Washington, May 11 : Scientists have attributed the cause of the "Cambrian Explosion", an event which may have sparked an ancient explosion of life 500 million years ago, to predation among animals.
The "Cambrian Explosion" - which occurred during the Cambrian Period 542 million to 490 million years ago - has puzzled scientists for years.
The Cambrian Explosion was unique because, though there have been mass extinctions - such as that of the dinosaurs - and recoveries since, there has never been another event as sweeping as that which occurred in the Cambrian seas 500 million years ago.
It was during that time when all the modern phyla of animals first arose. Phyla are major classifications of life that include broad groups of creatures.
The phylum Chordata, for example, includes all vertebrates, such as mammals, reptiles, amphibians, and birds.
Theories about the event's cause include an increase in the amount of atmospheric oxygen, a recovery from a global glaciation, and key genetic changes in precursor animals that allowed the development of bilateral symmetry, hard shells and bones, and rapid locomotion.
Now, Charles Marshall, Harvard Professor of Biology and of Geology, has come up with an alternative theory about the event.
This theory suggests that it was an increase in interactions between species, such as predation, that drove an escalating evolutionary process that led to the development of teeth and claws and the wide variety of characteristics that we see among Earth's animals today.
According to Marshall, it was possible that the creatures in the pre-Cambrian seas during the Ediacaran Period didn't entirely disappear.
Though they were very different from what followed, they may have been genetically complex enough to hold the genetic seeds of the explosion.
"It's not new genes that create new morphological innovation, but rather the way they're wired together," said Marshall.
If the precursors to the creatures that arose during the Cambrian Period were swimming in the Ediacaran seas, something had to spark the dramatic change.
Marshall began to search for an environmental force that might have driven such dramatic change in the fleshy animals that populated the oceans before the Cambrian began.
He realized that those creatures had no organs of interaction and began to think that the new force on the scene was the ability of animals to interact with each other.
"Ediacarans were not interacting with each other as animals do today," said Marshall. "I think what drove the Cambrian Explosion was ecological interactions," he added.
The trigger that sparked those changing interactions might have been something as simple as the evolution of jaws with toothlike projections that allowed the world's first painful bite.