Guy Threepwood
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- Oct 16, 2019
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Eh, not really: Integrated records of environmental change and evolution challenge the Cambrian Explosion | Nature Ecology & Evolution
Holistic integration of fossil and geochemical records leads us to challenge the notion that the Ediacaran and Cambrian worlds were markedly distinct, and places biotic and environmental change within a longer-term narrative. We propose that the evolution of metazoans may have been facilitated by a series of dynamic and global changes in redox conditions and nutrient supply, which, potentially together with biotic feedbacks, enabled turnover events that sustained multiple phases of radiation. We argue that early metazoan diversification should be recast as a series of successive, transitional radiations that extended from the late Ediacaran and continued through the early Palaeozoic. We conclude that while the Cambrian Explosion represents a radiation of crown-group bilaterians, it was simply one phase amongst several metazoan radiations, some older and some younger.
I'd agree with that in general, yes there were a lot more explosions/radiations than the Cambrian- that just happens to be best known. I'd say this just further undermines the Darwinian hypothesis (as argued by some here) that macro evolution is merely an extension of slow gradual natural variation.
This also drastically increases the problem of accounting for vast new volumes of genetic information spontaneously appearing in ever shorter timescales, by sheer chance. Some attempt to account for this by explosive solar/supernova radiation events since the known waiting times for mutations would have had to have been accelerated dramatically. Here again we run into the mathematical hurdles of deleterious mutations vastly outnumbering advantageous ones
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