A major tectonic event may have triggered the rise in sea level and other environmental changes that led to the Cambrian explosion, the sudden burst of animal life 530 million years ago, showed a research.
The new analysis of geologic history may help solve the riddle of the Cambrian explosion that has puzzled scientists since the time of Charles Darwin.
The sudden burst of new life is also called 'Darwin's Dilemma' because it appears to contradict Charles Darwin's hypothesis of gradual evolution by natural selection.
"At the boundary between the Pre-cambrian and Cambrian periods, something big happened tectonically that triggered the spreading of shallow ocean water across the continents, which is clearly tied in time and space to the sudden explosion of multi-cellular, hard-shelled life on the planet," said Ian Dalziel, professor at The University of Texas, Austin in the US.
Apart from the sea level rise, the ancient geologic and geographic changes probably led to a build-up of oxygen in the atmosphere and a change in ocean chemistry, allowing more complex life forms to evolve, he added.
The study integrated geological evidence from five present day continents - North America, South America, Africa, Australia and Antarctica - to ascertain the paleo-geography of that critical time.
The study appeared in the journal Geology.