Multicellular life evolved 60 million years earlier than previously believed, according to analysis of a new fossil.
The Cambrian Explosion began 542 million years ago, and was marked by the development of many of the major large groups of life present in the world today. The first skeletal animals developed during this time, and was believed to mark the rise of multicellular organisms.
The newly discovered fossil is roughly 600 million years old, which would signify the creatures that left behind the artifact lived 60 million years before paleobiologists believed they evolved.
"This opens up a new door for us to shine some light on the timing and evolutionary steps that were taken by multicellular organisms that would eventually go on to dominate the Earth in a very visible way. Fossils similar to these have been interpreted as bacteria, single-cell eukaryotes, algae, and transitional forms related to modern animals such as sponges, sea anemones, or bilaterally symmetrical animals," Shuhai Xiao, professor of geobiology in the Virginia Tech College of Science, said.
Phosphorite rocks collected from the Doushantuo Formation, located in the southern Chinese province of Guizhou, were examined by Xiao and his team. The researchers carried out the study in an effort to learn how multicellular lifeforms established dominance over the planet.
Fossils of eukaryotic cells (those that utilize oxygen) exhibit certain qualities, such as differentiation (cells serve specific purposes); adhesion is formed between the bodies, and cell death is pre-programmed. Plants, animals and other multicellular organisms are each composed of cells with these properties. Xiao examined the fossils for cell structures that exhibited similar qualities.
Chinese Academy of Sciences researchers also participated in the study of the newly discovered fossils.
Bacteria and other simple single-celled organisms known to be present on the Earth at that time would have been unable to create the intricate structures seen in the ancient artifacts. This discovery pushes back the evolutionary history of the planet, and ends several hypothesis regarding the evolution of multicellular creatures.
"This paper lets us put aside some of those interpretations," Xiao said.
However, it may still be possible that the fossils represent transitional forms of life, which could have been predecessors of multicellular algae and modern animals.
Findings of the investigators revealed information about how single-celled beings first began to coalesce, forming the world's first complex lifeforms.
Further research will focus on reconstructing the entire life cycle of the ancient beings, in order to learn how they lived.
Discovery of the ancient fossil and analysis of how the artifact pushed back the evolutionary history of the Earth was profiled in the journal Nature.
