Building Numbers
The earth is 4.5 billion years old.
A simple number -- a span of time -- incomprehensible to humans as a reality, it may be conceived only as a symbol -- a wisp of human imagination. In our apprehension, this number carries the empty weight of a prefix like giga or tera, a technical meaning, of little import or meaning to everyday life. Zeroes, meaning an impossible nothing, gather to mean an inconceivably more as they accumulate.
Forged by forces unknowable, solidified and silent for billions of years, this planet undistinguished from a billion other planets, also drifted lifelessly through an infinite lifelessness.
After a few hundred million years, prokaryotes (and others) decided to become.
Why they decided to become, I cannot say. I think the universe demands it, but Newton -- and many others -- might scoff at such heresy.
Anyway, they became. And became. And became...
Here's an old riddle:
How many prokaryotes then? Who knows? Who can count that many? And who cares about unicellular creatures anyway?
I suppose you have to subtract the dead ones. So okay, one inconceivably big number and another inconceivably big number -- but when the second number is less than the first, that is life!
When the second number is larger than the first, that is death.
When the second number is bigger than the first for a sustained period, then extinction ensues.
Around the 2.1 billionth year (give or take), something happened.
Of course this sucks for those anaerobic critters who suffocated in inconceivably huge numbers. (Good thing for them they were single-celled creatures. They can stave off extinction because the smaller the creature, the more capably it evolves. Also they can retreat to the very fringes of a chemically diverse planet, even one becoming less diverse, inhabiting the small inhospitable spaces.)
So what happens when the chemistry of the planet changes radically?
Mass extinction.
But who -- in reality -- counts such inconceivably large numbers of lost individuals and extinct species, especially when there are trillions upon trillions of dollars, euros, yuans, pesos, rupees, etc to be shoveled into a bank account?
After a few hundred million years, prokaryotes (and others) decided to become.
Why they decided to become, I cannot say. I think the universe demands it, but Newton -- and many others -- might scoff at such heresy.
Anyway, they became. And became. And became...
Here's an old riddle:
If a chessboard were to have wheat placed upon each square such that one grain were placed on the first square, two on the second, four on the third, and so on (doubling the number of grains on each subsequent square), how many grains of wheat would be on the chessboard at the finish? (Ans: The total number of grains equals 18,446,744,073,709,551,615)[source]Assume, (an extreme improbability), one single prokaryote cell in the very beginning. The next day, that single cell becomes two, the day after, four ... and so on for 64 days. Now continue this for a year ... ten years ... a million years ... two billion years!
How many prokaryotes then? Who knows? Who can count that many? And who cares about unicellular creatures anyway?
I suppose you have to subtract the dead ones. So okay, one inconceivably big number and another inconceivably big number -- but when the second number is less than the first, that is life!
When the second number is larger than the first, that is death.
When the second number is bigger than the first for a sustained period, then extinction ensues.
Around the 2.1 billionth year (give or take), something happened.
The Great Oxygenation Event (GOE), also called the Oxygen Catastrophe or Oxygen Crisis or Great Oxidation, was the biologically induced appearance of free oxygen (O2) in Earth's atmosphere. This major environmental change happened around 2.4 billion years ago...
First, it oxidized atmospheric methane (a strong greenhouse gas) to carbon dioxide (a weaker one) and water, triggering the Huronian glaciation. The latter may have been a full-blown, and possibly the longest ever, snowball Earth episode, lasting 300-400 million years.[6][7] Second, the increased oxygen levels provided a new opportunity for biological diversification, as well as tremendous changes in the nature of chemical interactions between rocks, sand, clay, and other geological substrates and the Earth's air, oceans, and other surface waters. Despite natural recycling of organic matter, life had remained energetically limited until the widespread availability of oxygen. This breakthrough in metabolic evolution greatly increased the free energy supply to living organisms, having a truly global environmental impact; mitochondria evolved after the GOE. [source]Imagine! Lots of little critters get together, given sufficient food and sufficient time, change the chemistry of the entire planet!
Of course this sucks for those anaerobic critters who suffocated in inconceivably huge numbers. (Good thing for them they were single-celled creatures. They can stave off extinction because the smaller the creature, the more capably it evolves. Also they can retreat to the very fringes of a chemically diverse planet, even one becoming less diverse, inhabiting the small inhospitable spaces.)
So what happens when the chemistry of the planet changes radically?
Mass extinction.
An extinction event (also known as: mass extinction; extinction-level event (ELE), or biotic crisis) is a sharp decrease in the diversity and abundance of macroscopic life. They occur when the rate of extinction increases with respect to the rate of speciation. Because the majority of diversity and biomass on Earth is microbial, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the biosphere rather than the total diversity and abundance of life. [source]This is how to build death, countless species at once.
Is the biosphere today on the verge of anything like the mass extinctions of the geological past? Could some equivalent of meteorite impacts or dramatic climate change be underway, as humankind's rapid destruction of natural habitats forces animals and plants out of existence?This is what happens when a single species succeeds so dramatically. It builds its own death ... along with death of billions of other multicellular species that cannot adapt to such extreme environmental changes.
Increasingly, researchers are doing the numbers, and saying, yes, if present trends continue, a mass extinction is very likely underway. The evidence is pieced together from details drawn from all over the world, but it adds up to a disturbing picture. This time, unlike the past, it's not a chance asteroid collision, nor a chain of climatic circumstances alone that's at fault. Instead, it is chiefly the activities of an ever-growing human population, in concert with long-term environmental change.[source]
But who -- in reality -- counts such inconceivably large numbers of lost individuals and extinct species, especially when there are trillions upon trillions of dollars, euros, yuans, pesos, rupees, etc to be shoveled into a bank account?
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