(continued) Chapter 3. Long Evolution: Life Emerging
Definition of “Third Option”: Any possibility that sees beyond the common narrow-minded tendency to polarize any issue or condition allowing of disagreement into binary opposites – often extreme opposites – which perceive only two possible positions on the point of issue or disagreement. Never are there only two options. “Third option” possibilities typically occur only in those minds which, being trained or predisposed to avoidance of closed mindsets, are ever open to the broader prospects of options 4, 5 and …n. “Always seek the third option” therefore is perennial good advice.
Option 3. Life may have been carried to earth on comets or meteorites, or rock fragments flung here from the impacts of space rocks on our sister planets. All three possibilities carry the condition that life originated elsewhere in the universe, or elsewhere in our own solar system, even if it also happened to originate independently here on earth.
Extraterrestrial origin(s) of life is a perfectly feasible hypothesis. Organic chemical compounds are commonly found in meteorite fragments and are spectroscopically deduced in the ice and sludge of which comets are made. Life-friendly water, frozen or wet, is abundant on many bodies in space. By one means or another life somehow appeared on earth, so who’s to say it may not have happened many other times in many other places across the wide universe, even if nobody was out there to record it in a cosmic Bible, Koran or Upanishad? Scientists tell us organic traces most certainly got recorded in many of the rock fragments dislodged by meteoroid strikes on other planets and flung into earth’s gravity well, and they are all over those signs of fresh water flowing on Mars because we know where there’s water there could be life. Yes, extraterrestrial origin of life is a credible possibility.
Option 4. Life may have originated in the deep ocean depths, around very hot vents carrying mineral-rich water up from the magma to exits through the ocean floor. We know many kinds of bacteria survive and thrive around such vents; using chemosynthesis they convert inorganic molecules such as toxic hydrogen sulfide into sugars they can eat, just as plants employ photosynthesis to ingest carbon dioxide and give off oxygen. Whole ecologies have been discovered around these vents, with more complex critters such as worms and various crustaceans constituting a sophisticated food chain. Deep-ocean vents thus present a plausible option for generation of life which could have happened even if life also originated in other ways in other places, such as the n options.
Life may have originated in different places on earth, in different ways, and perhaps many times. Extremophile bacteria have been found alive and well – and reproducing – in water near the boiling point, beneath glaciers hundreds to thousands of feet thick, and in mines more than a mile underground. In all these places – the ground, the water, the air and other life, in every last nook and cranny of the globe – tiny life subsists by “eating” things you wouldn’t think living things could live on but they do. Our planet’s whole surface, from a mile and more down to the outer reaches of the air above, is a writhing, squirming, surviving, reproducing maelstrom of living life that we sometimes correctly call “the biosphere.” Though it has some fragile aspects, life clearly it is very hardy and simple life seems hardier (read adaptable) than complex life. Moreover, science’s estimate that ninety-nine percent of all microbial species are yet to be discovered reminds us how very much we still don’t know about the many ways life may have begun.
The pace of discovery is greatly quickening as new scientific tools for collecting genetic data from bacteria in their natural environments have been developed in just the past decade. Faster and cheaper sequencing of organisms’ entire genomes are revealing the existence of hundreds of whole new phyla within a mind-boggling array of previously unknown living diversity. This includes slow growing bacteria so ultrasmall that – like the viruses – their bodies don’t have room for all the DNA they need to be alive and so they manage by scavenging the missing essential nutrients from their environment. Almost unbelievable, and yet it is so: micro-bacteria found in Colorado groundwater latch onto larger bacteria, parasitizing amino acids and other needed nutrients until they suck their host dry and it dies. Microbes found in the slime of a hospital sink drain survive by living inside amoebas.
It is hard to conceive these “half-living” forms in any way other than as odd waystations in that twilight realm where non-living minerals, still yet today, are evolving into life.
Beyond this short list, an internet query on “life origins” will put you in touch with a bewildering batch of options, facts, learned opinions and wild speculations. One of these offers back-door learning via an interesting article in which scientist Casey Luskin lists the top five problems with current origin-of-life theories. You can learn a lot about any idea by reading the railings of critics who dislike it. Biblical scholars have in fact long used this method to discover a great deal about the various early Christian sects by studying the writings and rants of contemporary Gnostics and other churchmen who competed with and often despised each other. As previously noted, there is nothing in science (or religion) about which scientists (and churchmen) do not argue, often vehemently while growing red in the face. But, here and there, the humility of a truly open mindset gleams through, as in the comments of Harvard chemist George Whitesides during his acceptance speech upon receiving the Priestley Medal, the highest award conferred by the American Chemical Society:
The origin of life problem…is one of the big ones in science. … Most chemists believe, as do I, that life emerged spontaneously from mixtures of molecules in the prebiotic Earth. How? I have no idea.
When did life first evolve on earth?
Our current educated best guess is about 3.5 billion years ago – a little more than ten billion years after the big bang. Recalling that the earth is about 4.5 billion years old, recent chipping away at very old rocks raises speculation that life might even have been underway as early as four billion years ago – virtually as soon as earth’s crust formed and cooled enough to hold some water. We won’t consider that older possibility just yet because so many scientists are all queued up to criticize the alleged finding and pontificate on why it couldn’t possibly be so – even though it actually could. Never forget, the true odds on being right or wrong are always 50/50.
So let’s begin the story of life on earth about 3.5 billion years ago (BYA) when the earth was a billion years old, more or less. In earth’s long history, a few time boundaries are convenient for understanding, perhaps even remembering, the story of evolving life. The first is the Precambrian-Cambrian boundary, some half a billion years ago – four billion years after the earth formed, three billion years after we think life began on it. Before that Cambrian boundary, life-years are measured in (B)illions; after it they’re measured in (M)illions. After a prolonged three-Billion-year pre-Cambrian gestation came the half-billion-year Cambrian-to-present era in which life evolution moved along a bit faster.
During those three billion Precambrian years, we surmise that the first self-organized life with its capacity to reproduce exponentially got underway, survived and thrived. For the first billion years and more, its kind spread themselves all over such land and oceans as then existed and endlessly shifted about on the earth’s surface. Those trillions upon trillions of generations of tiny living things – not plants, not animals – were the simple ancestors whose more complex descendants would eventually evolve into the first single-celled organisms, i.e., the ancestors of the bacteria that today live in our guts and enable us to stay alive by causing the nutrients in our food to digest and nourish our bodies.
That happened about 2.4 BYA, the date at which we find the first fossil evidence of bacteria written into the rocks. From those ancient life forms right on up to dinosaurs, birds, mammals and early hominids, most of that we know has been gained through the business of digging up their fossilized bones and, occasionally, other body parts. Since the remainder of this chapter relies mainly on fossil evidence, we should be clear on what is meant by the term “fossil.”
A fossil is a remnant or trace of a once-living organism, such as a bone, tooth, shell, footprint or leaf imprint, that is left embedded in rock long after the organism died. Hard teeth and shells may survive millions of years without fossilization, but most softer tissues decay very quickly unless special conditions are present. Fossils typically are created by processes of mineralization in which the soft parts decay, water carrying dissolved minerals seeps into the remaining bones or cavity, and leaves the minerals to crystallize and harden in the shape of the remains. In a similar alternative dissolved minerals literally take the place of bones as they dissolve in the water, thereby retaining the original shape. Whole skeletons can be preserved in this manner, though bones typically will have been scattered by scavengers.
Unusual rare situations may preserve soft body parts, as when an insect was trapped and became encased in amber. Much is learned by studying such fossils, as well as imprints of feet, leaves, and worm tracks laid down in ancient mud and preserved by later overlayment of mud or silt. Some of the most intriguing finds of recent times have occurred in northern China where ancient species, in transition from dinosaurs to birds, fossilized in such detail that feather details can be clearly seen. Even bacterial fossils have been revealed under microscopes.
Who begat whom? In the Old Testament are found many verses purporting to tell the names of many generations from Adam on down. For example:
Genesis 5:3 And Adam lived an hundred and thirty years, and begat a son in his own likeness, and after his image, and called his name Seth; [Of interest, notice once again that business about “in his own likeness and after his image.” It clearly means that since Adam was already created in God’s image, Seth too bore God’s image. And that means that all the rest of us today, being (allegedly more or less) descended (evolved) from these people, also are yet today “in God’s image”…whatever that word “image” may mean.]
Genesis 5:4 And the days of Adam after he had begotten Seth were eight hundred years, and he begat sons and daughters;
Genesis 11:25 And Nahor lived after he begat Terah an hundred and nineteen years, and begat sons and daughters;
1 Chronicles 6:11 And Azariah begat Amariah, and Amariah begat Ahitub;
Nehemiah 12:10 And Jeshua begat Joiakim, Joiakim also begat Eliashid, and Eliashid begat Joiada.
There’s quite a lot more like this but, be assured, it pales to insignificance beside the taxonomy of begats laid down by evolution. The Biblically reported longest lived man, Methuselah, allegedly reached a ripe old nine hundred and sixty nine years. The “generations” of evolution, measured as the time over which one species comes into existence, evolves and transforms into a different species, are commonly measured in millions of years – though, as Squeak Beak showed us, a significant change can occur quickly over a single season, from one generation to the next. And too, some species evolve faster than others. Certain small insects may evolve over months or even weeks. Some bacteria, such as those growing immune to penicillin’s power to kill them, can do it by the day. But the taxonomy of evolving life that has been begat generation after generation since that first-ever life and down to the present day, presents a colossal number of begats, far too many to try to write down. Even the big shortcut of giving names to species instead of individuals is still way too long to write down.
And that is what we are concerned with here: not the small short-term changes, such as beaks, but the bigger picture whereby whole species change into whole other different species. This course is interesting because it is so seldom presented to people who might otherwise become actually interested in better understanding biological evolution. Natural speciation is precisely where most arguments are directed by those uninformed who choose to disbelieve evolution’s reality. The person who vehemently declares “I don’t believe Man came from monkeys” should not be simply dismissed, for the very statement – by missing the whole point – self evidently reveals complete absence of understanding in this important area of accumulated human knowledge.
Ignorance of evolution, compounded by narrow and closed mindsets on the subject, educationally disables a majority of the United States population. How then can we expect them to rise to consensus on shared civic values? Where even one lacks knowledge and understanding, we are all held back.
Evolutionary descriptions most commonly seen, when the subject of evolution is popularly seen at all, typically include a summary description of evolutionary mechanics, perhaps accompanied by a graphic of the “tree” of life – the whole leaving the learner barely informed if not justifiably unconvinced. Understanding of biological evolution is often elusive unless the learner is enabled to develop a tangible “feel” for the unfolding drama of a continuum that is never-ending, along with some details on how each and every species is but a transient, passing segment of the continuum – a temporary work in transition from the different species out of which it emerged toward the different future species it is evolving to become.
Though the following brief march through the last half billion years of life evolution may zigzag a bit, it is intended to convey a sense of passing time, of logical sequence from the earliest to the latest. This sampling approach is necessary because telling the full story is quite impossible – it is far too much to try to tell, even if we yet knew all the facts. One sometimes encounters the estimate that the millions of species alive on earth today represent only perhaps two percent of all the species that have ever lived on earth – the other ninety-eight percent having gone extinct. Acknowledging this little difficulty, I hope to convey that tangible feel for the continuum of more primitive, less complex creatures slowly but ever evolving into less primitive, more complex creatures. And in all of it, with rarely a backward exception, the overall trend is ever upward, to something higher – an upward “urge” all we evolving creatures feel, toward which we are drawn.
Among the various authors’ whose writings influenced this chapter, I wish to acknowledge especially Simon Conway Morris and Donald R. Prothero; their wonderfully lucid descriptions and explanations on evolution and emergence greatly contributed to my tracings of evolutionary history and the context in which I have placed it. Where statements or emphases in this chapter may differ from what they and others who understand emergence have said or intended in their writings, such differences are purely my own responsibility.
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…to be continued in one week…
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