Snowballs and Algae
This week, in a press release, the Australian National University asserted that a team of their scientists had figured out how animal life came into existence on our planet. The release states, "Research led by The Australian National University (ANU) has solved the mystery of how the first animals appeared on Earth, a pivotal moment for the planet without which humans would not exist."
The discovery started with ancient sedimentary rock samples from central Australia. The team, led by ANU Research School of Earth Sciences associate professor Jochen Brocks, crushed the rock samples into powder and then "extracted molecules of ancient organisms from them," Brocks explained in the press release. "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."
Scientists generally agree that complex, animal life on Earth started some 600 million years ago. Brocks and his team claim that a significant event preceded this. "Before all of this happened, there was a dramatic event 50 million years earlier called Snowball Earth," he said, referring to a hypothesis that suggests a period when the planet's surface was entirely frozen from pole to pole.
This event is key for the ANU team's findings, as it was what made the growth and spread of algae possible. "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," Brocks explained.
At the end of this frozen period, when global temperatures settled into more hospitable levels, the nutrients that flooded into the oceans sparked the transition from microbial life into a more complex life, Brocks said. "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," he added.
This study is, indeed, promising and could potentially be groundbreaking. The origin of complex life on Earth remains one of the most puzzling events in science, as the evolutionary jump between single-celled microbes and multi-cellular, nucleus-bearing, mitochondria-powered organisms is simply immense.
Additionally, our understanding of the moment this occurred keeps on evolving. While it's understood that conditions on Earth became ideal at a certain point to make life possible, being able to pinpoint just what these conditions were — and exactly when they occurred — could better help explain complex life's rise.
Studies like this ANU research help in achieving this. Recently, a couple of studies have been published that also attempted to shed light into the origin of life on Earth. One suggested that life didn't just begin in the oceans, but also on land. Another claimed that the so-called Asgard microbes are the bacterial ancestors of human life.
Studying the origins of life on this planet could also help us to figure out how life develops in the cosmos. Right now, the search for extraterrestrial life is a concern that keeps a number of scientists and institutions occupied. Understanding life on Earth might just help us understand life beyond it.