Sunday, January 26, 2014

Biogenesis: The Emergence of Life on Earth (1/26/14)

Biogenesis:  The Emergence of Life on Earth
John Shuck

First Presbyterian Church
Elizabethton, Tennessee

January 26, 2014

Genesis and Richard Dawkins
And God said, Let the earth bring forth the living creature after his kind, cattle, and creeping thing, and beast of the earth after his kind: and it was so.

And God made the beast of the earth after his kind, and cattle after their kind, and every thing that creepeth upon the earth after his kind: and God saw that it was good.

Every species is a cousin of every other.  Any two species are descended from an ancestral species, which split in two.  For example, the common ancestor of people and budgerigars lived about 310 million years ago.  The ancestral species split in two, and the two strands went their separate ways for the rest of time.

Genesis 1:24-25
Richard Dawkins, The Greatest Show on Earth:  
The Evidence for Evolution (New York:  Free Press, 2009), p. 254.

I ended last week’s sermon like this:

If you were able to time travel to 500 million years after The Big Thwack, to about four billion years ago, you would visit a blue and gray Earth.   You could bring your towel and lie on a beach.   Nothing green.  No trees, no grass, no fishies.   It would be quite beautiful though.  You would have to do without breathing.   There would be no oxygen in the atmosphere.  The nitrogen and carbon dioxide would suffocate you in a minute.   But other than that it would be nice.  A blue-gray lifeless Earth waiting for another random event. 

I should clarify something.  Random is a tricky word.   What appears random is actually subject to the laws of physics and chemistry.   There may be true randomness at the quantum level.  Physicists can debate that.    What appear to be random events often are events beyond our ability to calculate or predict.    That does not mean things happen without rules.

Mix natural laws, the energy of the cosmos, and billions of years and what emerges is beyond imagination or prediction.   You couldn’t start with the Big Bang and predict Miley Cyrus.  Nonetheless Miley Cyrus, you, me and the Super Bowl all eventually emerged after 13.7 billion years of natural law, energy, and time.   We might think of it as random, but it is not really random, it is just not pre-planned or designed. 

That amazing, unplanned, unintentional, non-designed, evolutionary unfolding is an awe-inspiring, sacred story.   It can be for those who ponder it, deeply spiritual.   In a previous sermon I called it the spirituality of randomness because it feels like that, but it is really the spirituality of natural law acting on matter and energy over time.    In that spirit Robert Hazen in his book, The Story of Earth, quipped: 

“That’s why we say if God created life, she’s smart enough to use evolution.”  P. 147

Christians have given great weight and authority to the Bible.  It has contained the story of the universe and the meaning of humankind and has provided that for two thousand years.    Some of us, who with deep appreciation for the Bible and who continue to study its human wisdom, realize that the most sacred story of life is not found in texts but in rocks.    

I personally couldn’t tell you the difference between one rock and another.   I find myself amazed when I read Hazen’s book about how scientists are able to date rocks and discover their chemical composition and through that tell us Earth’s story.    It is of course not a finished story.   They are debating and discovering new things by the moment.    We don’t have to be scientists to appreciate the story, although the more we learn, the more we can be amazed.    Similarly, you don’t have to know Hebrew and Greek and the nuances of textual criticism to appreciate the narrative of the Bible.  The more you do know, the more interesting it becomes.   The point is you don’t have to be biblical scholars to appreciate the narrative of the Bible.  You don’t have to be geologists or biologists to appreciate the narrative of Earth and the evolution of life.   

I am proposing that the story of Earth and the story of the evolution of life be given canonical status in the life of the church.  It is a Sacred Story, a Holy Word.   As preachers have waved their bibles and admonished you to read God’s Word daily, this preacher says, yes read your bible, critically, but give at least equal time to the story of Earth, our home, and to our cousins, the flying ones, the finned ones, and the four-legged ones, and the to trees, plants, and fungi, with whom we all share a common ancestor, an Adam and Eve, if you like.    The story of Earth and of the evolution of life on Earth is our soul story, our spiritual story, our God story.

Last time I left you on a rock, on a beach on a blue and gray Earth.  No oxygen in the atmosphere, no plants, fish, birds, bugs, no life whatsoever in land, sky, or sea.   That was Earth on its 500 millionth birthday, about four billion years ago.    A lot has happened since then.

Scientists don’t know when life evolved or how, but the question of the origin of life of Earth is a big one and is one that is being addressed from a number of different angles.  One of the challenges is to make a definition for life.    NASA has projects to explore candidates within our own solar system for signs of life.   You have to have some kind of definition before you know you found it.  

Gerry Joyce of the Scripps Research Insititute created this definition for NASA: 

“Life is a self-sustaining system capable of incorporating novelty and undergoing Darwinian evolution.”

Life copies itself and evolves.    Life makes stuff (metabolism) and transfers information on how to make stuff (genetics) from one generation to the next.  

Earth had the stuff of life.  It had energy from the sun and from below the crust.  It had the chemistry of life, all the elements of the periodic table, and natural law set the reactions in motion.   Earth produced lipids, sugars, and amino acids, the building blocks of life, but it took a lot of time, and countless, countless chemical reactions before that first self-replicating microbe said, “Hear me roar.”

Somewhere between 4.4 billion years ago and 3.5 billion years ago this happened.  Whether you go with the earlier number or the later number depends on whether you think life can happen more commonly or is more rare.    We don’t know if life is common or rare in the universe.  So far, we have only found it here.   Of course, we have not been able to look that extensively, yet. 

How might it have happened?   In 1953 Stanley Miller and Harold Urey did an experiment with an electric spark simulating lightning and hot water and simple gases simulating Earth’s early oceans and the atmosphere.   This experiment produced a gooey organic sludge.   Eureka!  Not life, but the building blocks of life. This was pretty exciting and this became the primordial soup theory. 

Since then, there have been alternate theories.   One is that life emerged deep beneath the ocean where volcanic eruptions have created these “deep-sea black smokers.”   Robert Hazen and his colleagues created an experiment to mimic this deep sea pressurized and heated volcanic zone that interacted with mineral surfaces.  They, like Miller also produced amino acids, lipids, and other building blocks.   

The building blocks of life are not life.  It takes natural laws, energy, and time, lots of time and lots of reactions to get to the point at what we call life emerged.   This is far too complex for a laboratory. Robert Hazen writes:

On its own, no such natural experiment with minerals and molecules is likely to have generated life.  But take countless trillions of trillions of trillions of mineral surfaces, each bathed in molecule-rich organic broth, and repeat those tiny natural experiments over and over for hundreds of millions of years.  Earth must have eventually tested virtually every combination of small molecules somewhere, sometime.  The tiny  fraction of all those molecular combinations that wound up displaying easier self—assembly, or developed a stronger binding to mineral surfaces, or enjoyed greater stability under the high temperatures and pressures, survived, possibly to grow, possibly to learn new tricks.  P. 141.

Eventually a collection of molecules started copying itself.   Evolution is about variation and selection.  Life systems are able to evolve because they produce a variety of configurations and some of those are more likely to survive than others.    Molecules that copied ate the other guys and survived.

On Earth’s one billionth birthday, life had established a hold.    The first living cell that would copy itself and would have produced brown and purple scum on the coast of continents and maybe some green slime along the equator, we could call Adam and Eve, our fist living ancestors.   That is our spiritual and sacred origin story. 

But it would take another 1.5 billion years for life to learn a new trick, that is to exhale. 

The Great Oxidation Event in which the green slime through oxygen-producing photosynthesis would forever change Earth’s surface.    On Earth’s 2.5 billionth birthday, Earth changed its color to rust as this oxygen interacted with iron.    Earth might have appeared the color of Mars with blue oceans and rust colored continents.   The atmosphere at this time might have one percent oxygen, not enough for us to breathe.  

It would take at least another billion years for the next interesting event.   

Close to Earth’s four billionth birthday, the climate started to change.   Previous to this time, the climate was fairly stable, and life in its microbial form is hanging on. But about 750 million years ago, the big continent begins to break up, making more coastal lines where the algae is able to flourish producing more oxygen.   The biomass and the gases it releases changes the climate.   The planet changed significantly and rapidly from snowball to hothouse and back again.    For a time, there was snowball Earth in which ice a mile deep covered Earth from pole to equator.    

Earth from outer space over its history would have changed from black with red volcanic stripes in the hadean period, to a blue ocean, to blue and gray when the continents first emerged all within the first five hundred million years.  Over the next 3 billion years  it wouldn’t have appeared to have changed much in appearance until the Great Oxidation Event and the eventual rust color of about 2 billion years ago.   Then the rollicking climate changes from hot house to snowball would have greeted the alien visitor with a white ice colored globe.

This process of cooling and heating due to changes in greenhouse gases eventually led to an increase in oxygen in the atmosphere around 650 million years ago.    This paved the way for the first animals and plants.    The first multi-cellular organism appears in the fossil record about 630 million years ago just after the second global snowball melted.   

From 580 million years ago, we have fossils of soft-bodied animals, ancestors of jellyfish and worms.    If life began 3.5 to 4 billion years ago, it took 3 billion more years to get to worms or worm-like guys and dolls.   It is only then that we could travel back in time with our beach towel and breathe the air.   

It was the rapidly changing feedback loop of greenhouse gases in the atmosphere that led to the expansion of life on Earth.   Now we are entering another period of climate change when again positive feedback loops are changing the climate.   Greenhouse gases such as Carbon Dioxide and Methane enter the atmosphere causing increased melting of glaciers.  Those glaciers reflect the Sun’s light.  Without them more of the Sun’s energy is absorbed, raising sea levels, melting more glaciers, releasing more methane.   As we burn fossil fuels and clear cut our forests we release more Carbon Dioxide into the atmosphere and contribute to this feedback loop.    

We ought to consider our Sacred Story.  We ought to learn the lessons of Earth’s story.   The story of Earth is the story of Life interacting with land, sea and air.   Life shaped Earth as Earth shaped Life.   We change it as it changes us.  It is ironic that climate change led to Life as we know it, from single-celled critters to Miley Cyrus and the Superbowl.   It is also true that climate change could end Life as we know it. 

That is human life.  Of course, Earth will spin.   We don’t need to save Earth. Because of natural laws acting on energy and matter over time, whatever life remains after humans have left their mark will evolve along with the Earth itself.   Those hardy little microbes, that brownish purple scum could be Life’s sole representatives again as they had been for three billion years.  

We, on the other hand, are a fragile species.   I vote for humans.  I like humans.  We are the consciousness of the universe able to tell its story, to live, to laugh, to make love.  I want us to be around for awhile.

We are in relationship with Earth and its climate.  It is an intimate relationship.   It is a spiritual relationship.    I can think of no relationship more spiritual or more worthy of our concern. 

We might want to learn Earth’s story to understand our place in it, and perhaps be inspired, to the degree that we have the power, to save ourselves.


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