‘Ancestor Of All Animals’ Discovered In 555-Million-Year-Old Australian Fossils

Published March 24, 2020

"This is what evolutionary biologists predicted. It’s really exciting that what we have found lines up so neatly with their prediction."

Fossilized Burrows Of Ikaria Wariootia

University of California, RiversideMany experts didn’t think such tiny, prehistoric fossils would ever be found. Fortunately, modern technology proved them wrong.

Researchers have just uncovered evidence of a 555-million-year-old worm-like creature in Australia. As if that wasn’t exciting enough, experts believe this is the first ancestor of all animals — including humans.

According to Phys, this creature is named Ikaria wariootia and it is the earliest bilaterian — an organism with a front and back, two symmetrical sides, and openings at either end connected by a gut.

The team of geologists from the University of California, Riverside recently published their new research in the Proceedings of the National Academy of Sciences journal. And experts couldn’t be more thrilled with the results.

“This is what evolutionary biologists predicted,” said geology professor Mary Droser. “It’s really exciting that what we have found lines up so neatly with their prediction.”

Fossilized Ikaria Wariootia In Stone

University of California, RiversideWith a ruler for comparison, it’s clear just how small the creature’s fossilized burrows really are.

The earliest multicellular organisms, collectively known as Ediacaran biota, had variable shapes. This group holds the oldest and most complex fossils of multicellular organisms. However, most of them aren’t directly related to modern-day animals. For instance, they often lacked mouths or guts.

As such, evolutionary biologists studying the genetics of modern animals believed the oldest ancestor of all bilaterians was likely small and simple, with very basic sensory organs.

With experts eagerly attempting to find fossilized evidence of the oldest ancestor of animals, this geological research team has made an unprecedented mark in the field. After all, the development in bilaterian body structure was a crucial step in the evolution of animal life.

From worms to dinosaurs to modern-day people, a multitude of animals are all organized around this basic bilaterian body plan.

Of course, since the earliest Ediacaran biota creatures were so tiny, most evolutionary biologists were convinced that they would never find their fossilized remains. Fortunately, with modern technology comes potential — with 3D laser scans leading these experts to victory.

3d Scan Of Ikaria Wariootia Fossils

University of California, RiversideA modern 3D scan such as this one allowed researchers to see the vital features of early worm-like creatures.

The discovery was made in Nilpena, South Australia, where fossilized burrows date back to the Ediacaran Period about 555 million years ago. Researchers have known for about for 15 years that bilaterians somehow created these fossils, but haven’t had the tools to confirm their prehistoric presence — until now.

Droser and doctoral graduate Scott Evans noticed impressions near these burrows, which 3D laser scans confirmed were shaped and sized like a grain of rice. They also revealed clear heads, tails, and even grooves that suggested the presence of muscles.

Contracting those muscles allowed the creatures to move around, not unlike how modern-day worms do today. Furthermore, the observed patterns of displaced sediment, in addition to signs of feeding, suggested the creatures had mouths, guts, and posterior openings.

“Burrows of Ikaria occur lower than anything else,” said Droser, referring to their site of discovery being in a low layer of Nilpena’s Ediacaran Period deposits. “It’s the oldest fossil we get with this type of complexity. We knew that we also had lots of little things and thought these might have been the early bilaterians that we were looking for.”

An interview with geologist Mary Droser as she works in Nilpena, Australia.

“We thought these animals should have existed during this interval, but always understood they would be difficult to recognize,” said Evans. “Once we had the 3D scans, we knew that we had made an important discovery.”

As for the newfound creature’s name, Ikaria means “meeting place” in Adnyamathanha — the language of the indigenous Australians who live in the region. Meanwhile, wariootia refers to the local Warioota Creek.

In the end, it’s remarkable to see such minuscule impressions in stone make such an enormous impact — one which showcases some of the most fundamental steps of our collective evolutionary history.

After learning about the oldest ancestor on the animal family tree, read about the 90-million-year-old Ichthyosaurus fossil found in an Englishman’s yard. Then, learn about the 518-million-year-old sea creature fossil shedding new light on ocean evolution.

Marco Margaritoff
A former staff writer for All That’s Interesting, Marco Margaritoff holds dual Bachelor's degrees from Pace University and a Master's in journalism from New York University. He has published work at People, VICE, Complex, and serves as a staff reporter at HuffPost.
Jaclyn Anglis
Jaclyn is the senior managing editor at All That's Interesting. She holds a Master's degree in journalism from the City University of New York and a Bachelor's degree in English writing and history (double major) from DePauw University. She is interested in American history, true crime, modern history, pop culture, and science.
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Margaritoff, Marco. "‘Ancestor Of All Animals’ Discovered In 555-Million-Year-Old Australian Fossils." AllThatsInteresting.com, March 24, 2020, https://allthatsinteresting.com/ikaria-wariootia-fossils. Accessed May 21, 2024.