June 18, 2004 | David F. Coppedge

Stickleback Fish Achieve Stardom in Evolutionary Labs

According to Elizabeth Pennisi in Science June 18,1 the three-spine stickleback is being studied in 100 labs as a model of evolution.  Over the last century, the little fish has been the subject of some 2000 papers, seven textbooks, and a Nobel prize-winning thesis.  Evolutionists have been attracted to this fish because it appears to evolve quickly; outward changes have been observed in short time scales, especially as populations migrated from marine to freshwater environments.  Some studies have suggested “a provocative idea that a little DNA—perhaps just a single gene—can control many traits that affect an organism’s ability to thrive.”  Maybe this fish, easy to cultivate in the lab and found in a variety of natural environments, can provide evolutionists a genetic basis for rapid speciation:

Since the 1930s, the prevailing view has been that evolution moves in a slow shuffle, advancing in small increments, propelled by numerous, minor genetic changes.  But some have challenged this dogma, notably H. Allen Orr, an evolutionary biologist at the University of Rochester in New York.  In 1992, he and his colleagues argued that just a few genes, perhaps even one, could power long-term change.  Such change could rev up speciation.  Lately, the Orr camp seems to be gaining ground, in part because of studies of sticklebacks, says R. Craig Albertson, an evolutionary biologist at the Forsyth Institute in Boston.  He and others are finding that “simple genetic changes can have profound effects. 

On closer inspection, however, the effects do not appear all that profound, and the genetic bases for them appear to be of questionable value for evolutionary theory.  The marine species and the freshwater species supposedly branched apart 22,000 years ago as retreating glaciers trapped some populations in freshwater lakes.  Yet the primary differences involve lower numbers of body plates and shorter spines on the more recently-evolved freshwater populations, as well as changes in the shape of the jaw and some other bones.  From Pennisi’s review, here are the observations that are drawing evolutionists to the study of sticklebacks:

  • Convergence:  “Although they evolved to look very different from their ancestors, they often came to resemble their counterparts who were evolving in a similar way in lakes that are geographically distant….”
  • Interfertile Variety:  “‘These remarkably divergent populations have created a unique resource,’ in part because freshwater and saltwater populations can interbreed.”
  • War and Peace:  The differences appear to be adaptive:

    Oceangoing sticklebacks are built for battle.  Prominent spines stick out behind their lower fins, and their bodies are covered with as many as 35 plates—presumably to fend off predators.  But spines and plates are reduced or missing in most of their freshwater cousins, probably an adaptation to the new habitat.  It pays to lose the bulky armor, says Michael Bell, an evolutionary biologist at the State University of New York, Stony Brook: Lakes may favor lightness because they typically have places to hide, if fish can dart into them fast enough.  Because fresh water lacks the rich calcium reserves of salt water, bony armor could also be too costly to make.  Whatever the cause, “selection against [these traits] must be incredibly strong” to cause such rapid evolution, says Foster.

  • Loss of Information:

    This selective pressure seems to be targeting the same part of the genome in fish at various geographic locations.  In every population researchers have examined, from Japan to California to Iceland, they are finding the same thing: A gene or set of nearby genes is causing the loss of certain parts of the fish’s armor.  “It’s remarkable,” says Postlethwait, that a single gene could exert such a large effect in so many different groups of sticklebacks.  Along with armor, “a whole suite of bony characters is changing,” he says, including jaw shape and bones associated with protecting the gills.  This is not what researchers had expected to find.  But when they tried a breeding experiment, the same pattern emerged: Small DNA segments affected vast areas of bone and armor.

  • Dominance:  “In one experiment, they crossed marine and freshwater fish and found that the resulting offspring all had a complete set of armor and a fully formed pelvis— suggesting that the DNA, or allele, belonging to the marine fish overrode the effects of the allele of the freshwater cousins.”
  • One for All  “Next, the Oregon researchers tested to see if the altered pelvis and lateral plates of the lake fish were controlled by the same genes in each population.  They expected the opposite: that the gene involved in armor loss would be different in the three groups because each had evolved that trait independently.  But their surprising finding was that the alterations were always in the same gene.” 
  • Speed:  “Bell has found that, from an evolutionary perspective, this gene may change at lightning speeds.  In the most recent issue of Evolution, he and his colleagues report on a case in Alaska where plates disappeared in most fish within a decade.”  The results, Pennisi comments, “ suggested that natural selection had taken its toll on the armored fish in just a few years.”
  • Spinelessness:  A similar one-gene effect has been found with the pelvic spines.  Genes in freshwater populations lacking spines were missing a protein known to be active in the formation of limbs in mice.
  • Expression:  The spineless fish still had the gene for spines.  “ The solution … is that a change in the gene’s regulation—and not in the gene itself—caused the lake sticklebacks to lose their spines.  Simply changing the way a gene is regulated in one part of the anatomy or at one point in development ‘is one of the ways to make a [change in a] very powerful development control gene without having detrimental effects,’ says Kingsley.”
  • Ignorance: 

    Researchers have found that other organisms such as birds seem to exhibit the same or similar new traits because of changes in the activity of the same genes, even when the species are unrelated (Science, 19 March, p. 1870).  No one knows exactly why.  It could be that certain genes or bits of regulatory DNA are particularly prone to mutation.  Or perhaps rapid evolutionary responses are channeled into genes that don’t affect development on a broad scale, so as not to short-circuit an organism’s ability to survive.  As a result, “you find the same gene involved more often than you would initially expect,” says Schluter.  He and other stickleback experts are trying to solve this puzzle.

More research is needed, she concludes:

Bell hopes that these studies will lure even more developmental, evolutionary, and genetic biologists to the study of these fish.  Evolution occurs at many levels, involving modifications of DNA sequence, alterations in development, shifts in behavior, changes in community structure, and, ultimately, survivalIt’s important to see how these various levels interact during natural selection.  Adding molecular genetics studies to stickleback science, he predicts, “will allow us to tie up everything in one neat package.”

1Elizabeth Pennisi, “Evolutionary Biology: Changing a Fish’s Bony Armor in the Wink of a Gene,” Science, Vol 304, Issue 5678, 1736, 18 June 2004 [DOI: 10.1126/science.304.5678.1736].

Sometimes we have to provide enough detail to prove we are not making this stuff up.  If we just summarized this story with an opinion like Evolutionists base their belief in macroevolution on oscillatory changes within one species, someone might question that conclusion.  But here it is, mostly in their own words.  You just read it yourself.  We just highlighted their model organism for evolutionary studies, the one they are proud of and excited about.  They are calling all evolutionists to jump on the bandwagon because of the fantastic evidence it provides that humans came from amoebas.  And the evidence is?  They have demonstrated that some fish lost a few spines and armor plates, and got them right back again when they interbred with their marine relatives.  No speciation occurred.  Most of the evolution was due not to a genetic change, but a change in the expression of a gene.  The genes for loss always mutated the same way in widely-distributed populations.  This is not what neo-Darwinism hoped for.  Random mutation was supposed to provide the raw material for novelty and innovation, not the same mutation over and over in the same gene.  Despite all the hoopla, no novel, innovative feature emerged from all this so-called evolution.
    Surely if there were better evidence for evolution than this, it would be showcased by Science magazine.  The hype in the opening paragraphs attracted our attention, because it seemed that now, finally, we were going to get some solid evidence for real evolutionary change.  But look how trivial the results; all the populations are not only still fish, but three-spine stickleback fish.  They are all still interfertile, indicating no speciation occurred.  How is this story much different from what we already know about blind cave fish?  They are adapted to the darkness, because eyes are not of much use in the dark.  Similarly, the lake sticklebacks might be adapted to their habitat (if their just-so story holds up that armor and spines are less helpful when there are more places to hide).  On the other hand, the difference might only be a non-adaptive effect of lower concentrations of calcium, as in nutrient deficiency diseases in humans.  “Whatever the cause,” pre-existing information was either lost or unexpressed in both cases.  No new structure or function was gained.  How can this possibly be of any good news to someone who wants to explain the whole of biology by evolution?
    The article is enthusiastic about how “powerful” selection must have been, yet sprinkled with wiggle words expressing doubt: probably, maybe, might etc.  As usual, the ignorance is profound and more funding is needed, so that the evolutionary storytelling fest can go on and on and on.  But the actual evidence should make it clear that this evolutionary tale makes no more sense than claiming that a new human species is emerging from a population of scurvy sailors deprived of vitamin C.  It doesn’t take much to get an evolutionist excited.  To a prisoner, even the breeze-blown dust dancing on the floor is entertainment.  Maybe it will evolve into a tornado, and from there, a 747 can’t be far behind.

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Categories: Marine Biology

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