Researchers from the University of California Riverside found the oldest-ever evidence of the first multicellular animal on earth, which appeared in a hostile period of earth’s history in which the planet was frozen almost solid.
According to the new study, ancient sea sponges called Demospongiae emerged 635 to 660 million years ago. The mid-Neoproterozoic era marked extreme circumstances for life on earth—almost the entire earth was covered in ice in what's known as the Marinoan glaciation, caused by "Snowball Earth" conditions. As this global ice cap melted, oxygen dissolved in the ocean water, providing just the right conditions for early multicellular organisms to emerge.
The results of the study constitute “the earliest robust biomarker evidence for Neoproterozoic animals,” according to the paper.
Back in 2009, these same researchers found evidence that Demospongiae emerged during this period. However, their findings weren’t universally accepted.
Jonathan Antcliffe, a scientist now at the the University of Lausanne, pointed out at the time that the biological marker that the UC Riverside researchers studied isn't exclusive to ancient sponges. The same molecule, 24-isopropylcholestane, is also found in pelagophyte, a type of ancient marine algae. Meanwhile, this study examined evidence from the steroid 26-methylstigmastane is believed to be unique to Demospongiae.
In other words, the new research provides the most solid proof yet that animals emerged extremely early in earth’s history, thriving within frigid ancient glacial meltwater. “We have effectively doubled up the evidence [from 2009],” paper author Gordon Love said in an email to Motherboard.
According to the research paper, it’s possible that even older evidence of multicellular animals exists in samples from the Chuar Group, a group of ancient rocks in the Grand Canyon, and the Visingsö Group in southern Sweden. However, that evidence has not yet been confirmed.
Love told Motherboard that in the future, his research teams wants to unpack the genetic quirks that made the emergence of animals possible.
“We are interested in identifying the genes involved in unconventional steroid synthesis that makes the sterol precursors of 26-mes,” Love said. This genetic analysis, Love said, could tell scientists if ancient sea sponges passed their genes on to other parts of the animal kingdom.