Fossil of a Trilobite – Cheirurus ingricus – from the early Cambrian period (Tim Evanson/Creative Commons via Flickr)
Last week we told you about an Australian study that suggested that the evolution of life during the Cambrian Explosion took place at five times the rate it occurs today.
Now, another group of scientists from Britain, in their newly published study, weigh in on the “Big Bang of Life.” They propose that the explosion of animal life on Earth that took place some 520 to 540 million years ago was not the result of just one single principal cause, but rather from a combination of interwoven factors.
The Cambrian Explosion, the researchers said, was a major evolutionary event that led to a wide range of biological innovation, which included the beginning of modern ecosystems, a rapid increase in animal diversity, the origin of skeletal creatures and the first appearance of specialist modes of life such as burrowing and swimming.
Animals that made their first appearances on Earth during the Cambrian explosion, according to the researchers, included vertebrates such as the distant ancestors of modern fish, reptiles, birds and mammals.
The British researchers suggested that in order to determine the reasons behind the Cambrian Explosion, scientists need to take a more ‘holistic approach’ that encompass a range of factors.
A number of odd looking lifeforms, like the Anomalocaris, pictured in this model, came out of the Cambrian explosion. Model on display at the National Dinosaur Museum, Canberra, Australia. (Phonart via Wikimedia Commons)
“This is a period of time that has attracted a lot of attention because it is when animals appear very abruptly in the fossil record, and in great diversity. Out of this event came nearly all of the major groups of animals that we recognize today,” said Paul Smith, lead author of the study and director of the Oxford University Museum of Natural History.
“Because it is such a major biological event, it has attracted much opinion and speculation about its cause,” Smith said.
Over the years there have been a number of theories about the Cambrian Explosion. The researchers said that those concepts, which fall into three main categories – geological, geochemical and biological — are separate and exclusive processes that also suggest a single cause of the explosion.
The researchers said that they consider the Big Bang of Life was the result of a “cascade of events,” more of a complex interaction of those biological, geochemical and geological processes that were suggested in those individual theories.
“It would be naive 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,” said David Harper, co-author of the study and a professor of paleontology at Durham University.
Some consider the long extinct Haikouichthys (artist rendering), that emerged from the Cambrian explosion, one of the earliest fishes on Earth (Talifero via Wikimedia Commons)
The British researchers propose that the causes behind the explosion of animal life probably began with an early Cambrian rise in sea level.
This sea level rise, they said, generated a large increase in the area of habitable seafloor, which in turn drove an increase in animal diversity.
The team of scientists, led by Smith and Harper, wrote their study after working for four years from data that was gathered from a site that faced the Arctic Ocean in northernmost Greenland.
The team was attracted to the site, which they said was difficult to reach, because of the high quality of its fossil material and the insights it provided.
The research team’s findings can be found in the latest edition of the journal Science.
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