Invent Animals: Just Add Phosphorus

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Posted on June 11, 2007 in Dumb Ideas, Fossils

Phosphate does a body good,” announced Leslie Mullen in an article for Astrobiology Magazine, a NASA website.  So good, in fact, it builds whole new body plans.  Her story suggests that the Cambrian explosion was due to a rise in phosphate in the oceans.
    In the Cambrian explosion, virtually all the animal phyla appeared in the geological blink of an eye.  Without blinking her eye, Mullen asked, “The rock record shows that phosphorus, once scarce, became abundant around the same time as the Cambrian explosion.  Could phosphorus be the key to unlocking the mystery behind the Ediacaran extinction and the sudden emergence of animal life on Earth?”
    The invention of complex body plans found in Cambrian fossils was attributed to an unknown process named emergence:

  • Was the extinction of one kind of life related to the emergence of another?  If so, what role did the environment play in tipping the scales?
  • Could phosphorus be the key to unlocking the mystery behind the Ediacaran extinction and the sudden emergence of animal life on Earth?
  • The emergence of hard parts in animals by phosphate deposition could account for the “explosion” of fossils in the Cambrian rock record, since hard parts are better preserved over long time scales than soft body parts.

Mullen’s article focused on the opinion of Jim Elser (Arizona State), who investigated Cambrian rocks for their phosphate content.  But she was careful to air the views of a skeptic: Bruce Runnegar of UCLA.  He thinks the secret ingredient was oxygen.  “I would put more money on oxygen rather than phosphate as an intrinsic trigger of the Cambrian explosion,” he said Runnegar.  “Phosphate may have been a follower rather than a leader.”
    Controversy may continue far into the future, Mullen acknowledged.  How do you solve a puzzle with an infinite number of pieces?

The cause of the Cambrian explosion and the mass extinction that preceded it is made complicated by the seemingly infinite pieces that make up the whole puzzle.  Figuring out how the different environmental elements may have interacted is difficult, in part, because the world back then was such a different place than the one we now experience.  Whether phosphate is a key piece in that puzzle, merely a contributing factor, or simply a side effect of other events remains a mystery.  What is certain is that the development of such biomineralization made nature the bloody battlefield of tooth and claw versus protective body armor that continues to this day.

For assuming that environmental causes alone produced the eyes of trilobites, the vertebrae of fish, and all the other organs of dozens of phyla; for attributing this complexity to the addition of certain atoms; and for regurgitating the Malthusian (06/05/2007) iconic imagery of red teeth and bloody claws; Mullen wins Stupid Evolution Quote of the Week.

NASA’s Astrobiology program: your tax dollars berserk.

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