A 555-million-year-old worm might be your oldest relative
In short: Deep in the rocks of South Australia lies a tiny, worm-like fossil that rewrites our evolutionary history. This creature, roughly the size of a grain of rice, represents a pivotal moment: the birth of bilateral symmetry, the blueprint for almost every complex animal on Earth today, from insects to humans.
Discovered in the Ediacara Hills of South Australia, the fossil dubbed Ikaria wariootia dates back approximately 555 million years. This makes it significantly older than the dinosaurs. While organisms like sponges are even more ancient, they lack the bilateral symmetry—a distinct front, back, and symmetrical left and right sides—that characterizes the majority of modern animal life.
The discovery was made using 3-D laser scanners from NASA to create high-resolution images of the fossils and the seafloor they inhabited. These scans revealed that Ikaria possessed a modular body structure and moved through sediment by extending and contracting its body, much like a modern earthworm. Crucially, it featured a through-gut system, where organic matter entered at one end and waste was expelled at the other, a fundamental anatomical milestone.
This find bridges a major gap in the fossil record. While DNA-based analyses predicted that the Ecdysozoa—a massive group containing over half of all animal species, including arthropods and nematodes—must have existed before the Cambrian period, physical evidence remained elusive. The discovery of Ikaria (and the related Uncus dzaugisi) confirms that these ancestors were present during the preceding Ediacaran period, providing a 'snapshot' of early animal evolution in a period of heightened diversity.
The study highlights a critical evolutionary leap: the ability to sense the environment, specifically locating food and oxygen. By developing these sensory capabilities and a segmented body plan, these early bilaterians laid the groundwork for the diverse range of life we see today. It suggests that while we look nothing like a grain-sized worm, the basic architectural modules of our bodies were established over half a billion years ago.
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Sources
- Summary by Intellect · source: This Worm-y Critter Is (Probably) Our Oldest Ancestor | SciShow News
- Also: Tiny Wormlike Creature May Be Our Oldest Known Ancestor
- Also: Tiny worm makes for big evolutionary discovery
- Also: www.newscientist.com — Worm-like fossil is the oldest ancestor of spiders and crustaceans | New Scientist
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