When did life first evolve from single-celled to multicellular organisms? That's a question that scientists have long struggled with. Now though, researchers may have uncovered one of the first multicellular organisms on our planet Earth.
Certain kinds of sedimentary rocks have the proper characteristics to preserve soft-bodied organisms as thin carbon films. During the Cambrian period, these deposits are more common. In addition, they preserve increasingly complex animals. However, only a few deposits from the Ediacaran period, which came before the Cambrian, are known to exist in the world.
That's why researchers decided to search for Ediacaran fossils in western Mongolia limestone. That's when they uncovered two ancient fossils.
In this latest study, researchers found fossils of two species of ancient multicellular marine algae, more commonly known as seaweed. These species of seaweed are actually some of the oldest examples of multicellular life on Earth.
"If you find a fossil from this time frame, you really need strong support for your interpretation of what it is," said Stephen Dornbos of the University of Wisconsin-Milwaukee. "And the farther back you go in geologic time, the more contested the fossil interpretations are."
This isn't all that surprising considering the age of the fossils in question. The fact that so few of these fossils exist also means that there's very little to compare them against. However, fossils from this time period are extremely important to scientists who want to learn a bit more about what happened on Earth during that particular period of time.
"This discovery helps tell us more about life in a period that is relatively undocumented," Dornbos said. "It can help us correlate the changes in life forms with what we know about the Earth's ancient environments. It is a major evolutionary step toward life as we know it today."
An explosion of animal diversity likely began near the start of the Cambrian Period, about 541 million years ago. However, these seaweed species that were recently discovered came from the preceding Ediacaran Period. This, in particular, shows that multicellular life first began to appear at that time.
The findings are published in the March 2016 journal Scientific Reports.
