The early animals on Earth did not require much oxygen in the past. According to study conducted by Daniel Mills of the University of Southern Denmark, the most primitive creatures in the planet may have survived in water with barely little oxygen.

Research findings suggested the rise of animals from the water may have been the beginning of modern oceans rich in oxygen.

Like the world's first animals, sponges can thrive in water with low levels of oxygen. The findings challenged the existing world's view that evolution of animals was delayed due to lack of oxygen. But the latest study supported the theory that the early animals assisted in increasing the oxygen levels on Earth.

Mills and his colleagues gathered breadcrumb sponges and kept them in an aquarium. They gradually removed the oxygen and found that the sponges can survive even if there is 200 times less oxygen in the water. The sponges were still alive after 10 days of the experiment. The researchers concluded early animals could probably survive with less oxygen since modern sponges can.

The first microbes on Earth evolved roughly 3.6 billion years ago but multicellular organisms and other forms of complex life didn't appear for another 3 billion years. Scientists believed it was also about the time that oxygen levels in the atmosphere increased dramatically to reach modern day levels of 20 percent. Many experts supported the theory that animals needed higher concentrations of oxygen to evolve and thrive.

CarriAyne Jones, a researcher from the University of British Columbia who helped with the study, said sponges have an organized structure with a network of channels to use food and water. The sponges raised in the lab inside the aquarium can survive with only 0.1 percent of oxygen.

The findings of the study were published in the Proceedings of the National Academy of Sciences on Feb. 17.

RELATED STORIES