in myriad forms. It was a chemical Kama Sutra where molecular adven-
turers got busy, trying anything at least once. The result was a period of
“chemical evolution,” a primitive molecular survival of the fittest
where stability and longevity were the only criteria for success.
Molecules that found longer-lasting, more stable configurations were
naturally selected. Such hardy structures, favored by the gods of trial
and error, became concentrated in the primordial sea.
And then it happened. This magic moment. Carbon chemicals, inno-
cently cavorting in water, hit upon something new and extraordinary:
structures that could make copies of themselves. Eureka! In the 10-billion-
year history of the settling down of matter, and the bubbling up of order, a
powerful new force was unleashed: heredity—the preservation of useful
information. Those structures that could copy themselves most accurately
and efficiently multiplied like rabbits in a world without foxes. Self-
replicating chemicals rapidly populated the young oceans.
We don’t know what the first self-copying chemical mechanism was,
but we do know which one stuck, because it’s still here, working its
magic: DNA. In a sense, there has only ever been one strand of DNA,
dividing and multiplying on Earth for nearly 4 billion years. DNA
never dies, it only improves. Evolutionary tributaries dry up and disap-
pear, but the mainstream of DNA-driven life keeps on growing. Barring
*The Miller-Urey experiment, described in chapter 3, demonstrated that these molecules are easy to make in conditions simulating those of the young Earth.
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disaster, it will flow onward until, 5 billion years hence, our dying Sun
becomes a red giant star and incinerates the Earth. This helical miracle
may even outlive its star of birth, if we leave and take it with us.
DNA is a molecule that may have achieved immortality. And we,
along with all other terrestrial life, are its by-products, reproduction
mechanism, and life support system. We are the ships that DNA has
devised to navigate the world. But when the machines get smart
enough, they can take over the factory. With the first faint, fragile glim-
mering of intelligence on Earth, we can see the potential for a new, as
yet unwritten, chapter of Cosmic Evolution, the self-aware phase in
which matter wakes up, takes a look back at where it’s been, and con-
sciously decides how to proceed.
W H A T ’ S T H E P O I N T ?
This new origin story need not replace all others, but it does augment
them. I do not mean to be cavalier in comparing the story of Cosmic
Evolution to the world’s great religious texts. Obviously, this story does
not address all the needs met by our older origin stories. It doesn’t
answer the question “Why?” about anything. It provides us with no
rules on how we should live, at least not in any obvious way. I do not
subscribe to scientism, the view that science is all you need. If pressed, I’d say that John Lennon’s view that love is all you need is closer to the
truth. But a combination of the two is even closer.
So then, what’s the point? How does it help us if it cannot provide us
with a purpose or tell us how we ought to live? Why science’s attitude
of superiority? Well, the attitude is not justified. But there is a point.
Several, actually. Science does not tell us why we are here, but it has
taught us a lot about where “here” is. Science limits the range of the
possible and, in so doing, points us toward what is true. And I think
that a careful reading of this story does convey some powerful messages
that I, personally, am not afraid to call religious.
You, me, everything you can see except the stars, and a great deal
that you cannot, were all once mixed together in one giant, diffuse
cloud. Even the stars themselves, and all the distant galaxies imaged by
the Hubble, we and they were all one, even earlier, when the universe
was a hot little ball of fire. Once a singularity, always a singularity.
That Zen master hot dog vendor doesn’t have to make you one with
everything. You already are.
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L o n e l y P l a n e t s
Cosmic Evolution carries a message of complete and profound unity,
which I think can be read as a reason to care deeply for all things, espe-
cially for the living Earth and its creatures, the most highly evolved
local products of matter’s slow climb from formlessness. Against this
backdrop, the anthropogenic mass extinction that we are currently
inflicting upon Earth seems a desecration of cosmic proportions.
Maybe there is a moral to this story.
F I E R C E M A G I C
Last night, I was up late writing this chapter, trying to distill the story
of Cosmic Evolution into a brief narrative. I had to take years of
detailed study, throw out most of the details, and try to extract the core
events, the highlight reel of the universe. With visions of galaxies danc-
ing in my head, I drifted off to sleep and had a vivid dream. An earnest
woman who might have been Native American—she looked like the
poet Joy Harjo—was telling me about something important that had
just happened to her, something that made her realize how incredibly
fleeting our lives are. She implored me to remember to treasure each
day.
I don’t know whether this dream was related more to the cosmic
timelines ripping through my mind or simply to the emotionally mixed
experience of shutting myself off from my people and my planet for
some of my precious days to get some writing done. But, I awoke that
morning with these Joy Harjo lines in my head:
I can hear the sizzle of newborn stars, and know anything of
meaning, of the fierce magic emerging here. I am witness to flexi-
ble eternity, the evolving past, and I know we will live forever, as
dust or breath in the face of stars, in the shifting pattern of winds.
This poem expresses another lesson of Cosmic Evolution. That we
are immortal. There is life after death in a sense that is completely real
and does not require blind faith. You don’t have to see yourself as sepa-
rate from everything else. We have been here, gathering ourself for at
least 10 billion years. This is just the beginning. We’ll live on for tens of
billions more.
We can’t study life as a cosmic phenomenon without studying the
universe as a whole. The seeds of life were planted in the early primeval
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fireball, and the roots of life grow in the very fabric of space, time,
energy, and matter. What we don’t yet know is how to place ourselves
in this story. Are we peripheral or accidental, or somehow integral and
central to the main theme? The meaning will not be clear until we find
out if there are other souls circling distant stars, others who have
emerged from this same cosmos into an awareness of their own.
Either way, this is our story. It grounds our existence in the unfolding
of the universe. We carry reminders of it in every cell, every atom, of
our bodies. We have learned that our ancestors are stars. And we are
water— enclosed sacs of Earth’s salty oceans that have conspired with
carbon molecules to achieve mobility and a fledgling form of con-
sciousness. Looking out, and looking back, we see that we are the eyes
of the world and the soul of the galaxy. We just don’t know whether we
are the only ones.
Each of us, growing up, reaches a point at which we become curious
about our origins. We ask our parents challenging questions about
where babies come from and which came first, chickens or eggs. Here
on this rocky speck of living stellar afterbirth the climb of matter has
somehow arrived at what we proudly call intelligence. Here the uni-
verse has grown up to an age where it wants some answers about
its own provenance. Here on Earth, the cosmos has awakened from a
12-billion-year dream. It seems that our consciousness, in inchoate
form, was here all along, waiting for the right conditions to precipitate
out of inanimate matter. Elsewhere, is it slumbering still, or were we
among the late sleepers?
Why here, why now? Once life got started, it quickly embedded itself
in the workings of the planet, altering the atmosphere, the oceans, the
rocks, and the soil. As life has adapted to the changing environments of
the Earth, Earth has been remade continually by life. So ancient is this
partnership that it is impossible to know what Earth would have
become if it had not become alive some time around its 500 millionth
birthday. What happened on Earth to give rise to one species that
makes music, Mandelbrot mandalas, and Mars probes? How were we
transformed from a newly formed, warm, wet, organic-rich planet into
a profuse, prolific biosphere that has now started looking back out at
the planets, stars, and galaxies to piece together this story? To better
understand the context of our awakening to consciousness, and to
assess its significance for life on other worlds, we must closely examine
the history of Earth and its life.
Earth Birth
6
If seeds in the black Earth can turn into such beauti-
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ful roses, what might not the heart of man become
electronic edition
in its long journey towards the stars?
—G. K. CHESTERTON
Did I know you?
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Did I know you even then?
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Before the clocks kept time
Before the world was made
—U2, “WILD HONEY”
I N S I D E O U T
Who are we to say that our Earth is such a special place? Like parents
certain that their baby is the cutest ever born, of course we think our
planet is the chosen one. Nevertheless, in all modesty, you have to
admit: Earth stands out. Ours is the only planet around these parts able
to tell its own story.
All other local planets appear to be dumb as rocks. Somehow, our
world has sprouted eyes, hands, minds, and mouths, not to mention
microscopes, telescopes, and microchips. Since we seem to have, for
now, become Earth’s only voice, our reconstructions of geological his-
tory amount to an autobiography of the planet. Many pages are miss-
ing, scattered by the winds and crumbling with age. The story is written
in the rocks, fossils, and whiffs of ancient air. As we learn to read it, our
world begins to tell its tale.
We planetary scientists are used to taking a global view. We’ve had
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no choice, really. Holism is easiest when you know next to nothing, and
we’ve learned about the other planets from the outside in. At first we
knew them only as bright lights wandering the sky. Telescopes trans-
formed them into dusky disks with faint, suggestive markings.
Spacecraft have turned them into real places with landscapes of rocks,
dunes, riverbeds, craters, mountains, and ice. But each is still a tiny dot
in the sky that you can cover with your little finger.
When planetologists look at life on Earth, we regard our own world
as we might examine another planet in searching for signs of life. From
space we don’t see organisms, cells, tissues, and chromosomes. We see
global patterns of vegetation and habitation, and the telltale traces life
has left in the atmosphere and oceans. We look at the totality of life to
see what distinguishes our planet from nonliving worlds. The planetary
perspective allows us to see large-scale features and trends that we
might miss if we stayed mired in the details.
Because we spend our time unraveling planetary histories that have
unfolded over billions of years, ours is a time-lapse view of terrestrial
evolution. In this fast-forward movie of Earth, the coming and going of
individual species, mountain ranges, oceans, and ice ages are acceler-
ated to a blur. We see only those major transformations that would be
visible from far outside, catching the eyes (or the antennae) of inter-
ested aliens with long attention spans.
What follows in the next few chapters is a brief account of some of
the more memorable, formative events in the maturing of Earth. My
purpose is to make sure that, when we turn outward to consider life in
the rest of the universe, at least our guesswork will be educated. Like all
biographies, this will be highly selective. In particular, I’ll focus on
developments that seem to have been pivotal for the continued flower-
ing of life and eventual awakening of consciousness here, and that
might be part of the story on other worlds as well.
We won’t know anything with certainty about the evolution of life
elsewhere until we find some, or it finds us. From a cosmically enlight-
ened perspective that we do not currently enjoy, the path of life on
Earth may appear either typical or unique. Either way, it is worthy of
careful study, if only because it is the path that we ourselves have taken
from the inanimate trajectories of elementary matter, through a nested
series of communal bodies with ever subtler reflexes of survival, on into
the first sputterings of conscious awareness.
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L o n e l y P l a n e t s
B O R N I N S T E A M
As the newborn Earth grew by the assimilation of lesser worlds, her
gravitational reach extended farther into space. Stray planetesimals or
comets wandering nearby were sucked in, feeding the rocky little bun-
dle of joy, increasing her appetite for more. As the planet’s strength and
hunger expanded, approaching bodies were accelerated to ever faster
velocities and incoming rocks increased their punch. The harder they
came, the harder they fell. Mountains of rock, metal, and ice came
crashing down, each one raising a massive spray of vaporized rock and
leaving a round pool of incandescent magma.
Though Earth was dotted with newly formed craters, each briefly
heated to thousands of degrees, on the whole the planet stayed quite
frigid. In its earliest stages, the growing planet had no atmosphere at
all, s
o these puddles of molten lava were touched directly by the frozen
void of space. Some heat was buried underground, but the surface
cooled quickly, radiating away heat just as fast as the impactors could
bring it in.
All that changed when Earth began to cloak herself in steam, which
was liberated from the falling rocks themselves. Virtually all of the
boulders that assembled to make the Earth contained some water,
locked inside the crystal lattices of minerals. If you hit such a rock hard
enough, the water is knocked loose from its mineral cages. Once Earth
grew beyond a certain size, roughly half her final diameter, every new
rock fell too fast to hold its water inside. Now each impact spat out an
angry puff of vaporized water and carbon dioxide, which, bound by
gravity, began to accumulate around the growing sphere. This “impact-
generated atmosphere” was Earth’s first air. Soon our planet was blan-
keted in steam.
Water vapor is a greenhouse gas, meaning it absorbs infrared radia-
tion and helps a planet hold on to its heat. Our early steam atmosphere
formed an insulating blanket, swaddling the infant Earth. Giant bodies
from space continued to fall at cosmic speeds, but now the heat from
their impacts was trapped. The young Earth, insulated by its new steam
atmosphere, became absurdly hot, melting surface rocks, which liber-
ated still more steam. Our planet was covered by a global ocean of
molten rock and enveloped by a dense, sweltering atmosphere.
Sometime during those early, steamy days, before oceans appeared
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and life began, the young planet suffered one truly Earth-shaking
impact that, traumatic as it was, would later prove essential in building
its unique character. In the chaos of planetary growth, when the solar
system was crowded with planetesimals on crazy, intersecting orbits,
another planet, about the size of Mars, plowed into Earth. The glancing
blow blasted off a big chunk of Earth, forming an orbiting ring of
vaporized rock that later coalesced into our Moon. This apocalyptic
event melted our planet in its entirety and had major effects on its later
atmospheric and geological evolution. Ever since, the Moon has influ-
enced Earth in numerous ways, slowing its rotation, raising tides in its
oceans, steadying its spin axis and climate, and inspiring its poets and
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