A 1.63 billion-year-old fossil may rewrite the history of multicellular life

A 1.63 billion-year-old fossil may rewrite the history of multicellular life

The first time Dr. Maoyan Zhu saw the fossil that would change the way he thought about early life on Earth, he was visiting his friend, Shixin Zhu, at his home in northern China.

“Next to Shixin’s sofa there were many beautiful fossils,” Dr. Zhu, a paleontologist from the Nanjing Institute of Geology and Paleontology, told Big Think. “One was exceptionally large, and it reminded me of modern seaweed fossils. When Shishen told me the rock was 1.56 billion years old, I immediately knew this was something special.”

Together with a team of researchers, the duo formally analyzed the fossil and published their findings in 2016. They described it as the oldest known multicellular eukaryotic organism, related to all animals, plants and fungi. Initially, the team did not name the fossil, choosing instead to focus on describing its important physical features rather than its taxonomic relationship to other species.

This serendipitous discovery would lead Dr. Zhu and his colleagues to a series of discoveries that culminated in the publication last January of another groundbreaking discovery: a 1.63 billion-year-old multicellular eukaryotic organism. The article was published in Advancement of scienceIt shows that early life on Earth was much more complex than scientists thought.

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Biologists divide life into two main categories: eukaryotes and prokaryotes. Eukaryotes, which include all animals, plants, and fungi, have cells that contain DNA surrounded by a nucleus, while prokaryotes contain free-floating DNA. Prokaryotes evolved about 4 billion years ago. The first single-celled eukaryotic organisms joined about 2 billion years later.

Before Dr. Zhu and colleagues’ 2016 publication of the large seaweed-like fossil, the oldest known multicellular eukaryotes dated back to 600 million years ago. This means that their 2016 discovery of the large, 1.56 billion-year-old fossil pushed the evolution of multicellularity back by a staggering billion years.

The discovery resonated with the scientific community and motivated Dr. Zhu and his team to further study the Yanshan region in northern China, where Shixin Zhou discovered the fossil. This time, the researchers looked for smaller specimens that contained well-preserved cell structures.

Dr. Zhou and another paleontologist from the Nanjing Institute, Dr. Lanyun Miao, had already collected and studied 1.63 billion-year-old shale rocks from the Quanlingguo Formation in the Yanshan area. Now, they looked at their samples with renewed interest and perspective, hoping to find more evidence of ancient multicellularity.

A series of images showing different types of fossils.

Microscopic images of Q: Great From the Chuanlinggou Formation. (Image source: Miao, L., Yin, Z., Knoll, A. H., Zhou, Y., and Zhu, M., Advancement of science2024.)

Eventually, they found what they were looking for: inside the shale samples were exceptionally well-preserved microfossils of… Kingshania magnifica. Using modern techniques, the team was able to conclusively prove that these specimens were multicellular eukaryotes.

This discovery extends the timeline for the evolution of multicellular organisms by an additional 700 million years and challenges fundamental assumptions about the pace of evolution and what life looked like billions of years ago.

Great question: The first multicellular organism?

The research team described Q: Great It contains cylindrical cells connected to cell walls, like modern plants. Some had spherical structures in the cells, indicating that they reproduced using spores. The team assumed so Q: Great It was photosynthesis, and although they couldn’t prove it, they suggested it might be an extinct group related to modern green algae today.

For Dr. Chu, the most interesting aspect of this finding was just that Q: Great Not much smaller than the oldest known single-celled eukaryotic organism. The fact that they are so closely together suggests that multicellularity evolved incredibly early in eukaryotes.

“The oldest single-celled eukaryotes are about the same age as these multicellular specimens. This is an interesting finding because it suggests that multicellularity evolved relatively early in the domain of eukaryotes. It may make people think differently about whether Difficult to evolve multicellularity from unicellular ancestor.

Dr. Zhou also pointed out another possible explanation: Scientists have yet to find the oldest single-celled eukaryotic organism.

“There may be a pre-history of eukaryotes that is still unknown to us, which may push the timeline of eukaryotic evolution even further into the past.”

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This highlights the challenges inherent in relying solely on fossil evidence, as many factors must combine perfectly to preserve biological material over millions of years. “Finding samples in these ancient layers is very difficult, especially 1.8 billion years ago, when intense tectonic activity made finding those ideal conditions even more difficult,” Dr. Zhu said.

“The Boring Billion” Revisited

The discoveries of Dr. Chu and his team — the large fossil and Q: Great – This means that these specimens lived in the Earth’s oceans during the “boring billion”, which is the period between 1.8 billion and 800 million years ago. As the name suggests, this era is characterized by minimal evolutionary and environmental change.

but, Q: Great It may make scientists rethink this era. As Dr. Chu puts it, “The boring billion might not have been so boring after all.”

“The observed lack of evolutionary change is probably a conservation issue – we don’t have the fossils – rather than a biological issue. The reality is that ancient specimens are difficult to study, and many people assume they won’t find much, anyway. I hope our findings will stimulate The Earth sciences community as a whole — paleontologists, chemists, and geologists — need to pay more attention to these ancient rocks and shed more light on what happened in the so-called “boring billion.”

However, the first complex multicellular organisms, with more advanced and diverse cells, did not appear until another billion years later Q: Greatafter the boring billionth and close to the documented Cambrian explosion about 541 million years ago.

“It seems that the step from single-celled eukaryotes to multicellular organisms did not take as long as we thought,” Dr. Zhou said. “But it stands to reason that the evolution of highly complex multicellular cells, which would lead to the world we see today, would require a much longer time frame.”

Rediscovery Q: Great

As for the name, kingshania magnifica, Dr. Chu said his team was looking at ideas for a name, assuming they were the first to officially discover the species. That was until they stumbled upon a 1989 paper published in an obscure Chinese journal, where they saw sections and a formal description that matched their sample. The authors of this early paper formally named this species as ““Kingchania Magnifica.”

“It shows what new approaches and renewed vision and context can do,” Dr. Chu said. “There is a lot of this lost research in obscure journals whose importance was not appreciated at the time. In many cases, the early researchers did not have the technology or tools to fully understand what they discovered.”

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