A geobiologist from Virginia Tech, in collaboration with researchers from the Chinese Academy of Sciences, have found something that puts the entire evolutionary timeline in question.
The research team found evidence in the fossil record that complex multicellularity appeared in living things about 600 million years ago. That’s nearly 60 million years before skeletal animals appeared during the Cambrian Explosion — a period of time on Earth when an immense growth spurt of life occurred.
The journal Nature published the findings, which contradict many longstanding interpretations of multicellular fossils from up to 600 million years in the past.
Shuhai Xiao, a professor of geobiology at the Virginia Tech College of Science, talked about how researchers would have to alter their understanding of evolution based on the new evidence.
“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. This paper lets us put aside some of those interpretations.”
So what does all this mean? The spherical fossils found in southern China aren’t likely to be bacteria or single-cell protists, but rather some of the world’s earliest animals. The cells of the animals — preserved in rock for 600 million years — are too complex for single-celled organisms. Each fossil found measured about.003 inches across, and came from what would have been a shallow marine environment. At first, Dr. Xiao thought that the fossils might be from animal embryos, but no matching adult that has ever produced such an embryo has ever been found.
Something else interesting about the fossilized animals, dubbed Megasphaera, was the ellipsoidal structure growing within it. The researchers nicknamed the structures “matryoshka.” The researchers have deduced that the Megasphaera represent a group of early animals that did not go on to be a common ancestor of any modern living creatures.
In the end, the discovery may actually strengthen the evolutionary timeline, as the fossils could represent the transition between single-celled life and multicellular animals, according to NBC News. However, there is also a possibility that the fossils are not even animals. Xiao said that the anatomy is also consistent with algal life forms, which means that the fossils could be more plant-like than animal.
[Image via NBC News]