Lonely Planets

by David Grinspoon

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  Multicellularity is a neat trick, but it’s not all that easy to pull off.

  Before going multicellular, a few fundamental problems have to be

  worked out. The development of a complex plant or animal always

  starts from one single, fertilized cell made from the fusion of sperm and

  egg. This zygote starts dividing like mad, producing the millions of cells needed to make a large organism. The strange beauty of this development is that somehow each cell “knows” what kind of tissue it is to

  become part of—a slice of liver, the tip of your nose, a piece of your

  heart, or a piece of your mind. How do they know?

  Some scientists used to think (quite reasonably) that the instructions

  were split up so that your toes got only the genes to make toes and your

  nose had only nasal genes. Nope. It turns out that the entire genome,

  the whole instruction manual, is present in every cell. This is why

  embryonic stem cells have such great versatility. Each dividing cell of a

  developing embryo has the potential to generate any body part. There

  is some system—which hasn’t completely been worked out yet—for let-

  ting cells know which kind of tissue they are to become. Without such a

  master control system, multicellularity would not be possible.

  This problem is solved through a multilevel genetic control system. It

  is as if there is another genome within the genome of each cell that

  somehow learns what kind of cell it is to be and activates certain genes

  (calls them to action) and suppresses others (asks them to sit this one

  out). This centralized control is quite elaborate, yet it is essential to

  have something like this in place if multicellularity is going to work.

  Difficult things do take time to evolve, but can that explain a 3-billion-

  year gap?

  Alternatively, we can ask what changed on Earth during this interval

  that may have made the leap possible or even inevitable. One thing that

  changed was the mixture of gases composing our atmosphere. Oxygen,

  good old O2, which was apparently absent from Earth’s earliest air,

  gradually increased in concentration until it became quite abundant,

  second only to nitrogen. The most common explanation for the timing

  of the multicellular leap is that it had to wait until the concentration of

  atmospheric oxygen rose high enough to make efficient respiration pos-

  sible. When you blow lightly on a flickering flame, it flares up.

  Similarly, the more oxygen there is around, the more organic fuel life

  can burn in the slow flames of metabolism. Perhaps the increased

  energy source of an oxygen-rich atmosphere was needed to power the

  larger bodies of the metazoa.

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  Where did all this bountiful O2 come from? Life made it as a way to

  avoid starvation. The history of oxygen on Earth is one of life coevolv-

  ing with the planet.

  L E T T H E M E A T L I G H T

  When life first formed, finding a meal was not a problem since the early

  Earth was loaded with organic molecules. But this paradisiacal situa-

  tion, with tasty molecules everywhere for the taking, could not last. As

  the food supply became depleted, a new long-term, reliable food source

  was crucial for the continued survival of life on Earth.

  Fortunately for us, before it was too late, life evolved the trick of

  photosynthesis—using the energy of sunlight to make organic food.

  This had to happen fast. Otherwise, when all the leftover crumbs were

  gone, the party would have been over. Life would have perished, unless

  it found a way to mooch off the geothermal energy coming out of sub-

  marine vents or other exotic sources. But Earth life is almost entirely

  solar-driven. Had life not developed photosynthesis early on, our planet

  would now be unrecognizable, and there might well be no one around

  this part of the galaxy capable of recognizing anything.

  Photosynthesis is so pervasive and essential to life on Earth that it is

  not inaccurate to describe the biosphere, as did Russian biogeochemist

  Vladimir Vernadsky in 1926, as a continuous, thin film enveloping the

  planet, within which sunlight drives matter through incessant transfor-

  mations. In other words, life is something the Sun does to Earth. Earth

  life is the way (or at least one way) that our star has found to express

  its biological potential. We are the life of the Sun.

  Photosynthesizing microbes began ripping the H out of H2O, com-

  bining it with carbon to make organic food, and spitting out O2 as

  waste. Even so, at first oxygen did not build up in the air. Everybody

  loves oxygen, and many other elements were in line for its favors. The

  young Earth had lots of iron, which is an oxygen hog if ever there was

  one. For hundreds of millions of years, most of the photosynthetically

  released oxygen went into oxidizing Earth’s iron, which was constantly

  showing up in volcanic flows fresh from the interior, always demanding

  oxygen. There was also methane (CH4) from volcanoes, methane from

  bacteria, ammonia (NH3) from lightning storms, and other hydrogen-

  rich gases, all composed of elements that eagerly forgot their other

  dance partners the moment oxygen entered the room.

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  There was always more than enough water to go around, and plenty

  of sunlight. Life went on using both and leaving oxygen behind.

  Eventually, the world’s thirst for oxygen was sated, or at least the

  demand leveled off. Finally, free oxygen started ever so slowly to build

  up in the atmosphere.

  Hallelujah!

  Except that this was a terrible disaster.

  Oxygen is dangerous. Because of the promiscuous reactivity of oxy-

  gen, no organic molecule is safe. Rust never sleeps. Have a little fire,

  scarecrow. Oxygen was poisonous to organic life. The buildup of oxy-

  gen was Earth’s first global environmental crisis, and life brought it on

  itself. At first, it seemed as though the careless photosynthesizing

  microbes had really screwed themselves, with their shameless oxygen

  emissions causing global change that threatened their own extinction.

  L I F E E X P L O D E S

  Catastrophes, viewed from a different angle, are often opportunities.

  It’s true that oxygen reacts ferociously with organic molecules. It’s also

  true that these reactions release a lot of energy. Uncontrolled, this

  energy will burn you up. But life, turning adversity into advantage,

  found a way to harness fire: respiration, which uses controlled oxida-

  tion to constantly charge its batteries. Aerobic life was born.

  When respiration started, oxygen was still only a minor trace gas in

  our atmosphere. Over billions of years, it gradually built up until it

  reached its present level about 1 billion years ago. Since then, it has had

  minor ups and downs but has not strayed too far from 20 percent of

  the air we breathe.

  The buildup of oxygen in Earth’s atmosphere had another tremen-

  dously fortunate and enabling side effect: it made the ozone layer. Once

  there was enough oxygen in the air, ultraviole
t light started splitting O2

  and recombining it in various ways in the upper atmosphere. A by-

  product was the production of O3 (ozone). Ozone happens to absorb

  the same wavelengths of solar ultraviolet light that are fatal to our kind

  of life because they destroy complex organic molecules. Before ozone,

  life mostly hid under the surface layers of the ocean, where water

  absorbed harmful UV. Now it was safe to colonize the land.

  Like an athlete trained at high altitude coming down off the moun-

  tain, life reveled in the ever richer air and revved up its metabolic

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  engines. But if more O2 allowed the possibility of bigger living crea-

  tures, you would never have known it for most of Earth’s history.

  Respiration was around for billions of years before multicellularity.

  Life did not get gradually larger as the oxygen level rose, but stayed

  unicellular. Maybe this was because it could not make the move until a

  certain threshold was crossed—a minimum oxygen richness for big life.

  When multicellularity did arrive, however, its entrance was not sub-

  tle. After waiting for so long, it burst onto the scene dramatically. Six

  hundred million years ago, animals materialized, and soon they were

  everywhere, appearing in a multitude of forms. We call this event the

  Cambrian explosion.

  It was as if some repressed creative force in nature was finally set

  free. The evolutionary creation of major animal body types is not some-

  thing that began in the Cambrian and has continued to the present day.

  Rather, these templates seem to have mostly formed all at once. Species

  come and go, riffing endlessly on the grand structural themes that were

  all established at the time of the Cambrian explosion.

  G E T T I N G S M A R T

  Once we became multicellular, entirely new possibilities for organiza-

  tion and specialization opened to us. Legions of cells could now be

  called upon to dedicate their lives to specific structures and tasks.

  Skeletal, circulatory, and digestive systems provided the infrastructure

  for large bodies. Muscles and limbs sprouted for swimming, running,

  climbing, and flying.

  It doesn’t do any good to have such nifty toys if you can’t control

  them, though. A nervous system was needed. The ability to sense the

  environment and respond to it would be a definite plus. From such

  humble needs were born refined senses and mechanisms for sending

  signals throughout the body. Now you’re receiving information and

  coordinating reactions and movements, so you need some kind of cen-

  tral processing site. If you only had a brain.

  Once you’ve got that, then you’ve got the rudiments of a cognitive

  system. You’re on your way now, kid. You’ve got a leg up if you can

  respond to your environment in flexible ways. This creates a pull for

  more complex nervous systems with increasing power to sense, manip-

  ulate, navigate, anticipate, and remember the world.

  Then, 600 million years after the Cambrian explosion, something

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  new happened. Matter woke up in human form. Was it a gradual focus-

  ing or a sharp blink of self-recognition? We don’t remember. I doubt

  we’re fully awake now. Intelligence, consciousness, self-awareness, the

  divine spark of Jah—call it what you will.* We don’t know exactly

  what crucial ingredient was added, or what threshold value was sur-

  passed. One species started talking, building tools, and creating new

  societies, not just out of instinct but through culture, ritual, and design.

  A number of changes happened quickly as our hominid ancestors

  sprinted into the new, big-head niche. We developed opposable thumbs

  for grasping. An upright stance freed those hands to make tools and

  throw spears. Language gave us the ability to communicate complex

  ideas within groups. A rapid increase in brain size, doubling in about a

  million years, facilitated all of the above, but made childbirth difficult

  and dangerous. Evolution responded by pushing birth back earlier in

  development, so that our expanding heads could make it through the

  birth canal. As a result, humans, compared to most other animals, are

  born unformed and helpless. This required prolonged and attentive

  infant care, which increased social cohesion.

  Recall that previous great leaps of evolution involved new associa-

  tions between preexisting simpler organisms. Similarly, the origin of

  human beings is inseparable from the origin of human societies. The

  beginnings of language, the rapid growth in neural capacity, the forma-

  tion of social groups with division of labor and the ability to plan and

  learn collectively—all seem so tightly linked that it may be meaningless

  to ask what caused what. These abilities seem to have bootstrapped one

  another into existence. With language came the advent of a powerful

  new form of heredity. We are cultural animals, and we pass on informa-

  tion through word of mouth and artifacts: artworks, songs, rituals,

  rhythms, stories, and now books, films, and disc drives. Our minds

  expanded beyond our bodies and our thoughts came to survive the

  death of individuals. A new kind of multi-organismic structure—the

  society—was born.

  Less than one hundred thousand years ago a small band of us, possibly

  no more than fifty brave souls, left our native Africa and began spreading

  *I’m not saying that other animals don’t have some degree of it. Some elephants can play the marimba pretty darn well.

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  around the Earth.* These pioneers are your ancestors, unless you are of

  pure African descent, in which case their less restless cousins are your

  ancestors. Perhaps only fifty thousand years ago, we started using syntac-

  tical, symbolic language, which allowed us to communicate abstract con-

  cepts and poetry and planted the seed for the language of mathematics.

  The more we can understand the tangled causal relationships that cat-

  alyzed the jump to human awareness, the more informed will be our spec-

  ulations on the likelihood of similar evolutionary events on other worlds.

  T H E P S Y C H O Z O I C A G E

  However it happened, it is clear that in just a few million years, in

  barely the blink of a cosmic eye, one lineage of primates went through

  an intense metamorphosis, and Earth acquired thought and self-

  awareness. Several scientists and philosophers have recognized this as a

  profound moment of transformation in Earth history. Pierre Teilhard

  de Chardin, the Jesuit paleontologist/philosopher described it in 1955

  as the beginning of a new geological age, the “psychozoic era.” He

  described the web of interacting thoughts, communications, and arti-

  facts rapidly covering the Earth as a new terrestrial sphere, the noo-

  sphere (new-oh-sphere), which emerged out of the biosphere as the bio-

  sphere had emerged out of the rocky lithosphere.

  Although I cannot follow Tielhard all the way to his Christian con-

  clusions, I find his vision of the human place in Cosmic Evolution to be

 
prescient and inspiring. I am with him when he says, “With hominiza-

  tion, in spite of the insignificance of the anatomical leap, we have the

  beginning of a new age. The earth gets a new skin. Better still, it finds

  its soul.”

  Am I giving us too much credit here, going on about the arrival of

  humanity as though we were the second coming of sliced bread? Does

  this view of planetary history place humans at the apex of creation?

  Isn’t this picture of evolution a hopelessly self-serving glorification of

  the human race?

  Not necessarily. Read on, and you will find that I do not see us as the

  apex of evolution. I believe that humans are the resident example of

  something extremely significant on a cosmic scale. We may not even be

  *Some scientists believe, on the basis of DNA studies, that it was less than fifty people.

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  a particularly promising example. But that “something” is essential in

  Cosmic Evolution. Without it, what’s the point? I believe we are part of

  the very beginning, locally, of a phenomenon integral to the conscious

  awakening of the universe. Whether we will be part of later stages

  remains to be seen.

  Conveniently, this realization gives us a new way to be human-

  centered, even though science has robbed us of an Earth-centered cos-

  mos and a purposeful human creation. Are we conflicted, hapless

  humans really the vanguard of a new, conscious phase of Cosmic

  Evolution? Deserve it or not, we are.

  Lest our already dangerously bloated braincases become even more

  swollen with this thought, keep in mind that of the species that ushered

  in the age of multicellular life in the Cambrian explosion, all are long

  gone and forgotten to everyone but curators of paleontology. But multi-

  cellularity lives on. The phenomenon is more important than the

  ephemeral particulars of who was first. Humanity does represent some-

  thing the likes of which Earth has never seen, but the jury is still out on

  our legacy and longevity as a species.

  It seems as though, on principle, some people want to deny any evo-

  lutionary importance to humans. I see this as a reaction to the historical

  tendency to assume that humans were the purpose of creation, the cen-

  ter of the universe and the pinnacle of life. We now know better than to