Lonely Planets

by David Grinspoon

  and, I’ll bet, neither can you. But does that mean that such alternate

  biochemical systems do not exist, or merely that we are currently too

  ignorant or too blinkered by our assumptions to imagine them? We

  should not confuse the limitations of our own tiny intellects with limi-

  tations on the creativity of Cosmic Evolution. Our universe is full of

  varied environments and we have no idea what kinds of chemistry are

  occurring, no inkling of what’s crawling in alien seas of unknown com-

  position.

  Our evolution has expertly exploited the idiosyncrasies of carbon

  and water. After 4 billion years of adapting to and building on these

  peculiarities, of course these materials seem pretty special to us. We are

  built of carbon molecules, floating in an ocean of water. We still live in

  that ocean, only now we carry it around within our cells. You can taste

  it in our blood, sweat, and salty tears. How might this immersion warp

  our perspective?

  We have many ways of justifying our “carbaqueous” assumption,

  but sometimes I wonder if the real motivation is not simply that we’d

  be lost without it. With it we have narrowed the scope of possibilities

  enough so that we may apply science to the problem. Once we’ve nar-

  rowed life’s needs down to one condition—water—we can look around

  the universe for water worlds and apply our theories toward predicting

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  where they should be found. Our “life needs water” paradigm is born

  of pragmatic necessity, not solid scientific deduction. We need it so that

  we can do science.

  That’s fine. We do have to start somewhere, especially when taking

  on a subject as wide-open as the question of extraterrestrial life. But,

  when we repeat something frequently enough, it can work its way into

  our psyches. We forget the shallow basis on which we’ve reached our

  tentative conclusion that life needs carbon and water. What started as

  an educated guess becomes a consensus reality.

  Unfortunately, the justification boils down to “that’s the way it

  works here and we can’t imagine any other basis for life.” It is like

  someone who does not know how to design watches finding an unbe-

  lievably exquisite watch, dissecting it, and declaring, “This is so per-

  fect, it has to be the only way that a watch can be put together.”

  There’s no way that we could have designed something that works as

  well as our own biochemistry, so how can we state confidently that

  there’s no other substance in the universe suitable for this kind of con-

  struction? If our metabolism and structure were based on some chemi-

  cal system other than carbon chemistry, on a planet without liquid

  water, would we know anything about this carbon potential? In many

  ways, some obvious and some subtle, our world has been remade by

  life to look like one in which carbon is the only “natural” source of real

  complexity. Whether or not this is really true, the world would seem

  this way. So we might be fooling ourselves about carbon.

  By the time any kind of life—made by any chemical system, carbon

  or not—finally evolves consciousness, it will be stunningly well adapted

  to its world, and its world thoroughly changed (as our world has been)

  by its biochemistry. This life, upon first examining the universe, will

  conclude that life can only evolve using its own peculiar kind of chem-

  istry. Curious scientists of any chemical construction would observe

  many features of their universe that seemed to confirm this view.

  I know it won’t sit well with some of my carbon-based, and carbon-

  biased, friends, but I choose to remain an agnostic with respect to the

  carbon religion. No, agnostic isn’t right. I believe in carbon. I worship

  it. Sign me up for the carbon church. I’ll show up every Sunday morn-

  ing and do the DNA dance. But to believe, must we swear that carbon

  is the true and only way, forever renouncing all other elements?

  Some scientists, coming from a biochemical background, even talk

  about what we can learn by sequencing alien DNA and comparing it to

  Is It Science Yet?

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  our own. To me this seems as ridiculous as dissecting crashed saucers at

  Roswell. Expecting to find DNA elsewhere is like expecting a Star Trek

  universe with humanoid aliens who speak English and insist that we

  join them for dinner at eight. A chemical hereditary system, like a lan-

  guage, is the result of a complex evolutionary process filled with ran-

  domness, contingency, and frozen-in accidents.

  Might life use completely alien chemical systems elsewhere? The

  question is not exactly science, because it is difficult to think of a scien-

  tific way to address it. It is really a question of natural philosophy.

  We have to be careful when stating what is impossible. Different

  chemical environments may breed unforeseeable sources of chemical

  order. And what about life that doesn’t need chemistry at all? Why not

  life on different spatial or temporal scales? Who are we to say that the

  universe couldn’t make some kind of complex, self-organizing, evolving

  structures using its gravitational or nuclear forces, forming living struc-

  tures that are too large or small for us to notice? Life at the scale of

  molecular clouds or even galactic superclusters? Why not life, and even

  civilization, at the level of elementary, subatomic particles, where

  empires that dwarf any in human history rise and fall in a nanosecond,

  at a level completely invisible to us? Life so fast or slow that we don’t

  notice it? Why not? No reason. No answer.

  Time and again we think we know more than we do. We may never

  be able to imagine an alternative kind of life, but I bet we will eventu-

  ally come across one.

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  Throughout the continuum as we know it (and a good

  deal more, as we don’t know it) there are cultures

  Image unavailable for

  that fly and cultures that swim; there are boron folk

  electronic edition

  and fluorine fellowships, cuprocoprophages and

  (roughly speaking) immaterial life-forms which swim

  and swirl around each other in space like so many

  pelagic shards of metaphysics. And some organize into

  super-entities like a beehive or a slime-mold so that they live plurally to

  become singular, and some have even more singular ideas of plurality.

  —THEODORE STURGEON, The Widget, the Wadget, and Boff

  G A I A : I S E A R T H A L I V E ?

  Using a natural philosophy approach, perhaps we can study life’s uni-

  versals without simply projecting visions of our own kind out into the

  cosmos. Two controversial new fields of thought promise to help lift

  astrobiology beyond this conundrum of self-reference. These are the

  Gaia hypothesis and complexity theory.

  The Gaia hypothesis, named after the Greek Earth goddess, was first

  proposed in the mid-1970s by James Lovelock, a British atmospheric

  scientist and inventor, and American microbiologist Lynn Margulis.

  Margulis is the
mother of serial endosymbiosis theory, which states that

  major evolutionary innovations occur when more complex forms of life

  arise out of symbiotic collectives of smaller organisms (as described in

  chapter 8).

  How far can we extend this principle? Gaia scientists regard Earth in

  its totality as one giant superorganism incorporating many parts of our

  planet that traditional science sees as nonliving.* The atmosphere and

  *Though many older, prescientific traditions have long perceived a living Earth.

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  oceans are the breath and blood, and the rain forests the lungs of this

  great global beast. Human culture is, perhaps, its awakening mind.

  Gaia suggests that life is seen as not merely incidental, but integral to

  the evolution and functioning of the planet. Gaia is a theory of biology,

  but also one of Earth history, geochemistry, and climate. The Gaian

  approach toward the Earth sciences is “geophysiology,” studying

  Earth’s functioning and health as a physician might approach a patient.

  In 1988, as a graduate student, I attended the first major main-

  stream scientific conference on the Gaia hypothesis, sponsored by the

  American Geophysical Union in San Diego. It was fascinating to watch

  skeptical traditional scientists do battle with those from the new Gaian

  camp as they attempted to get Earth scientists to take their new

  approach seriously.* Science still doesn’t quite know what to do with

  the Gaia hypothesis, because it isn’t science-as-usual. Yet it is more than

  just a pretty metaphor. The Gaia hypothesis is guiding the way some

  biologists model life and its role on Earth, even as other (mostly older)

  biologists completely dismiss it.

  Gaia actually began as an idea about exobiology. James Lovelock,

  consulting for NASA during the design of the Viking life-detection

  experiments, was thinking about how to look for life on Mars. He real-

  ized that the unusual atmosphere of Earth is by far its most distinctive

  sign of life. In considering the global properties of life that might be

  observable from another planet, he started noticing the many ways in

  which Earth’s biosphere behaves like a giant living organism. In 1974,

  he and Margulis presented the Gaia concept in a paper called “Bio-

  logical Modulation of the Earth’s Atmosphere,” published in ICARUS,

  International Journal of Solar System Studies.

  The Gaia hypothesis has caused a quiet revolution among Earth sci-

  entists, many of whom are now realizing that life participates deeply in

  the physical evolution and functioning of Earth. A small school of scien-

  tists has fully embraced Gaia and dedicated their careers to it directly. A

  much larger group has been more guardedly receptive to the viewpoint,

  incorporating it into their work, or at least their worldview.

  The Gaia perspective views evolutionary change as a creative inter-

  play between biosphere and Earth—an intricate partner-dance between

  life and the changing planet in which neither seems to be leading. Life

  *My friend Dorion Sagan suggested that we try to get everyone to gather one morning and run down the beach naked yelling, “The Earth is alive!” but this idea never caught on.

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  on Earth is no accidental collection of organisms lucky enough to find a

  hospitable planetary home. Rather, life has largely created the world we

  know. Life, we are learning, has altered many of Earth’s basic physical

  properties, investing the air, the rocks, and the water with qualities they

  would not possess on a dead world. Thus, Gaia has important implica-

  tions for the kind of relationships that biospheres can have with plan-

  ets, and this should inform the way that we search for other inhabited

  worlds.

  With a Gaian picture of evolution we see that some properties of the

  “nonliving” parts of Earth are actually encoded in the DNA of the

  world’s organisms. Are other planets blessed with their own genomes?

  It seems beautiful and true, but is it science? Some scientists complain

  that the hypothesis is more hype than thesis. They say there is no way

  to test or falsify it. Yet, the Gaia perspective has clearly led to some

  good science and to a new framework guiding some of the science we

  were already doing. In my view, it’s right on the border of science and

  natural philosophy.

  Gaia scientists have discussed the significance of Earth’s unusual

  atmosphere, which is drastically out of equilibrium. Without the inces-

  sant, life-driven chemical cycles that permeate our world, the oxygen

  and methane would rapidly react, leaving only CO2 and water, produc-

  ing a mix of gases that we would find unrecognizable and certainly

  unbreathable. The strange brew we breathe would never be found on a

  nonliving world.

  Gaia proposes that the cumulative activity of all life on Earth acts to

  keep conditions here stable and comfortable for life. This happens by

  the evolution of numerous negative feedbacks in which the growth,

  death, or evolution of organisms creates environmental changes, which

  in turn affect the growth and evolution of other organisms. The net

  effect acts to pull the climate and various chemical balances back

  toward a certain moderate range if they begin to stray.

  Short of comparing and contrasting numerous inhabited worlds, you

  can’t do an experiment to test the idea as a whole, but you can look for

  active feedbacks on Earth that may be part of such a system. For exam-

  ple, some plankton act, collectively, as an air conditioner for the

  oceans. When the water gets warm, these guys get frisky and start mul-

  tiplying. Their growth produces a chemical called dimethylsulfide

  (DMS), which diffuses up into the atmosphere. DMS is great for seed-

  ing clouds. As the amount of DMS rises, clouds build up over the

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  ocean. The ocean surface cools off, which chills out the plankton orgy.

  The production of DMS then declines. As a result, it doesn’t get too

  cloudy or too sunny for long, and ocean temperature remains in a mod-

  erate range favored by life.

  The Gaians suggest that such mechanisms have been biologically reg-

  ulating conditions on Earth for billions of years. This homeostatic self-

  regulation makes Gaia very much like a living organism, with the atmo-

  sphere and oceans behaving like circulatory and respiratory systems.

  However, obviously Gaia is not like any other organism we know in

  some important ways. For example, it has not reproduced, although

  you can’t say we aren’t trying.

  How deeply ingrained is the biosphere in the physical functioning of

  our planet? We don’t know. Gaian science endeavors to find out. It

  could go very deep indeed. Life clearly has hold of the atmosphere and

  oceans. Numerous cycles connect the atmosphere with the chemical

  state of Earth’s interior rocks. Can life have actually assumed control of

  the plate tectonics that controls all terrestrial geology? If so, then the

  entire thermal evolution of the Earth is controlled by life.
>
  Does it really go that deep? Or might Gaia be a spherical superorgan-

  ism riding around on a nonliving core? How could you define the

  boundary dividing creature and core? Perhaps by looking for a level, at

  some depth within the Earth, where things are exactly as they would

  have been if life had never come along. When it comes to the deep inte-

  rior of the Earth, we don’t yet know if Gaia is holding the reins or skill-

  fully riding bareback.

  The Gaia hypothesis reveals life to be a planetary-scale phenomenon

  with a cosmological life span. Gaia can help us identify those global

  qualities that distinguish planets having billions of years of life

  ingrained in their cyclic chemical activity from those orbs not blessed

  by this world-altering magic.

  C O M P L E X I T Y : L I F E B E Y O N D W H A T W E K N O W

  Complexity theory is the study of self-organization in nature. You’ve

  heard of the second law of thermodynamics: things fall apart. Entropy

  will get us all in the end, leaving nothing but bland disorder. Everything

  runs inevitably downhill into dull formlessness. Yet look out the win-

  dow or stare at your hands. What we actually see around us is not a

  gray and featureless sea of entropy but a living world overflowing with

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  stunning and profligate order. What saves us from the tyranny of

  entropy is an amazing property of matter: in certain conditions, in the

  presence of a flow of energy, it self-organizes, forming ordered struc-

  tures, in seeming defiance of the second law. Complexity theory is the

  mathematical study of these emergent, spontaneous pockets of order.

  The simplest example of emergent complexity is a whirlpool sponta-

  neously forming in a flowing stream. The most complex example may

  be a living organism, or a society of organisms.

  Some scientists are starting to see life as the most refined manifesta-

  tion of a universal tendency toward self-organization. Given half a

  chance, order emerges from chaos, and given optimum conditions, mat-

  ter keeps on self-organizing until it can get up, crawl around, and write

  poetry. What I find incredibly exciting about this new field is that it

  seems to be pointing toward a mathematical account of living systems

  that goes much deeper than merely “reverse engineering” the life here