500-million-year-old purple blob may be Earth's earliest animal

In the vast, arid landscape of South Australia’s outback, a fossil record lies hidden beneath the soil, holding crucial clues to Earth’s early evolutionary history. 

These fossils, found in Nilpena Ediacara National Park near South Australia’s largest mountain range, document a pivotal moment in the emergence of complex life. 

This recent discovery has provided new insights into how single-celled organisms evolved into complex animals.

Fossils of 555-million-year-old animal

A team led by Scott Evans, assistant professor of geology at Florida State University, has unearthed a significant fossil of an early marine animal called Quaestio simpsonorum. 

This 555-million-year-old creature is the first known to exhibit left-right asymmetry, a crucial feature in the evolution of complex life.

“The animal is a little smaller than the size of your palm and has a question-mark shape in the middle of its body that distinguishes between the left and right side,” Evans explained. 

“There aren’t any other fossils from this time that have shown this type of organization so definitively. This is especially interesting as this is also one of the first animals that was capable of moving on its own.”

Movement of Earth’s earliest animals 

Researchers believe Quaestio moved along the seafloor much like a “marine Roomba,” feeding on nutrients from microscopic organisms and bacteria. 

Evidence of this movement was preserved in fossilized rock slabs that display impressions of the animal along with its trace fossils. 

The texture of the preserved mat, where Quaestio left its trails, reveals the organic richness of the early seafloor ecosystem.

Exciting discovery in Nilpena Ediacara National Park

While Nilpena Ediacara National Park is already famous for its fossil beds, the discovery of Quaestio marks a major milestone. 

The excavation team, which included researchers from institutions like Harvard University, the University of California, Riverside, and the University of Adelaide, made a critical discovery when they found clear evidence of the creature’s movement. 

“One of the most exciting moments when excavating the bed where we found many Quaestio was when we flipped over a rock, brushed it off, and spotted what was obviously a trace fossil behind a Quaestio specimen – a clear sign that the organism was motile; it could move,” said co-author Ian Hughes, a Harvard University graduate student.

Earliest animal life on Earth

For more than 20 years, the team has been guided by Mary Droser, distinguished professor of geology at UC Riverside. Droser has led excavations in the outback, and this latest discovery offers new insights into how animal life unfolded on Earth. 

“It’s incredibly insightful in terms of telling us about the unfolding of animal life on Earth,” Droser remarked. 

The Nilpena fossil record allows scientists to study the processes that shaped the origins of complex life, from the earliest evolutionary developments to the events leading to species extinction.

Genetic programming in the earliest animals

The discovery of Quaestio simpsonorum is particularly important because it sheds light on early animal development. 

Evans noted that determining the gene expressions needed to build these forms provides a new method for evaluating the mechanisms responsible for the beginnings of complex life on this planet.

The left-right asymmetry exhibited by Quaestio is mirrored in modern animals, suggesting that the same genetic programming has been at work for over half a billion years.

This finding is not only a major breakthrough in understanding early evolutionary processes but also provides a unique window into life during the Ediacaran period. 

The team believes that studying these ancient fossils will continue to yield new insights into how complex life evolved and adapted on Earth.

A growing legacy and ongoing excavations

Nilpena Ediacara National Park, which opened to the public in 2023, is in the process of being recognized as a UNESCO World Heritage Site. 

This recognition is largely due to the work and dedication of Mary Lou Simpson and Antony Simpson, founders of the Flinders Ranges Ediacara Foundation. The discovery of Quaestio simpsonorum, named in their honor, is one of many exciting finds that have emerged from the park’s 150,000-acre fossil beds.

Although researchers have been studying this area for decades, new discoveries continue to be made. 

“We’re still finding new things every time we dig,” Hughes said. This park, one of the world’s earliest ecosystems, continues to astonish scientists with its rich and diverse fossil record. 

These ancient discoveries offer invaluable insights into the earliest chapters of animal evolution and continue to fuel the quest to understand the origins of life on Earth.

The study is published in the journal Evolution & Development.

Image Credit: Walker Weyland

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