"Darwin's Dilemma" --Enigma of Evolution's Cambrian "Big Bang" Solved
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September 12, 2013

"Darwin's Dilemma" --Enigma of Evolution's Cambrian "Big Bang" Solved

 

Cambrian_fossil_wide

 In the geologic timescale, the "Cambrian period" refers to the lowermost densely fossil-bearing rocks. These rocks record the sudden appearance of creatures, with representatives of almost every living phylum found fully formed and with no signs of evolutionary transition, which is an enigma for evolution.

“Darwin’s dilemma” refers to Charles Darwin’s bafflement that the fossil record contradicted what his theory of evolution predicted. In his classic book On the Origin of Species, Darwin declared that if his theory of evolution were true “it is indisputable that before the lowest Cambrian stratum was deposited… the world swarmed with living creatures.”

Yet Darwin admitted that the fossil record below the Cambrian strata seemed to be bereft of such creatures. Instead “species belonging to several of the main divisions of the animal kingdom suddenly appear in the lowest known fossiliferous rocks”—without any evidence of prior ancestral forms.

Darwin frankly acknowledged that this lack of ancestral forms was “a valid argument” against his theory. But he hoped that time—and more research—would provide the evidence that was lacking. Some 150 years later, the documentary Darwin’s Dilemma probes how Darwin’s dilemma has been aggravated—not resolved—by the last century of fossil discoveries, starting with the strange and wonderful creatures uncovered a century ago in the Burgess shale in British Columbia, Canada.

A new study led by University of 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, resolving "Darwin's dilemma" --the sudden appearance of modern animal groups in the fossil record during the early Cambrian period. In this study the scientists estimated that rates of both morphological and genetic evolution during the Cambrian explosion were five times faster than today - quite rapid, but perfectly consistent with Darwin's theory of evolution.

"It was during this Cambrian period that many of the most familiar traits associated with this group of animals evolved, like a hard exoskeleton, jointed legs, and compound (multi-faceted) eyes that are shared by all arthropods. We even find the first appearance in the fossil record of the antenna that insects, millipedes and lobsters all have, and the earliest biting jaws." says co-author Dr Greg Edgecombe of the Natural History Museum.

"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.

The team, including researchers from the Natural History Museum in London, quantified the anatomical and genetic differences between living animals, and established a timeframe over which those differences accumulated with the help of the fossil record and intricate mathematical models. Their modelling showed that moderately accelerated evolution was sufficient to explain the seemingly sudden appearance of many groups of advanced animals in the fossil record during the Cambrian explosion.

The research focused on arthropods (insects, crustaceans, arachnids and their relatives), which are the most diverse animal group in both the Cambrian period and present day.

The Daily Galaxy via University of Adelaide

Comments

Solved? "rates of both morphological and genetic evolution during the Cambrian explosion were five times faster than today." Sounds like fudge factoring to me.

What the authors are basically saying is, "The reason evolutionary progression was incredibly rapid during the Cambrian is because evolutionary progression was incredibly rapid during the Cambrian". The argument is a tautology that "solves" nothing.

why it was faster ? It WAS faster you and me can see it actually ... I mean that's why suddenly so many changes happened .... but why ? How are we proving this ?

The quote, "Darwin frankly acknowledged that this lack of ancestral forms was “a valid argument” against his theory," means to me that Darwin did not find a lot of evidence in the rock record prior to a certain period. This rock record evidence needs to be reviewed and analyzed more conclusively. Possibility of a asteroid strike or Mars supervolcano or partial evolution, may have all occurred along to way. Why not start with the idea all possibilities are on the table until proven other-wise. Its called scientific method!! Lets start the research new PHD candidates!

Oops! Something is still lacking: evidence.

"These rocks record the sudden appearance of creatures, with representatives of almost every living phylum found fully formed and with no signs of evolutionary transition, which is an enigma for evolution." -- A startling admission, rarely seen in print. Refreshing in its candor. I'm in agreement with skepticism expressed here, and further ask, is this a case of "manufacturing evidence"?

Those involved in the study "quantified the anatomical and genetic differences between living animals, and established a timeframe [ arbitrary? ] over which those differences accumulated with the help of the fossil record [ notoriously imperfect; and, of course, swarming with all manner of transitional forms, traceable in genetic-morphological lineage development ] and intricate mathematical models[?]. Their modelling [ how truly "scientific"? ] showed that moderately accelerated evolution was sufficient to explain the [ 'abrupt appearance' of ] groups of advanced animals".

Does that constitute "Dilemma"-solving evidence? Or yet another attempt to fill-in one of the gaping breaches in the Evolutionary Theory -- based on yet more hypothetical conjecture, over-built ( over-sold? ) with suppositional "modeling". If conclusion is based on an "intricate mathematical" model ( flawless, and which cannot be wrong ), then surely, it must constitute the final authoritative word. The critically reviewed(?) answer has been discovered: Case closed.

The recently reported Skull 5 findings http://www.sciencemag.org/content/342/6156/297 suggest a single species of Homo has existed on this planet for the past 1.8 million years. Reports of what have been considered species-wide changes are merely natural nutrient-dependent pheromone-controlled variations in morphology, which are exemplified in species from microbes to man.

I wonder if anyone will comment on the Cambrian Explosion in this context. Could evidence from the fossil record of species diversity also have been wrongly interpreted in the context of natural variations?


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