Darwin’s dilemma resolved: Evolution’s ‘big bang’ explained by five times faster rates of evolution

Sep 15, 2013

 A new study led by Adelaide researchers has estimated, for the first time, the rates of evolution during the "Cambrian explosion" when most modern animal groups appeared between 540 and 520 million years ago.


The findings, published online today in the journal Current Biology, resolve "Darwin's dilemma": the sudden appearance of a plethora of modern animal groups in the fossil record during the early Cambrian period.

"The abrupt appearance of dozens of animal groups during this time is arguably the most important evolutionary event after the origin of life," says lead author Associate Professor Michael Lee of the University of Adelaide's School of Earth and Environmental Sciences and the South Australian Museum.

"These seemingly impossibly fast rates of evolution implied by this Cambrian explosion have long been exploited by opponents of evolution. Darwin himself famously considered that this was at odds with the normal evolutionary processes.

"However, because of the notorious imperfection of the ancient fossil record, no-one has been able to accurately measure rates of evolution during this critical interval, often called evolution's Big Bang.

Written By: Science Daily
continue to source article at sciencedaily.com

0 comments on “Darwin’s dilemma resolved: Evolution’s ‘big bang’ explained by five times faster rates of evolution

  • 1
    Alan4discussion says:

    A new study led by Adelaide researchers has estimated, for the first time, the rates of evolution during the “Cambrian explosion” when most modern animal groups appeared between 540 and 520 million years ago.

    Nobody has said evolution has to proceed at a uniform pace. Clearly when there is great pressure from environmental changes, or niches opened by extinctions, evolution is opportunist!

    This Cambrian “explosion of evolution” took 20 million years – which might be a faster change than other periods of evolution, but if it took a motor company 20 million years to bring out some revised models, we would not consider this to be “fast”!



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  • Never lost sleep over it tbh. A few dozens of millions of years is still a gargantuan amount of time. Whatever the process is, it would be based on some form of evolution, turbo-charged by new mechanisms, like sexual reproduction, predation, a drastic change in the environment, rapid mutations, punctuated equilibrium, ect… What else could it be, hey?



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  • 3
    OHooligan says:

    In reply to #2 by obzen:

    What else could it be, hey?

    Agreed, but good to see another “missing piece” filled in, more or less as anticipated. I love to see science advancing, it’s been doing it quite rapidly lately. Perhaps 5 times faster than previously observed…..



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  • Quoting Darwin’s Dilemma is anachronistic in my view. Back in his day there did seem to be a very sharp increase in ‘complex’ life forms ‘suddenly appearing’ in rocks of Cambrian age (a period spanning around 541-485 million years ago), but things have moved on a fair bit since then.

    Rocks of the pre-Cambrian Ediacaran Period (635-541 mya) have since been identified with a hugely varied and complex ecosystem, although most animals were soft bodied and didn’t tend to preserve very well, so they took a bit of hunting down (also a lot of the animals were so strange to our modern eyes that they took a while to be demonstrated to be animal fossils at all). This was further confused by the scientific ‘convention’ of Darwin’s day which stated that no complex life forms were present at all in any rocks of pre-Cambrian age, so Ediacaran rocks seen at the time were either misidentified as Cambrian or the odd looking fossil structures in them were classified as non-biogenic structures.

    These days we have acceptance for the Ediacaran aged fossils (and evidence for the first predators and first identified eyes within Ediacaran fossils, together with ancestral molluscs and arthropods which evolved to become dominant later in the Cambrian). Whilst most of the unique Ediacaran biota died out at or close to the onset of the Cambrian period, some forms were seen to hang on in there until around the middle Cambrian (510-500mya), so there was some significant overlap between Ediacaran and Cambrian biota.

    So the ‘Cambrian explosion’ does not currently look like the sudden explosion of complex life that a lot of people seem to be stuck on making it out to be – It just represents a (potentially rapid) change where what we now recognise as many ‘modern’ forms of animals (ie arthropods and molluscs in particular) diversified quickly and became dominant over the other pre-existing biota, at least in terms of the fossil records that they left behind.

    This is not a criticism aimed directly at this report, but I guess there are a lot of interested parties out there intent on ignoring relatively recent advances in our understanding of this fascinating period in the development of life, with the aim of maintaining the ‘Darwin’s Dilemma’ myth for their own ends.



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  • 5
    Zeuglodon says:

    In reply to #1 by Alan4discussion:

    A new study led by Adelaide researchers has estimated, for the first time, the rates of evolution during the “Cambrian explosion” when most modern animal groups appeared between 540 and 520 million years ago.

    Nobody has said evolution has to proceed at a uniform pace. Clearly when there is great p…

    To be frank, I’ve considered the Cambrian Explosion as not much more than a geological artefact. A blessing for palaeontology, certainly, but it isn’t proof of rapid evolution even of the gradualistic kind. The three most famous sites – the Burgess Shale in Canada, the Chengjiang site in Yunnan of China, and Sirius Passet in Greenland – are all unusual rock formations by fossil standards to begin with, and that’s because they preserved soft tissues and impressions which normally don’t fossilize.

    I predict that fossils will be found in Precambrian rocks that will disprove the notion of the Cambrian Explosion, and I base my prediction on genetic studies. I also predict that people will look back on this Cambrian Explosion idea with some degree of embarrassment as a result.

    If you go into genetic relationships, you get a totally different picture. The vertebrates most likely split away from the rest of the chordates (such as the sea squirts) during the Late Cryogenian and Early Ediacaran periods, though vertebrates themselves probably began to diversify during the Cambrian. This is before we even get to the rest of the invertebrates. You can find other examples of genetic studies on phylogeny here in the contents, and even look at the current results for any specific pair of taxa here — .

    If you look at animals in general, then the genetic evidence suggests most of them branched and diversified several hundred million years before the Cambrian. The last paragraph pretty much points out that the genetic studies “suggest that bilaterians had already radiated 100 million years or more before the Precambrian-Cambrian boundary”, and that attempts to establish a radiation closer to the Cambrian Explosion have been invalidated by faulty methodology. There’s little to no genetic support for the Cambrian Explosion.

    I think the Ediacaran Fauna provide a cautionary tale as well. Before it was discovered, most people didn’t think it was worth looking into Precambrian rocks because “everyone knew” complex life arose in the Cambrian. David Attenborough recounts this attitude in his TV show First Life, and I think a similar mindset might be behind the overrated hype of the Cambrian Explosion. I also remember Dawkins discussing this possibility in The Ancestor’s Tale.

    (N.B.: Use the expert result if you can. I’m not sure why, but the others seem to be inconsistent at times with the PDF chapters. For instance, Humans and Jellyfish versus Humans and Porifera are in their correct order in the PDF and the expert result, but not in the mean and median ones – an artefact of genetic study techniques?)



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