survival of all organisms.
But this aberration did not last long, and the massive extinction event it precipitated reduced the total number of mitochondria on Earth by over 97%. What followed was a long period of rapid and then gradual decomplexification, with other smaller extinction events, and most of the mitochondria that survived propagated in much simpler containers. There were a few surviving human containers, but they were not well-adapted to the post-extinction environment and finally became extinct about a million years later.
And then about twenty million years after that, an unprecedented series of cosmic storms, created by exploding supernovas, ionized the planet’s surface and atmosphere, creating a new primordial soup in a world filled with fire and lava and lightning, and by accident an entirely different type of powerhouse emerged in some simple bacterials cells that had just been awaiting their turn to explode with newly-infused energy. And the two billion year long reign of the mitochondria on Earth was over…
But of course, it’s only a story.