The Cambrian Explosion has long confused many prominent scientific figures, who have desperately tried to force the pieces of the evolutionary puzzle together, with limited success. If the latest research endeavors are anything to go by, however, perhaps researchers were being too narrow-minded?
The Cambrian Explosion
The Cambrian Explosion refers to a relatively short period in time when most of the Earth’s animal phyla burst into existence, some 580 million years ago. Before this period, organisms were relatively simple, consisting of individual cells that occasionally formed structured colonies. However, in accordance with fossil records, over the ensuing 70 to 80 million years, evolution appeared to accelerate at an astonishing rate, springing forth a highly diverse range of animals.
This highly extraordinary, almost inconceivable, rate of diversification even caused Charles Darwin to experience sleepless nights as he tried to piece the evolutionary puzzle together. The abrupt appearance of Cambrian fauna was also used by creationists to denounce the theory of evolution.
A Holistic Approach
Scientists have worked tirelessly to understand the reasoning behind this mysterious phenomenon, with a number of different scientific hypotheses being proposed. Dr. David Harper of the University of Durham explained that there were over 30 theories developed within the last decade.
Researchers working at Durham University believe a holistic approach must be adopted to understanding the Cambrian Explosion, once and for all, assimilating a host of different theories. Explanations fall into three broad categories – biological, geochemical and geological – with biologists favoring a biological basis, geologists favoring a geological basis, and so on.
The researchers were funded by the Agouron Institute, Geocenter Danmark and the Carlsberg Foundation, allowing their expedition to North Greenland to commence. The intrepid explorers were led by Professor Harper, who accessed the Arctic wastes using a Twin Otter series aircraft.
The team were located at Siriuspasset, some 500 miles from the North Pole. Although the trip presented certain dangers, the location was ideal for unraveling the mysteries of the Cambrian Explosion, since the fossilized remains were of exceptional quality.
Was a Global Sea Level Rise the Trigger?
The research group maintain the catalyst for the changes resulted from the rise in sea change, which then spurred a “cascade of events.” This increased the size of the habitable zone, providing an ideal environment in which diversification could take place, and helped drive a number of the other processes that fall under the biological, geochemical and geological categories previously mentioned.
This theory was originally coined by Shanan Peters, of the Department of Geoscience, University of Wisconsin, and Robert Gaines of the Geology Department, Pomona College. The pair used geochemical data to establish that ancient marine sediments caused expansion of “shallow epicontinental seas.”
The sea level rise helped to form shallow habitats, supported by sunlight and nutrients from erosion of fertile land. Organic life had to adapt to these new surroundings, promoting the rapid evolutionary processes seen during the Cambrian cycle and, eventually, spawned the type of lush, sprawling ecosystems that compare to those seen today.
An Evolutionary Arms Race
This extreme diversification facilitated the development of remarkable, evolutionary features, including the skeletal system, the advancement of the ocular system, the first jaw structures used for biting, and specialist attributes that allowed burrowing and swimming.
The general scientific consensus seems to support the notion that predator-prey interactions also stimulated an “arms race,” where a species’ survival was dependent upon evolution between sparring animals.
According to the Telegraph, organisms then had to respond to the seas filling with toxic calcium. In order to do this, animals had to find a means of expelling the calcium to guarantee their survival. Many scientists have posited that these diversifying organisms harnessed the calcium to form crystals, which eventually became shells and skeletal tissue. Predators then developed claws and jaws, whilst their prey replied through evolution of hardened structures, with which they could use to defend themselves.
Aside from this, another potential bottleneck may have been the levels of molecular oxygen available within the Earth’s earliest atmosphere. A recent study by Erik Sperling and his colleagues, based at Harvard University, looked at current environmental locations that replicate the conditions on Earth prior to the Cambrian Explosion. The regions contain little oxygen and, as a consequence, few to no carnivores dwell here.
When looking at all of the evidence, cumulatively, we start to see that the Cambrian Explosion can be explained by the interplay of a myriad of fascinating factors, as indicated by Harper and his colleagues. It is becoming clear that the Cambrian Explosion is an evolutionary puzzle, and we are only just beginning to assemble the intricate pieces of the puzzle together.
By: James Fenner