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Multicellular fossils may be world's oldest

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  • robert-blau@webtv.net
    ! . . . Multicellular fossils may be world s oldest Fossils found in Gabon suggest complex organisms lived as far back as 2.1 billion years ago,paleontologists
    Message 1 of 1 , Jul 2, 2010
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      ! . . .

      Multicellular fossils may be world's oldest

      Fossils found in Gabon suggest
      complex organisms lived as far back as 2.1 billion years
      ago,paleontologists say.
      [image: Gabonese Fossils]

      Paleontologists used X-ray tomography to virtually reconstruct the outer
      form, left, and inner structure of the fossil specimens.
      - Related
      - [image: Map: Oldest known multicellular fossil
      found]<http://www.latimes.com/news/science/la-sci-fossil.eps-20100701,0,6451264.graphic>
      Map:
      Oldest known multicellular fossil
      found<http://www.latimes.com/news/science/la-sci-fossil.eps-20100701,0,6451264.graphic>

      An international team of paleontologists has uncovered the earliest
      known
      multicellular fossils, pushing back the fossil record for such life
      forms to
      2.1 billion years ago and suggesting that they lived 200 million years
      earlier than scientists had thought.

      Since most fossils in that period were microscopic and single-celled,
      finding fossils that stretched as long as 4.75 inches was "like ordering
      an
      hors d'oeuvre and some gigantic thick-crust pizza turning up," said
      Philip
      Donoghue, a paleontologist at the University of Bristol, who co-wrote a
      commentary on the finding. The report detailing the fossils, along with
      the
      commentary, was published online Wednesday in the journal
      Nature<http://www.nature.com/nature/index.html>
      .
      The organisms, which don't resemble modern-day living things, existed
      when
      Earth's atmosphere would have been uninhabitable for today's plants and
      animals.

      Their fossils provide "the first record of that fundamental threshold in
      organismal complexity being surpassed," Donoghue said. "To put it into
      context, the godfather of evolutionary biology, John Maynard Smith,
      identified eight major events in evolutionary history; achieving
      multicellularity was one of these."

      "I was astonished.... It's not the sort of thing you expect to see in
      rocks
      of that age," Donoghue said.
      Paleontologist Abderrazak El Albani, the report's lead author, said the
      macroscopic fossils, which are visible to the naked eye, turned up at a
      point during the Paleoproterozoic era when life was thought to exist on
      a purely microbial level.

      Learning about how and under what conditions that turning point was
      reached
      — it has happened at least 17 times in lineages that are still living,
      Donoghue said — could reveal much about how life developed.

      The finding also dovetails with theories describing what Earth's
      environment
      must have been like at the time, illuminating how the changing
      atmosphere
      may have played a role in the development of life.

      About 2.4 billion years ago, scientists say, oxygen began to build up
      dramatically in the environment. Though the element would have amounted
      to only a fraction of current levels, it may have been sufficient to
      allow some creatures to begin developing into multicellular organisms,
      the researchers theorize.

      Given that the record for such ancient forms of multicellular life is
      spotty
      at best, Donoghue said, "we're certainly hungry for fossils in those
      intervals of our history."

      Study coauthor Stefan Bengtson, a paleozoologist with the Swedish Museum
      of Natural History, pointed out that multicellularity was a key
      development in
      life on Earth because "once you start building things with smaller
      things,
      you can start building new structures, like a Lego game."

      But there's still a long evolutionary road between these creatures and
      those
      whose genetics were complex enough to develop different tissues and
      organs
      within a single body, Bengtson said.
      El Albani, of the University of Poitiers in France, said his team had
      been
      looking to study the sediments at the black shale formations in Gabon
      when
      they came across the fossils.

      They weren't much to look at: lumpy and doughy-looking, though hard, of
      course. But a scan using X-ray tomography revealed complex organization
      and folding.

      "It's spectacular.... It's really something," El Albani said of the
      structure.

      The team also had to prove that the structures had been organic in
      nature.
      The fossils were found to contain tiny grains of pyrite, or fool's gold.
      Such grains would have been created by sulfur-breathing bacteria
      munching
      away at organic matter, in this case the soon-to-be fossils' dead
      tissues,
      the scientists said.

      El Albani said the next step would be to examine the fossils to learn
      more
      about how they lived and what their surroundings were like.

      "I want to understand if this organism is moving or not; I want to
      understand the paleological ecosystem," he said.
      amina.khan@...

      Source<http://www.latimes.com/news/science/la-sci-fossil-20100701,0,2900726.story>
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