Studies on a small sea sponge have found that complex life does not require high levels of oxygen to survive and grow.
The origin of complex life is one of science's greatest mysteries. How could the first small primitive cells evolve into the diversity of advanced life forms that exists on Earth today? The explanation in all textbooks is: Oxygen. Complex life evolved because the atmospheric levels of oxygen began to rise app. 630 - 635 million years ago.
However new studies of a common sea sponge from Kerteminde Fjord in Denmark showed that animals can live and grow even with very limited oxygen supplies.
In fact animals can live and grow when the atmosphere contains only 0.5 per cent of the oxygen levels in today's atmosphere.
"Our studies suggest that the origin of animals was not prevented by low oxygen levels," lead author Daniel Mills, PhD at the Nordic Center for Earth Evolution at the University of Southern Denmark, said.
The study was published in the journal PNAS.