Loading ...
Sorry, an error occurred while loading the content.

Fwd = Alien Intelligence Depends on Time Needed to Grow Brains

Expand Messages
  • Frits Westra
    Forwarded by: fwestra@hetnet.nl (Frits Westra) URL: http://www.space.com/scienceastronomy/alien_intelligence_021202.html Original Date: Wed, 4 Dec 2002
    Message 1 of 1 , Dec 4, 2002
      Forwarded by: fwestra@... (Frits Westra)
      URL: http://www.space.com/scienceastronomy/alien_intelligence_021202.html
      Original Date: Wed, 4 Dec 2002 02:08:07 +0100 (CET)

      ========================== Forwarded message begins ======================

      Alien Intelligence Depends on Time Needed to Grow Brains

      By Leslie Mullen
      Astrobiology Magazine
      posted: 09:15 am ET
      02 December 2002

      Spock: To hunt a species to extinction is not logical.

      Gillian: Whoever said the human race was logical?

      Star Trek, The Voyage Home

      We expect aliens to be a whole lot smarter than us. Not only will they
      possess the wisdom of the ages, but they will travel at warp speed,
      have the ability to transform (or destroy) entire planets, and their
      civilizations will span across galaxies.

      Until we find alien life, however, we can only guess at how many
      intelligent civilizations may be out there. Frank Drake made a stab at
      guessing the number in 1961, when he formulated the "Drake Equation".

      According to this equation, there could be a million intelligent
      civilizations in the Milky Way galaxy, and probably billions of such
      civilizations throughout the universe.

      The Drake Equation is based, in part, on an estimate of the number of
      planets in the galaxy that might harbor life. Such planets would have
      to exist in "habitable zones" -- those regions around stars that would
      best support life as we know it. These planets would be the most
      likely places where life capable of achieving intelligence is fostered
      and sustained.

      To understand how intelligence develops, we have only one example to
      study: the development of human intelligence on Earth. The first life
      on our planet probably arose about 3.8 billion years ago, less than a
      billion years after the Earth itself formed.

      But multi-cellular life didn't appear until nearly 3 billion years
      after that, and the first animal life didn't form until the Cambrian
      Explosion 600 million years ago. Intelligent life -- which we broadly
      define as human civilization -- didn't develop until a few tens of
      thousands of years ago. Christopher McKay, a planetary scientist with
      the NASA Ames Research Center, has defined intelligence as the ability
      to build a radio telescope. If we go by McKay's definition, then truly
      intelligent life on Earth didn't show up until the twentieth century.

      Since intelligent life took a long time to develop on Earth, some
      believe it will take just as long on other worlds.

      The paleontologist Peter Ward and the astronomer Donald Brownlee
      expressed this belief in their book, "Rare Earth: Why Complex Life is
      Uncommon in the Universe." Intelligent life on Earth, they say, is due
      to a long chain of events that greatly relied on happenstance. The
      odds of such a chain of events occurring on other worlds seem to be
      impossible. Thus, as the title of their book indicates, they believe
      that simple, microbial life may be common in the universe, but complex
      life will be rare. They certainly don't expect to find very many
      advanced alien civilizations out there.

      Other scientists disagree with this conclusion. They suggest that
      animal life -- or something resembling it -- may have developed more
      rapidly on other worlds. One proponent of this theory is McKay, who
      wrote the essay, "Time for Intelligence on Other Planets," in order to
      determine the shortest possible time it would take for intelligence to
      develop after the origin of life.

      Crunching the numbers

      Although the traditional view of evolution is as a constant push
      toward greater complexity, the fossil record on Earth shows instead
      that there were periods of rapid changes followed by long periods
      where nothing much happened at all. McKay says such a drawn-out style
      of evolution need not be universal. By removing what he calls
      evolution's "spurious" time periods, he says that intelligent life
      could take as little as 100 million years to develop.

      "Nothing in our understanding of evolution suggests that these periods
      of stasis are required," says McKay. "We believe they represent mere
      historical happenstance."

      Another limiting factor for evolution on Earth was a lack of oxygen.
      The early Earth had very little free oxygen until cyanobacteria and
      other photosynthetic life forms began producing it about 2 billion
      years ago. Oxygen may be the key to tissue multi-cellularity, and thus
      the formation of large, multi-celled organisms capable of developing a
      brain. The build-up of oxygen also led to the development of an ozone
      layer, shielding life on Earth from the Sun's harmful UV rays.

      But this need not be the case on other worlds. Perhaps some planets
      begin with substantial amounts of atmospheric oxygen. Slower tectonic
      activity would make more oxygen available, as would a less iron-rich
      geography. A planet with early access to oxygen might see life, and
      intelligence, evolve much faster than on Earth.

      Other factors affecting Earth's evolution were cataclysmic events such
      as asteroid impacts. Such events would kill off complex life, but
      these events could also clear the way for the development of more
      advanced forms of intelligence. The creatures with superior brains may
      have been better able to save themselves from the sudden changes in
      their environment caused by these events.

      Many of the factors that went into the development of life on Earth
      remain a puzzle to us, so there may be many other characteristics of a
      planet, or even a solar system, that affect the development of
      intelligence. For instance, some scientists have noted that
      intelligence did not arise on Earth until the Sun hit middle age.
      Perhaps, they suggest, intelligence cannot evolve until the planet's
      star reaches a certain stage in its own evolution.

      Chris McKay, however, says he has not heard a compelling argument as
      to why human level intelligence needed the Sun to be middle aged.

      "I would say that the build-up of oxygen is the only good
      environmental requirement," says McKay.

      Why only one?

      The Earth's fossil record indicates that, despite periods of stasis or
      of setbacks like asteroid impacts, most organisms evolve toward
      greater complexity. Some of Earth's life forms have gone extinct,
      while others became cornered in evolutionary dead ends. But as a
      whole, evolution has moved toward increasing the complexity of the
      central nervous system, culminating in the development of the brain.
      (The "brain" as an organ within the skull did not develop until the
      emergence of the first vertebrate animal.)

      Since evolution seems aimed towards the development of intelligence, a
      planet should be able to evolve not just one, but many intelligent
      species over time. Yet on Earth, humans were the only species who
      developed "radio telescope-building" intelligence.

      "It might be argued that among mammals, humans developed intelligence
      first and are thereby effectively precluding the development of
      intelligence in any other species," says McKay. "It follows from this
      argument that intelligence evolves once and only once on a planet,
      because once evolved it changes the rules of the interaction between
      species and effectively dominates the planet from then on."

      Human intelligence may never have developed if the dinosaurs had not
      gone extinct. During the age of the dinosaurs, our ancestors were
      small, rodent-like creatures scavenging for food in the low grass.
      Perhaps we had to wait for the dinosaurs to disappear before we could
      evolve beyond a certain point. However, says McKay, this theory still
      does not explain why the dinosaurs didn't become the Earth's first
      telescope-builders. They dominated the planet for over 150 million
      years, occupying all the niches mammals currently occupy.

      "That is more than twice the time between the end of the Cretaceous
      and the construction of the first radio telescope," says McKay. "One
      might speculate that perhaps Stenonychosaurus (also known as Troodon)
      or her progeny did build radio telescopes but their civilization was
      destroyed by some internal or external catastrophe. Perhaps the
      lifetime of their civilization was so short, compared to the
      resolution of the geologic record, that it is simply lost without
      trace in the depths of time. It is difficult to say what evidence
      would survive of human civilization - if it was terminated now - after
      65 million years of tectonic activity, erosion, and sea level change."

      Since it seems that intelligence only evolved once on Earth, despite
      other opportunities to do so, perhaps not many forms of intelligence
      could evolve on other planets. McKay says that, considering the
      Earth's evolutionary history, the odds for developing intelligence
      elsewhere may be less than one in three (65/215). Still, given the
      potential number of habitable planets in our Galaxy alone, that could
      mean there are many millions of intelligent species out there.

      "The odds I computed are just a rough upper limit based on the history
      of Earth as we now know it," says McKay. "For us to be the ONLY
      intelligent radio builders in the galaxy, the odds would have much
      lower -- about 1 in million."

      Despite all the rationale behind one viewpoint or another, the
      question of how many intelligent civilizations are out there can only
      be answered if we discover alien life. NASA is planning to launch the
      Terrestrial Planet Finder in 2012. This satellite will operate for 6
      years, searching for Earth-sized planets around distant stars.

      In the meantime, scientists with the Search for Extra Terrestrial
      Intelligence (SETI) continue to explore the electromagnetic spectrum
      for alien transmissions. The SETI Institute recently published SETI
      2020, a book detailing the focus of SETI strategies between now and
      the year 2020.

      This story is presented in cooperation with Astrobiology Magazine,
      a web-based publication sponsored by the NASA astrobiology
      program. http://www.astrobiology.arc.nasa.gov/

      © 2002 SPACE.com, Inc. ALL RIGHTS RESERVED.

      ========================== Forwarded message ends ========================
    Your message has been successfully submitted and would be delivered to recipients shortly.