How animals first appeared on Earth

Researchers at Australian National University have found the secret of how animals first appeared on the planet. This discovery explains the moment that led to the very existence of animals and humans on Earth.

Jochen Brocks, a professor of the ANU Research School of Earth Sciences, and his research team managed to unravel the mystery of the greatest ecological revolution in Earth’s history. They did so by analyzing ancient rocks from central Australia.

“We crushed these rocks to powder and extracted molecules of ancient organisms from them,” said Dr. Brocks. “These molecules tell us that it really became interesting 650 million years ago. It was a revolution of ecosystems, it was the rise of algae.”

Dr. Brocks explained that this rise of algae triggered the beginning of life as we know it.

“Before all of this happened, there was a dramatic event 50 million years earlier called Snowball Earth,” he said. “The Earth was frozen over for 50 million years. Huge glaciers ground entire mountain ranges to powder that released nutrients, and when the snow melted during an extreme global heating event rivers washed torrents of nutrients into the ocean.”

According to Dr. Brocks, cooling temperatures combined with exceptionally high levels of nutrients in the ocean created the perfect conditions for the rapid spread of algae. He said this was the catalyst for a shift from oceans filled with bacteria to a world inhabited by more complex life.

“These large and nutritious organisms at the base of the food web provided the burst of energy required for the evolution of complex ecosystems, where increasingly large and complex animals, including humans, could thrive on Earth,” said Dr. Brocks.

Co-author Dr. Amber Jarrett linked some of the ancient sedimentary rocks from central Australia to the time just after Snowball Earth melted.

“In these rocks we discovered striking signals of molecular fossils,” said Dr. Jarrett. “We immediately knew that we had made a ground-breaking discovery that snowball Earth was directly involved in the evolution of large and complex life.”

The findings of this study will be presented at the Goldschmidt Conference in Paris, France, this week and are published in the journal Nature.

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By Chrissy Sexton, Earth.com Staff Writer