Wednesday, 25 June 2014

Biology's Big Bang: The Cambrian Explosion, some rational explanations

Welcome to the first part of a series of blogs investigating scientifically (but without the jargon), and re-evaluating the fossil record (which has always been problematic) and how it might be addressed and reinterpreted in the light of the most cutting edge discoveries in a wide range of fields from geology to physics and from physiology to palaeontology, thus providing us with a greater understanding of the deeper complexities of evolution. 


Most of us have heard about Biology's Big Bang, the Cambrian explosion, but here is a brief summary of what erupted in the period, just to refresh your mind:

"Prospecting around the town of Chengjiang, Hou and other researchers have since uncovered thousands of exquisitely preserved fossils that offer a glimpse back to a pivotal event in the history of life. This moment, right at the start of Earth’s Cambrian Period, some 550 million years ago, marks the evolutionary explosion that filled the seas with the world’s first complex creatures. In a blink of geologic time a planet dominated by simple spongelike animals gave way to one ruled by a vast variety of sophisticated beasts, animals whose relatives still inhabit the world today. This biological big bang reverberated through all facets of existence, altering not only the shape of animals but also the way they lived together".  

(source: Mysteries of the Orient 1993 )


Our more recent understanding & insights into the mechanisms for evolution can give us a clue to the cause of this explosion of life. E.g. stress induced triggers in cells of an organism during development and/or earlier evolutionary stage that can cause rapid, profound and inheritable real changes in an orgnaism in response to changing environment, is known as EPIGENTICS & this is causing a revolution in evolutionary thinking and explains a great deal. Could this explain the rapid and profound eruption of animal life in the Cambrian? Below is an excerpt from a recent paper that summarizes the epigenetic mechanism: See what you think yourself:

Linkoeping Universitet

"the ubiquity and universality of epigenetic systems is emphasized, and attention is drawn to the key roles they play, ranging from transducing environmental signals to altering gene expression, genomic architecture and defence.
What seems the most important factor about these epigenetic systems of control is that the changes are dynamic and typically can be rapidly induced in response to stimuli. Epigenetic systems therefore act as the conduit for information, both developmental and environmental in origin, to initiate short- and long-term gene expression changes"
 Ann Bot. Jan 2006; 97(1): 11–27.
PMCID: PMC2000771

Epigenetics and its Implications for Plant Biology 2. The ‘Epigenetic Epiphany’: Epigenetics, Evolution and Beyond

So if rapid changes in developing organisms can be triggered by environmental changes, then what could have been the trigger for the Cambrian explosion of life? Below is one very good candidate:


"We're proposing a triggering mechanism for the Cambrian explosion," says Peters. "Our hypothesis is that biomineralization evolved as a biogeochemical response to an increased influx of continental weathering products during the last stages in the formation of the Great Unconformity."

Peters and Gaines looked at data from more than 20,000 rock samples from across North America and found multiple clues, such as unusual mineral deposits with distinct geochemistry, that point to a link between the physical, chemical, and biological effects.

During the early Cambrian, shallow seas repeatedly advanced and retreated across the North American continent, gradually eroding away surface rock to uncover fresh basement rock from within the crust. Exposed to the surface environment for the first time, those crustal rocks reacted with air and water in a chemical weathering process that released ions such as calcium, iron, potassium, and silica into the oceans, changing the seawater chemistry.

The basement rocks were later covered with sedimentary deposits from those Cambrian seas, creating the boundary now recognized as the Great Unconformity".

Evidence for a geologic trigger of the Cambrian Explosion

April 18, 2012

That is the end of this little section. I'm afraid evolution is quite a hefty subject, so I'm doing it in bite-sized chunks. The next blog will look at the strange soft-bodied (embryo-like) life that existed prior to the Cambrian explosion and explore where these may have originated.

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