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What Does Two Billion Years of “Extreme Evolutionary Stasis” in Bacteria Say About Evolution?

Casey Luskin

J. William Schopf photo I (in UCLA studio).jpg

David Klinghoffer wrote earlier regarding that story making the rounds about deep-sea bacteria that seem not to have changed for some two billion years, yet are being cited as powerful evidence for Darwin’s theory. As David notes, the ever-dutiful LA Times headlines its article, “By not evolving, deep sea microbes may prove Darwin right,” while the Washington Post touts “The mysterious 2 billion-year-old creature that would make Darwin smile.Phys.org goes with a less polemical headline: “Scientists discover organism that hasn’t evolved in more than 2 billion years.”

The organisms are sulfur bacteria, and are said to be a “living fossil” that hasn’t changed in 1.8 to 2.3 billion years. That is according to fossils apparently of the same organisms recently studied by UCLA’s J. William Schopf (pictured above) and his colleagues. One scientist who co-authored the study said, “The microbes we see in the fossils are almost identical to what we see in the ocean now.” The technical paper in Proceedings of the National Academy of Sciences USA calls it “extreme evolutionary stasis.”

The idea is that populations of organisms only change when their environment changes. If the environment doesn’t change then there’s no reason for the population to evolve. And how do we know their environment didn’t change? Because the bacteria didn’t evolve. And why didn’t they evolve? Because their environment didn’t change. Once again, Darwinism predicts whatever it finds, and finds whatever it predicts. Here’s how the PNAS paper puts it:

The apparent 2-billion-year-long stasis of such sulfur-cycling ecosystems is consistent with the null hypothesis required of Darwinian evolution — if there is no change in the physical-biological environment of a well-adapted ecosystem, its biotic components should similarly remain unchanged

Of course it’s quite reasonable from an evolutionary perspective to say that if the environment isn’t changing then populations of organisms in that environment probably won’t change much either. That’s why when I wrote about living fossils last year at ENV (“What Do ‘Living Fossils’ Mean for Evolution?“), I explained that they really don’t have much to say for or against Darwinian theory:

While some Darwin-critics make a big deal about so-called “living fossils,” I’ve never discussed them much because it’s never been entirely clear to me what they show, whether for or against neo-Darwinian evolution. Living fossils are of course organisms that have not changed at all over long periods of time. In some cases, such as the horseshoe crab, the coelacanth, or the ginkgo tree, these species seem to have remained virtually the same for hundreds of millions of years. … But when Darwin-advocates cite living fossils as powerful evidence FOR Darwinian evolution, it’s ironic because they’re saying: Everything proves evolution– even the absence of evolution! Such talk would be funny if it weren’t being offered in dead seriousness. It’s also a reminder of the unhealthy state of evolutionary biology. Scientists feel pressured to pretend that anything and everything — including species that show no evidence of change at all — confirms the Darwinian thesis, thus demonstrating their neo-Darwinian bona fides even while discussing an awkward topic like living fossils.

That’s exactly how these two-billion-year-old bacteria fossils are being offered by the newsmedia now — as some kind of compelling evidence for Darwinian theory. In fact, the current news articles on the subject exhibit something of a nervous fear that the public will view these “living fossils” as evidence against evolution. Thus, this current flurry of news coverage is rhetorically framed, and timed just as the paper was published, to defeat that argument. Here’s what they say:

  • Washington Post: “But the fact these particular organisms successfully avoided evolving for billions of years doesn’t disprove the theory of evolution — quite the opposite. Darwin’s theory states that species evolve through natural selection in response to environmental changes — increased threats from predators, new competition from other animals, changes in access to water or air. But the inverse is also true: If there is no change in the environment of a balanced ecosystem, the organisms that constitute it should remain similarly unchanged — a principle dubbed evolution’s ‘null hypothesis.'”
  • LA Times: “Researchers say these microscopic organisms are an example of ‘extreme evolutionary stasis’ and represent the greatest lack of evolution ever seen. They may also, paradoxically, prove that Darwin’s theory of evolution is true. ‘If evolution is a product of changes in the physical and biological environment, and there are no changes in the physical and biological environment, then there will be no evolution,’ said J. William Schopf, a paleobiologist at UCLA.”
  • Phys.org: “An international team of scientists has discovered the greatest absence of evolution ever reported — a type of deep-sea microorganism that appears not to have evolved over more than 2 billion years. But the researchers say that the organisms’ lack of evolution actually supports Charles Darwin’s theory of evolution.”

It’s as if the articles were coordinated to preemptively rebut the crazy idea that a lack of evolution might suggest a lack of evolution. No, I’m not suggesting a conspiracy. The original press release from UCLA cast the story in these terms and journalists, who may be aware of scientific objections to Darwin’s theory, and are ever-eager to defend it, have been retelling the story in an instinctive defensive mode.

The one evolutionary idea that these bacteria might demonstrate is purifying selection — the power of natural selection to prevent organisms from changing when their current state is well-suited for survival, and evolutionary change might even diminish chances of survival. If so, however, such living fossils still provide no evidence for some of the grander claims of neo-Darwinism — notably, that random mutation and natural selection can change one type of organism into a fundamentally new type of organism. This type of change would require what’s called “positive selection,” and it receives no support from this finding.

In other words, the organisms reported now in PNAS confirm only a trivial and uncontroversial part of Darwinism. The grander parts, what people really mean whey they talk about Darwin’s theory, remain unestablished, just as before.

Image credit: UCLA Center for the Study of Evolution and the Origin of Life.

Casey Luskin

Associate Director, Center for Science and Culture
Casey Luskin is a geologist and an attorney with graduate degrees in science and law, giving him expertise in both the scientific and legal dimensions of the debate over evolution. He earned his PhD in Geology from the University of Johannesburg, and BS and MS degrees in Earth Sciences from the University of California, San Diego, where he studied evolution extensively at both the graduate and undergraduate levels. His law degree is from the University of San Diego, where he focused his studies on First Amendment law, education law, and environmental law.