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Researchers: Evolution is not “survival of the fittest”

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At least not in their study of laboratory yeast. From ScienceDaily:

According to the existing theory, the “fittest” DNA would be that which showed up most frequently in subsequent generations. However, the scientists observed “fluctuations” that the theories could not account for.

“Mutations and genotypes that seem to have fallen behind can leapfrog and dominate,” said Cvijović.

What that means, she says, will be the subject of future research. However, it implies that evolution is, indeed, even more complex than previously thought.

“Our experiment suggests there may be a wide range of a large number of strongly beneficial mutations,” she said. “And their benefits are both very strong and very different from one another.” Paper. (paywall) – Alex N. Nguyen Ba, Ivana Cvijović, José I. Rojas Echenique, Katherine R. Lawrence, Artur Rego-Costa, Xianan Liu, Sasha F. Levy, Michael M. Desai. High-resolution lineage tracking reveals travelling wave of adaptation in laboratory yeast. Nature, 2019; DOI: 10.1038/s41586-019-1749-3 More.

From the Abstract: “We show that clonal competition creates a dynamical ‘rich-get-richer’ effect: fitness advantages that are acquired early in evolution drive clonal expansions, which increase the chances of acquiring future mutations. However, less-fit lineages also routinely leapfrog over strains of higher fitness. Our results demonstrate that this combination of factors, which is not accounted for in existing models of evolutionary dynamics, is critical in determining the rate, predictability and molecular basis of adaptation.”

If Darwinism mattered the way it used to, this would be heresy.

See also: Natural selection: Could it be the single greatest idea ever invented?

9 Replies to “Researchers: Evolution is not “survival of the fittest”

  1. 1
    vmahuna says:

    OK, but ya gotta understand that BY DEFINITION, WHATEVER survives long enough to breed IS “the Fittest”, circular argument-wise,

  2. 2
    polistra says:

    If “less-fit lineages leapfrog”, it means they’re more-fit. The researchers don’t understand what Darwin meant, and don’t understand the plain tautology. There’s nothing contradictory or ironic. The only problem is that the researchers are using their own prejudices and theories to decide who’s fit. Instead of deciding in advance who’s fit, they should look at the survivors and figure out what makes them fit in this particular situation.

  3. 3
    AaronS1978 says:

    OK, but ya gotta understand that BY DEFINITION, WHATEVER survives long enough to breed IS “the Fittest”, circular argument-wise

    In another post this is exactly what I’m arguing I couldn’t agree with you more

  4. 4
    ET says:

    Actually, according to evolutionary biology, the fittest are those with the qualities* that allowed them to survive. Those who survive by mere chance do not count.

    *However what those qualities are is anyone’s guess as they are contingent

  5. 5
    DonaldM says:

    Its even worse. After all, what exactly is the mechanism for survival of the fittest? Supposedly its natural selection. But, NS isn’t really a mechanism at all. At best it’s little more than a descriptive phrase to describe an observation after the fact. What are the most fit? Those that NS allows to survive. And what does NS select for? The most fit. And round and round we go!

  6. 6
    ET says:

    From “What Evolution Is”, by Ernst Mayr (one of the architects of the modern synthesis):

    Actually, survival is not a property of the organism but only an indication of the existence of certain survival-favoring attributes. To be fit means to posses certain properties that increase the probability of survival. page 118

    The issue is with those “certain properties”. They could be just about anything- from the fastest to the slowest. From the tallest to the shortest. From the best eyesight to no sight at all. Etc., etc., etc.

    The point is to break the apparent tautology that is what is employed- according to Mayr.

  7. 7
    asauber says:

    “survival is not a property of the organism”

    I think Life is the most important property an organism can have. If an organism didn’t have Life, it wouldn’t even be an organism. 😉


  8. 8
    ET says:

    Living does increase the chance for reproduction, anyway. With the exception of male black widow spiders, of course.

  9. 9
    EDTA says:

    This seems like a worse problem than fitness/NS being a tautology. Aren’t these researchers saying that, since this discovery, they can’t even determine by direct measurement of population densities, which ones actually were the fittest? Do you have to wait 10 or 100 generations before you can tell whether a minority genotype will eclipse the current majority genotype? What does this do to every study of bacterial evolution done to date?

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