Hundreds of millions of years ago our planet experienced the mother of all ice ages. An event that not only turned the Earth into a giant snowball, but, according to research led by the Australian National University (Australia), probably also laid the foundation for a biological revolution. The answer to this ancient mystery has been found in ancient sedimentary rocks in central Australia in which organic molecules have been found trapped in the rock that suggest a global algal bloom after the ice melts.
Thus, the end of this frozen land epoch released large amounts of nutrients into the ocean and, thanks to them, increasingly complex algae and animals appeared.
“We crushed rocks into dust to extract molecules from ancient organisms. These molecules tell us that something really interesting happened 650 million years ago. It was the ecosystem revolution: the rise of algae,” explains Jochen Brocks , co-author of the work.
According to the researcher, the emergence of algae triggered one of the deepest ecological revolutions in Earth’s history, without which humans and other animals would not exist.
“Before all this happened, there was a dramatic event 50 million years earlier called Snowball Earth .” At that time, the Earth froze for 50 million years, and when the snow began to melt during an extreme global warming event, rivers threw torrents of nutrients into the ocean, kicking off this fabulous process of life.
The extremely high levels of nutrients in the ocean, and the cooling of global temperatures to more comfortable levels, created the perfect conditions for the rapid spread of algae.
“Those large and nutritious organisms at the bottom of the food chain (that is, algae) provided the energy blast necessary for the evolution of complex ecosystems, where ever larger and more complex animals, including humans, were able to thrive. “Brocks clarifies.
The sedimentary stones discovered by researcher Amber Jarrett were directly related to the period immediately after the melting of Snowball Earth. The experts used the preserved hydrocarbon biomarkers to gauge the exact timing of photosynthesis in complex organisms known as Archaeplastida , a large species of microbial predator that developed the habit of swallowing undigested cyanobacteria, forming an innovative society.
“In these rocks we discovered surprising signs of molecular fossils. We immediately knew that we had made a groundbreaking discovery that Snowball Earth was directly involved in the evolution of large and complex life,” says Jarrett.
Thus, we can now establish that between 663 and 645 million years old, at the end of the Sturtian ice age, the composition of life on Earth changed for the first time in its history.
Reference: Jochen J. Brocks et al, The rise of algae in Cryogenian oceans and the emergence of animals, Nature (2017). DOI: 10.1038 / nature23457
