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The Persistence of Saltationism

One of Charles Darwin’s predictions was that evolution occurs gradually via variations within populations. His friend Thomas H. Huxley was concerned that Darwin had assumed “an unnecessary difficulty in adopting Natura non facit saltum [nature does not make leaps] so unreservedly.” But Darwin’s theory would have been much less compelling without it. Imagine if evolution had included the caveat that saltations—rapid leaps—can occur by unknown mechanisms such that new fossil species can appear fully formed. This would have destroyed Darwin’s premise that species evolve by natural processes and we wouldn’t be talking about him today.  Yes the fossil record suggested that nature does take jumps, but it was safer for Darwin to question the data than to admit them into his theory.  Read more

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4 Responses to The Persistence of Saltationism

  1. So what is the difference between saltation and punctuated equilibrium? My understanding is that saltation just means that new and complex forms just appear suddenly. Is there a proposed mechanism?

  2. Imagine if evolution had included the caveat that saltations—rapid leaps—can occur by unknown mechanisms such that new fossil species can appear fully formed. This would have destroyed Darwin’s premise that species evolve by natural processes and we wouldn’t be talking about him today.

    Nonsense, there is no reason why both gradual and saltational changes couldn’t exist alongside each other, just like selection and genetic drift.

    And it’s not as if saltation is thought to be commonplace. To quote from the summary of the article you cited:

    In my view, gradual changes represent the usual mode of evolution, but are unlikely to be able to explain all key innovations and changes in body plans. Saltational changes involving hopeful monsters are probably very exceptional events, but since they have the potential to establish profound novelties sometimes facilitating adaptive radiations, they are of quite some importance, even if they would occur in any evolutionary lineage less than once in a million years.

  3. Collin @ 1

    So what is the difference between saltation and punctuated equilibrium?

    Saltation refers to major changes, possibly even the formation of a new species, in just one generation.

    Punctuated equilibria is Gould and Eldredge’s theory that the rate of gradual evolutionary change, as revealed in the fossil record, has changed, sometimes quite drastically, from time to time.

  4. “Imagine if evolution had included the caveat that saltations—rapid leaps—can occur by unknown mechanisms such that new fossil species can appear fully formed.”

    Ah, it’s statements like these that just keep me coming back, I gotta say.

    Imagine if relativity had included the caveat that accelerating objects can exceed the speed of light if they wish for it hard enough?

    Imagine if germ theory had included the caveat that sometimes microbes grow hundreds of feet tall and terrify cities with their radioactive breath?

    Look, the fossil record is not one of saltation merely by virtue of large gaps. That’s insane. Continuing from that logic, each saltated organism must have lived for millions of years before reproducing another salatated organism. Otherwise, we have to make the assumption that other organisms existed between the two, and this is unwarranted because those organisms’ fossils have not been found.

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