Posts Tagged ‘geologic time’

UNDERSTANDING EVOLUTION by the not-so-reverend bob

Saturday, January 23rd, 2010

I want to offer you a key to understanding the scientific theory of EVOLUTION.  The key to really understanding evolution is opening our minds to the concept of geologic time.

Through most of our human history, we have only had to deal with measures of time that were important to our survival: the day, the season, the span of a lifetime.  Anything beyond the years we might live was either the distant past, or the unknowable future.

Early attempts to determine the true age of the earth and the length of human history used the Bible.  By assigning a certain number of years to each human generation described in the genealogies of the Old Testament, early scholars arrived at an estimate of some six thousand years from the time of earth’s creation to the time in which these estimates were made.  (Six thousand years may be a long time, but it is a length of time we could grasp).

But with the rise of science and the ever-growing number of discoveries in geology, genetics, astronomy and biology, our modern brains are suddenly confronted with concepts and measurements that can literally make our heads hurt.  And while we struggle to make sense of atoms and cells and viruses that are within our bodies, but which we cannot see with our own unaided eyes, we are also overwhelmed by measurements of time that have moved the age of the earth back into the darkness of history far beyond six thousand years.

HOW OLD IS THE EARTH?

We now know (from the geologic evidence) that the earth began to form some 4.5 billion years ago, or 4, 500 million years.

Thousands of hundreds of millions of years.  To minds that live by minutes, days and months (that might in one lifetime add up to a hundred) we might as well call such millions of years “eternity” or “infinity”.

In fact, we do call them just that.  Often we invoke God as both explanation and answer, as if the past were a black hole in the wall of our cozy little house disturbing us with its vastness each time we walk past it.  (The darkness of space and deep time is a frightening thing to behold and it sends a chill up our back each time we think about it).  So it’s little wonder that we sometimes hang an image called “god” over the hole to cover it up — to get it out of our mind.  But that action does nothing to answer the question and it doesn’t make the past eons go away (for even the concept of “god” makes us consider infinity and eternity).  And so time (on this scale) is something we cannot escape.

So, if we can’t escape it and if we can’t cover it up, what do we do with it?  We work towards a way of understanding it.

And we need to understand it, for there are many who doubt evolution because they can’t see it happening in the time scale of their own lives.  They wonder why they don’t see monkeys at the zoo changing, day by day, into humans.  To this we have to explain two principals from the theory of evolution:

BASIC PRINCIPLES

The first: INDIVIDUALS DON’T EVOLVE: POPULATIONS DO.  The inherited traits and genetic mutations that make up the process of evolution occur as organisms reproduce and create new offspring: genetic mutations accumulate over time as environment and the challenges of daily living naturally select the individuals that are most suited to survival in a given place and time.

The second:  TIME.  Small changes in each generation over many, many generations lead to dramatic changes in the traits of living organisms:  Whales evolved from four-legged animals that walked on land and modern birds evolved from dinosaurs.

Wildly impossible feats if you think that the earth and all its creatures have been around for only six thousand years.  But once you realize just how much time life had to get started, and then how much time it had to evolve, evolution can at last be appreciated for the astonishing explanation it supplies us for understanding life on earth.  So let’s try to understand just how long this has been going on.

THE TIMELINE

TimelineGraphicFin

I will try to assist by using some of the tools that I used to understand geologic time.  To do that I will use three pieces of lumber and a tape measure.

Let’s imagine laying three 8-foot long 2×4 boards end to end.  That gives us 24 feet of lumber for our “timeline”.  The “big bang” that spawned our universe occurred some 13,000 million years ago, but our earth formed only 4,500 million years ago, so let’s start with that number and divide 4.5 billion (or 4,500 million years) by 24.  Now, each foot of lumber represents 187.5 million years starting on the left end (at 4.5 billion years ago) and ending at the right end (the present).

At the tip of the first board, the earth begins to form (4,500 mya); where the first board meets the second board, earth’s first landmasses form at about 3,000 mya.

So, we’re already on the second board.  Where is life?

There is fossil evidence to suggest that light-reactive bacteria were around as early as 3.8 billion years ago – which means it may have begun evolving as much as 4 billion years ago.  But, the earliest definitive fossil evidence for complex, multi-cellular life shows up at 1.2 billion years ago. (Another 6.4 feet onto the second board).

So from the earliest dated rock to the earliest definitive fossil of a complex cell: Three point three four billion years pass.  Three thousand three hundred and four thousand million years (more than half of our “timeline”) passed for life to begin (or 18.13 feet from “the beginning”)

Six hundred fifty-seven million years later, during the “Cambrian Explosion” life starts developing shells and hard parts.  (580mya, or only 3.93 feet from “today”).

Fifty million years after that (or about 3.2 inches): the first known footprints are made on land.

Another three inches or so (or 55 million years later): Primitive plants appear (followed later by insects, sharks and seed-bearing plants).

Then about 290 million years ago: (a foot and a half from today) Dimetrodon – a pre-mammalian reptile — leaves his muddy footprints on the Permian shoreline.  But then: (252 mya 2.5 inches later) The Permian-Triassic extinction event.  70% of all life on land and 95% of life in the oceans are wiped out.

Life recovers.  Like it probably had before, the fossil evidence suggesting this was not the first major extinction event.  Life recovers in a big way.

THE AGE OF THE DINOSAURS

The impressive one hundred sixty-five million year reign of dinosaurs covers about 10.25 inches of board.

That means that a Tyrannosaurus Rex living in the late Cretaceous (the last of the Dinosaurs) could have tripped over the fossil of a Jurassic Stegosaurus that had been extinct already for millions of years.  Dinosaurs were walking on the fossils of earlier, extinct dinosaurs.

During their reign the first viruses appear, as do flowering plants.

Then 65 mya (About four and a half inches ago): The Cretaceous-Tertiary (KT) Extinction event.  Dinosaurs and about ½ of all species are wiped out.

35mya Grasses evolve.

About 5 million years ago we split off from our last common ancestor with the other primates (and no, Evolution doesn’t say we descended from a chimp — that would be like saying you descended from your own distant cousin — but it does show chimps and humans shared a distant common ancestor).

Then — some 200,000 years ago — the first anatomically modern humans appear (us without a shave and a suit).

50,000 years ago we inhabit Europe.

25,000 years ago the last of the dead-end branches of our hominid family tree, our distant cousins the Neanderthals die out.

10,000 the Neolithic: Our modern history begins.  Tools, art, language, and then you and me.

After 4.5 billion years of bubbling, rumbling, profligate evolution and extinctions (large and small) here we are — our entire human history occupying less than the last 1/64th of an inch of earth’s 24 feet of history.

So that’s how long it took for us to get here.  That is how much time life — you and I — had to evolve.

I hope this helps you understand evolution, and helps you appreciate how amazing it is to be alive right here and right now.

– the not-so-reverend bob

MY FAMILY TREE By the not-so-reverend Bob

Saturday, January 2nd, 2010
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The not-so-reverend bob with two Neanderthal and one modern human skull.

NOTE: This “sermon” was presented with the aid of a timeline mounted on the wall which represented “geologic” time.  To offer the reader a sense of this visual aid, you can imagine three 8-foot long boards laid end to end, with each foot of length representing 187.5 million years.  At the tip of the first board, the earth begins to form (4,500 mya); where the first board meets the second board, earth’s first landmasses form (3,000mya); roughly 5.4 feet past that point (we’re now well onto the second board), the first multi-cellular life appears on earth.  The first dinosaurs don’t appear until just over 1 foot from the very end of the very last board; with the first anatomically modern humans (us) appearing less than 1/64 of an inch from the end of the final board (the “tip” of which represents the present).

And now the SERMON as originally read during “Happy Birthday Charles Darwin at the Church of Evolution with the not-so-reverend bob” on February 12,13th 2009 at The Black Box Theater in Las Cruces, New Mexico:

“In the last paragraph of the his Origin of Species, Darwin wrote this:

It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; Inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

One day I decided to draw my family tree.  I took a big piece of paper, and started drawing lines and brackets, beginning with me, then up to my parents, then to their parents, and so on with a space for every one of my ancestors.

I ran out of room.

Oh – wait – I only really have to make spaces for the ancestors I know about, and I only have one line that goes back really far, and the other lines peter out pretty fast, so…but what about all those empty spaces I don’t need.  What about the names I don’t have to make room for?

How many unknown ancestors do I have?

There’s a mathematical answer to that. The numbers increase geometrically, each generation being multiplied by two. I have two parents, and they each two parents which means four grand-parents, and then 8 great-grand parents, 16 great-great grand parents, and so on.

To give this perspective, my famous ancestor standing on Bunker Hill shouting “Don’t shoot until you see the whites of their eyes!” was one of 64 ancestors of mine living at that time.  When I go back to the farmer in Salem before the witch trials, he is one of five hundred-some.  And if I keep going to the knight living in England in the middle ages, that gentleman was one of 1 million and some change.

Go back a few more generations to his ancestor in the boats with the Normans, and he is one of 1 billion of my great great whatever grand parents.

A billion ancestors in less than one thousand years of history.

Were there even that many people living on the planet in 1066?  Nope.   There were about four hundred million.  We didn’t bust a billion until 1820.  This was my moment of clarity, where I realized that — mathematically speaking — there had to exist a point where the number of my ancestors would match the number of humans alive on the planet at that time in history. Mathematically at least — I was related to EVERYONE, and everyone was related to me.

I was hoping to find out more about who I was by looking at where I came from.  Everyone wants to know who they’re made of.  But how meaningful is it, really, if I am only one sixty-fourth Revolutionary war hero, or one one-billionth Norman conquerer?

Especially when I only know the name of one of that one billion?

That was a bit of a reality check on our search for famous ancestors.

I was discouraged and out of ancestors until science gave me an opportunity to go further.

I get my DNA tested, to see what that tells me…see if my height really did come from the milkman.

DNA testing follows a single thread through time  – mother to mother to mother or father to father to father. DNA confirmed what the names on my family tree had told me.  Good.  No Milkman.  But it added this:  My blood group was among those passed down from the first group of modern humans that occupied Europe around 50,000 years ago.

If I’ve got a billion ancestors in 1,000 years, how many do I have at 50,000?

Here’s where the math stops being useful.  The original population of humans that occupied Europe was small…we don’t know how many were in the first wave…10,000?  50,000?

Now it is a fact that all of my nameless ancestors existed – they were alive in their times.  They reproduced and passed their genes on to the next generation.  But for almost all of those ancestors — I will never have a name or a face.

These are the “gaps” in my “fossil” record.

This time I was really out of ancestors.  Or was I?

MITOCHONDRIAL EVE:

Mitochondrial DNA – which is DNA that remains un-changed by reproduction, mutates at such a slow rate that this rate of mutation can be used as a sort of “clock” to determine when populations split.

This DNA – which is passed from mother to daughter – tells us when Europeans left Africa by sampling certain African populations and comparing the mutation rates of their MTDNA with that of modern Europeans.

But when geneticists began comparing DNA samples from people all over the earth, they were startled by the result:  fundamental similarities in mitochondrial DNA in living humans suggest that we all contain genetic material from a single woman who was living in Africa around 200,000 years ago.

Scientists rather dramatically named her “Mitochondrial Eve”.

But this Eve wasn’t living in a garden.

What this suggests is that there was a serious bottleneck in the human population at that time, and if not for the reproductive success of this woman and her family, we might very well have become one of the other 99% of all species that have ever lived that became extinct.  We came that close.

So this must be where my family tree ends?  Nope.  What’s next?  Evolution.  And if you’re going to understand Evolution – I found out — you’ve got to understand how long it’s been at work..

We’ve been a long time in the making…a long time.

How long?

Not just 50,000.  Not even 200,000 years.

Let’s say this tape measure represents geologic time.

Geologists tell us that our universe began – the big bang – around 13.7 billion years ago.  Well, my tape’s not that long, so let’s begin with earth, which began forming a more recent 4.54 billion years ago.

This end represents the first days of our young planet, and the other end represents right now.  I’m gonna start over here, at 4.5 Billion years ago, and start to walk towards now, and I want you to shout out when I get to the point where life began.

It’s kind of a trick question.  For although there is fossil evidence to suggest that light-reactive bacteria were around as early as 3.8 billion years ago – which means it may have begun evolving as much as 4 billion years ago, the earliest definitive fossil evidence for complex, multi-cellular life shows up 1.2 billion years ago.

From the earliest dated rock to the earliest definitive fossil of a complex cell: Three point three four billion years.  Three-thousand three hundred and four thousand million years passed for life to begin.

The fossils, by the way, were red algae. They were having sex.

Six-hundred fifty-seven million years later, life starts developing shells and hard parts.  (580mya — The Cambrian Explosion).

Fifty-million years after that: the first known footprints on land.

55 million years later Primitive plants.

Insects, sharks and seed-bearing plants

Then about 290 million years ago: Dimetrodon – a pre-mammalian reptile — leaves his muddy footprints in the Robledo Mountains.  But then: (252 mya) The Permian-Triassic extinction event.  70% of all life on land and 95% of life in the oceans are wiped out.

Life recovers.  Like it probably had before, the fossil evidence suggesting this was not the first major extinction event.  Life recovers in a big way.  A really big way.  Like, Dinosaur big.

The age of dinosaurs, 160 million years worth.

One-hundred sixty-five million years of Dinosaurs.

How do we really conceive of one hundred sixty million years?

Close your eyes, and imagine your favorite dinosaur. T-Rex, Triceratops, Hadrosaur.  When I picture a dinosaur, I see it on a sunny day, tearing some smaller creature to pieces, lapping water from a stream: it is a moment I imagine.  A moment.  Not a day, not a month, not one hundred sixty million years.

But one day I got an image that made it real for me:  One day I got the image of a Tyrannosaurus Rex living in the late Cretaceous – the last of the Dinosaurs — tripping over the fossil of a Jurassic Stegosaurus that had been extinct already for millions of years, and that image crystallized for me the reality of just how long life on earth had to evolve.  Dinosaurs were walking on the fossils of other dinosaurs.  Not to mention three-hundred-fifty million year-old fossilized trilobites!  That image stayed with me. Clearly!  I wrote a whole musical about it.

So – real quick: ‘cause I haven’t even gotten to US yet!

200 first viruses

130 flowering plants, pollen, things pick up.

Mya: Creataceous-Tertiary (KT) Extinction event.  Dinosaurs and about ½ of all species are wiped out.

35 Grasses evolve.

200,000 years ago, the first anatomically modern humans appear.

Two hundred thousand years ago: Mom.  The one human mother common to all of us living today.

50,000 years ago – as I mentioned — we inhabit Europe.  But we weren’t the first hominids there.  There were others.

25,000 years ago the last of the dead-end branches of our hominid family tree, our distant cousins the Neanderthals die out.

10,000 the Neolithic: Our modern history begins.  Tools, art, language, out of the caves.

In the blink of an evolutionary eye it’s: Greece, Rome, the middle ages, the Renaissance, the Enlightenment, the Industrial Revolution, the Wright Brothers fly, two dudes create the personal computer in their garage and – BOOM — here we are.

So that’s how long it took for us to get here.

So how did we – how did all of this — evolve from nothing?

Well…we didn’t evolve from “nothing”.  This planet formed in such a way that an atmosphere developed that moderates solar radiation, impacts of countless objects from space made us rich in metals and elements, and we were just the right distance from the sun to have liquid water, a lot of it.  That’s hardly nothing.  And we have a molten core that spins and creates magnetism that both protects us from solar winds and provides gravity.  So when we look about and see all of these creatures, including us, so fully adapted to this planet and wonder who or what could have made it so, the answer is: Evolution.  Evolution.  Given the air, water, gravity and materials at hand, how could it have turned out any differently?

Of course the air around us flows easily into our lungs, food tastes good on our tongue, we walk solidly on this earth in this gravity.  Of course.   Of course.  Of course.

This doesn’t mean the universe had us in mind when it started.  If any of the conditions had been different, we would have evolved in a different direction.  Or not made it at all.

My family tree – though vastly extended by all of this — is not complete, and can never be.  Very, very few living things leave a fossil behind, and precious few of my ancestors left any lasting evidence of their lives…or did they?  For don’t I carry in my living DNA their memory – am not I the evidence of their lives passed down from mother to daughter, father to son, from every mammal, fish and organism that ever lived in my ancestral line?

A very recent survey asked adults if the following statement was true:  “Humans share 50% of the DNA with Chimpanzees”.    2/3rds of those responding answered: “No, that statement is not true”.  Well, they’re right, in a way.  The fact is we share 95-98% of our DNA with Chimpanzees.  We share 80% with mice.  We share 40% with lettuce.

I bet you’ll look at your salad differently next time.

Because of geologists, anthropologists, geneticists, chemists and paleontologists – because of Charles Robert Darwin — I can now trace my family tree to right here: (indicate near the 4 billion year area)  Somewhere. The last universal ancestor to all life.  Not just to us humans.  No.  Somewhere in here is our last common ancestor with every living thing on the planet: The monkey, the whale, the grasshopper, the flu virus, the bacteria on our skin, the dog, cat or hamster waiting for you at home.

“… to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us…There is grandeur in this view of life…from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

We carry in our own bodies the physical proof of our long journey from fish to man.  As Darwin saw some 170 years ago:

“We must, however, acknowledge, as it seems to me, that man with all his noble qualities… still bears in his bodily frame the indelible stamp of his lowly origin.”

You and I have tailbones, we hiccup with a reflex likely left over from our amphibian past, our backs go out because we used to walk on all fours, we still grow muscles we never use that once helped us turn our ears toward sound, whales have hand and finger bones in their flippers and vestigial hip bones – left over from when they walked on land in the EOCENE only 50-million years ago.

Evolution, random mutation, natural selection.  Over and over and over and over over millions and millions of years.

And so we celebrate Charles Darwin because he looked at the evidence and saw what was there, even though science – in his time – could not resolve the exact mechanisms of evolution, or even tell him whether the earth was old enough to allow evolution to have occurred, he published his theories so the world could know them and explore and test and debate them.  In the 150 years since science has confirmed and proved and stood in awe as Darwin’s theory of Evolution has turned out to be the organizing principle to understanding the origins and diversity of life on earth.  Because of Darwin, life on earth makes sense.  Because of Darwin, my life makes more sense.

I got more than I bargained for when I went looking for my ancestors.

I look at this whole world all the other critters on it and know that I belong here by right of birth.  I can see gradations of consciousness in the other animals, and more fully appreciate the wonder that life is: “our lives no less miraculous just because they happened randomly!”  Perhaps, even more miraculous for that, and more precious.

My family tree.

I represent in my DNA an un-broken thread of life that extends all the way back to there (show).

This is my family tree.  But not just mine:

My mom and my dad, I share with my brothers.

My two grandmothers and grandfathers, I share with my uncles, aunts and cousins.

My great great great grandparents I share with hundreds, thousands of ever more distant cousins.

This mother (pointing to “Mitochondrial Eve” on the last 64th of an inch on the timeline)– I share with you, and you, and you, and you, and you….

This mother (pointing to the first multi-celled organisms 10.6 feet from the end on the timeline) – we share with each and every living thing on earth.  She belongs to all of us, and all of us belong to her.

“Fish and fowl, furry mammal and sleek snake, darting dragonfly and stippled starfish.  Life infinitely variable: each incarnation fitted — by evolution and natural selection — to his, her or its own environment.  Shark, puppy, sparrow, giraffe.  Flower, fern, seed, spore.  Bacteria, virus, germ and so much more.  The numberless incarnations of one life – one carbon based life – our life, my life, your life. Tonight let us celebrate our individual, particular, related lives and the lives of those whose living makes our lives richer, deeper, better.”

BECAUSE…(After the actual reading of this “sermon”, we then sang: “I Belong”)

LYRICS to “I Belong” (words and music by Bob Diven, copyright 2009):

I belong, like the wind like the stars, I belong.

I belong, like the words with the song, I belong.

I’m a part of each rock and every tree

I’m a twin to fish, bird and bumblebee

For the life that moves them moves in me,

I belong, I belong.

I belong, like the moon and the sun, I belong

I go on, like the moonrise, the dew in the dawn.

From the first frail life swimming in the sea,

To the bright-eyed face peering from the tree,

I’m a part of life, life’s a part of me,

I belong, I belong,

I belong in each day that marks my span

Living ev’ry moment the best I can,

I reach out to touch and understand!

I belong, I belong, I belong.

(Copyright for any commercial purposes 2010 by Bob Diven, all rights reserved.)