July 6, 2009 | David F. Coppedge

Evolution of Foraminifera Questioned

A long, long time ago, primitive sea creatures called foraminifera lived on the ocean bottom.  One day, some of them invaded a new ecological niche: the ocean surface.  There, they became part of the plankton zoo.  When the catastrophe that wiped out the dinosaurs occurred, most of the surface foraminifera died.  But they recovered in later epochs, always living near the surface.  That evolutionary story has been called into question by the discovery of a surface (pelagic) dweller that is the same species as an ocean-bottom (benthic) dweller.
    Foraminifera, sometimes called forams for short, can be thought of as amoeba-like organisms inhabiting perforated shells.  Most are very small – about 1mm – but some as long as 19mm in diameter are known.  Their shells of calcium carbonate can be very elaborately decorated.  Forams make up a large part of the ocean’s plankton.
    Evolutionists have portrayed forams evolving first on the ocean floor.  Some became buoyant and colonized the surface.  That was the picture till now.  Writing in PNAS,1 Darling et al said, “Evolution of planktic organisms from benthic ancestors is commonly thought to represent unidirectional expansion into new ecological domains, possibly only once per clade.”  They also noted that “The planktic foraminiferal evolutionary tree is under considerable debate.
    Then they announced their bombshell discovery: “We present surprising but conclusive genetic evidence that the Recent biserial planktic Streptochilus globigerus belongs to the same biological species as the benthic Bolivina variabilis, and geochemical evidence that this ecologically flexible species actively grows within the open-ocean surface waters, thus occupying both planktic and benthic domains.”  OK, so what?  “We argue that the existence of such forms must be considered in resolving foraminiferal phylogeny,” or evolution.  Time to rewrite the textbooks again.
    The authors thought that “The ability to survive in both planktic and benthic habitats should be seen as an extraordinary ecological adaptation for long-term survival.”  Evolutionists seem not to have taken this ability into account.  The same species can be tychopelagic, or able to live on the surface and on the bottom.  Here’s their conclusion:

The Cenozoic planktic foraminiferal phylogeny of microperforates, the group containing biserial and triserial forms, has generally presented taxonomists with problems.  Many of these genera and species show discontinuous stratigraphic records, making ancestor�descendant patterns difficult to reconstruct.  This could be the result of a lack of observation of the small forms, in a size fraction that commonly is not included in study.  In our view, however, such ancestor�descendant relations simply do not exist.  This is supported by recent evidence that the living triserial planktic foraminifer Gallitellia vivans had a Miocene benthic ancestor and thus did not evolve from the Cretaceous�Paleocene triserial Guembelitria cretaceaAppearances of biserial and triserial planktic forms in the geological record should therefore not be considered as necessarily discrete punctuated evolutionary events but as a series of excursions of expatriated tychopelagic microperforates into the planktic domain.

1.  Darwing et al, “Surviving mass extinction by bridging the benthic/planktic divide,” Proceedings of the National Academy of Sciences USA, published online July 2, 2009, doi: 10.1073/pnas.0902827106.

Let’s translate that last clause into plain English.  Once upon a time, some foraminifera on the ocean bottom were being persecuted.  The ruling oligarchy excommunicated them.  Forlorn and forsaken, these expatriates took an excursion.  They floated up to the surface to look for a new life in the Kingdom of Plankton, where the sun always shines and freedom to evolve is a constitutional right.
    So is this paper a victory of gradualism over punctuated equilibria?  No; it’s the latest in the game of hot potatoes.  Earlier evolutionists believed in the prevailing just-so story: that the migration to the surface took place long ago, one time.  The benthic and pelagic groups then lost contact with one another and went on separate evolutionary paths.  But lo, this plot made it hard to arrange the fossil groups into ancestor-descendant relationships.  So now, this team has discovered that some of these creatures can actually inhabit two very different environments at the same time.  That not only falsifies the foundational belief that the earlier evolutionists had about the evolutionary history of foraminifera (including the myths about their extinctions and radiations), it also scrambles the fossil record.  Fossil hunters can no longer assume that benthic and pelagic forms have distinguishable phylogenies.
    The problem density thus remains the same, but the storytelling density increases.  Now we get to hear tales about expatriated foraminifera taking excursions into evolutionary frontiers, where their craftsmen invent extraordinary ecological adaptations for long-term survival, literally out of the blue.  Why not?  In the magic land of Darwinia where the only rule is the Stuff Happens Law, facts are the servants of the wizards.

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Categories: Marine Biology

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