Scientists Offer Holistic Approach to Cambrian Explosion

In a remote region of Greenland just 500 miles from the North Pole, scientists are searching for clues that will offer more insight into the boom in animal life on Earth around 520 million years ago, and their latest study contends that it was a series of interconnected events, rather than a single underlying cause, that triggered one of the most significant biological events to have occurred on Earth.

The Cambrian Explosion, as the event is known, resulted in a hugely diverse array of species to emerge on Earth, many of which were the precursors to the animals we know today. The event led to a wide range of biological innovation, including specialist modes of life such as burrowing and swimming. Vertebrates also made their debut during the Cambrian Explosion, setting the stage for modern fish, birds, reptiles and mammals.

"The Cambrian Explosion is one of the most important events in the history of life on our planet, establishing animals as the most visible part of the planet's marine ecosystems," said David Harper of Durham University, who is one of the authors of a paper published in the journal Science, which suggests a more holistic approach to Cambrian Explosion origin theory.

Because the Cambrian Explosion was such a major biological event, there are a number of theories regarding what caused it. Most of the theories can be categorized as geological, geochemical or biological. Most Cambrian Explosion theories have suggested standalone processes that were the main cause of the explosion, but Harper and his colleagues disagree.

"It would be naïve to think that any one cause ignited this phenomenal explosion of animal life. Rather, a chain reaction involving a number of biological and geological drivers kicked into gear, escalating the planet's diversity during a relatively short interval of deep time," he said.

Harper, co-author Paul Smith of Oxford University and their colleagues say a "cascade of events" likely begun with an early Cambrian sea level rise. The rise would have expanded the rage of habitable sea floor, which in turn drove animal diversity. All these early events parlayed into a complex interaction of geological, geochemical or biological processes that are incorporated into the many standalone Cambrian Explosion theories.

"The Cambrian Explosion set the scene for much of the subsequent marine life that built on cascading and nested feedback loops, linking the organisms and their environment, that first developed some 520 million years ago," Harper said.

Professor Smith said: "Work at the Siriuspasset site in north Greenland has cemented our thinking that it wasn't a matter of saying one hypothesis is right and one is wrong. Rather than focusing on one single cause, we should be looking at the interaction of a number of different mechanisms.

"Most of the hypotheses have at least a kernel of truth, but each is insufficient to have been the single cause of the Cambrian Explosion. What we need to do now is focus on the sequence of interconnected events and the way they related to each other -- the initial geological triggers that led to the geochemical effects, followed by a range of biological processes."