‘Big Bang’ of Species May Be Explained by Continental Shift

Nov 7, 2014

Credit: Ian Dalziel

By Kelly Dickerson

A sudden explosion of new life-forms hundreds of millions of years ago may have been triggered by a major tectonic shift, new research shows.

About 530 million years ago, the Cambrian explosion brought a surge in new species to Earth, including most modern animal groups. Recent studies suggest that, during the Cambrian explosion, life evolved about five times faster than it’s evolving today. The sudden increase in species is sometimes referred to as “Darwin’s dilemma” because, at face value, it seems to contradict Charles Darwin’s theory of gradual evolution.

Scientists are still unsure what caused the number of species to skyrocket in such a short period of time, but Ian Dalziel, a research professor at the University of Texas Institute for Geophysics, thinks part of the answer may lie in how the continents shifted.

Dalziel thinks the ancient continent Laurentia (present-day North America) remained attached to the fused supercontinent Gondwana longer than current reconstruction models suggest. Some current models suggest Laurentia had already broken off before the Cambrian period. Instead, Dalziel thinks a deep ocean developed between Laurentia and Gondwana during the early Cambrian period and that the tectonic shift and resulting ocean likely caused sea levels to rise.


 

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13 comments on “‘Big Bang’ of Species May Be Explained by Continental Shift

  • If memory serves…

    Has not the ‘Cambrian Explosion’ itself been partially exploded? Stephen Jay-Gould’s phrase concerned not speciation but the development of new Phylla in the Burgess Shales. RD has pointed out the fallacy of the characterisation used there.

    Recent work has reached back further and suggests that poor detection and preservation of material is responsible for a lack of data for the gradual divergence of taxa in the Pre-Cambrian.

    The displaced water created new shallow-water environments that opened
    up new niches for new species to fill. The shifting continents also
    likely caused an upwelling of deep-ocean water that brought an influx
    of nutrients into shallow waters that allowed new life-forms to
    flourish, Dalziel said.

    Do I hear the squeek of a shoehorn?



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  • Geoff 21 Nov 8, 2014 at 9:43 am

    Has not the ‘Cambrian Explosion’ itself been partially exploded? Stephen Jay-Gould’s phrase concerned not speciation but the development of new Phylla in the Burgess Shales. RD has pointed out the fallacy of the characterisation used there.

    If something evolves in one million years when a comparable evolution elsewhere with less diverse selection pressure, takes 5 million years, this is only “fast” in terms of geological time.

    There is nothing about “gradual evolution” which says it only has one speed in bottom gear!



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  • D’accord.

    As you say ‘radiative speciation’ is not denied by theory and can accelerate the differentiation of taxa; E.O.Wilson treats of the subject well in ‘The Diversity of Life’.



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  • 5
    Light Wave says:

    Species evolve because there are new specialised niches for them to differentiate from existing species… in the long term though, the speed of evolving species may well slow down as a critical maximum of available niches is reached, tectonic shifts occur all the time its hardly a species bloom -producing event….but tectonic plates colliding that have never met would change the dynamics of the species that live on both plates and many new ones may evolve quickly initially but balance out as food source and habitat niches are filled….. of course the mass extinction of most species just before the explosion of new species – really helped clear the decks for all the new species that could now fill the empty niche voids….



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  • 7
    Otangelo says:

    Even if the arise of oxygen was due to tectonic shift, it does not explain the sudden arise complex life forms, like trilobite eyes. Where did the information to make advanced organisms come from ? And neither does it explain the nitrogen cycle, which is interdependent.

    http://elshamah.heavenforum.org/t1562-the-nitrogen-cicle-irreducible-interdependence-and-the-origin-of-life?highlight=nitrogen

    And neither complex capacities of cyanobacterias, which were able of extremy complex, interdependent and irredudibly complex mechanisms like photosynthesis, and nitrogenase.



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  • There are lots of routes for getting nitrogen into biotic circulation. Formaldehyde can generate sugars and sugars can release fixed (chemically active) nitrogen from nitrites as ammonia. Several other paths are available. Google is your friend and include the term pre-biotic. Choose scientific sites if you want to find actual science though.



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  • Otangelo Dec 7, 2014 at 6:55 am

    Even if the arise of oxygen was due to tectonic shift, it does not explain the sudden arise complex life forms, like trilobite eyes. Where did the information to make advanced organisms come from ? And neither does it explain the nitrogen cycle, which is interdependent.

    Tectonic shifts are about changes in climate, and the opening and closing of migration routes. These merely provide opportunities for evolutionary changes in new habitat niches. Once species are geographically separated and natural selection is picking the more competitive survivors in the new habitats, the ancestral form will branch into separate species.

    A shift like this one would produce a massive increase in fertile coastal areas.

    it does not explain the sudden arise complex life forms, like trilobite eyes.

    Eyes have independently evolved many times in marine organisms such as shellfish, spiders, insects, vertebrates. They gradually evolve from mere light sensitive spots which can detect shadows, to eyes like pin-hole cmeras and some with various material forming lenses. Many different levels of complexity are shown in modern animals, where the ability to see or detect shadows of predators, aids survival.



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  • @Alan

    A new book by Andreas Wagner has some interesting new expansions on the idea of probabilities of random mutations hitting useful outcomes for our compounded selection pressures. By investigating, with the use of simulations, the actual potential utility within the mutation space, the probabilities of hitting the jackpot go up considerably. Opsin in retinas could be a myriad of other actinic chemicals.

    You can still catch him on last weeks “Start the Week”.



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  • phil rimmer Dec 7, 2014 at 8:05 am

    @Alan

    A new book by Andreas Wagner has some interesting new expansions on the idea of probabilities of random mutations hitting useful outcomes for our compounded selection pressures.

    When it comes to probabilities, the sheer numbers of single celled organisms in an ocean of water, over millions/billions of years, stacks the odds quite heavily.



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  • Otangelo Dec 7, 2014 at 6:55 am

    @link In short :

    The short argument :

    Without cyanobacteria – not enough fixed nitrogen is available.

    Very short argument. – Anaerobic single celled organisms existed by chemosynthesis, for millions of years before photosynthesising Cyanobacteria or nitrogen cycles evolved.

    The ATP is needed to fuel the activity of nitrogenase, the enzymatic complex capable to fix atmospheric N2, which is irreversibly inhibited in the presence of oxygen (Bergman et al., 1997). Tomitani et al. (2006) suggested, on the basis of genetic distances and fossil calibrations, an age ranging from 2450 to 2100 million years ago (MYA) for heterocystous cyanobacteria, which may predate the rise of atmospheric oxygen at about 2300 MYA.
    http://www.nature.com/ismej/journal/v4/n6/full/ismej20102a.html



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