The 75% of animal life you likely overlook every day

Nature · Published 25 October 2026 Swipe more like this →

In short: Arthropods are the most successful architects of our planet's biodiversity. From garden spiders to deep-sea crustaceans, these jointed-leg invertebrates dominate nearly three-quarters of all animal species on Earth, serving as the essential recyclers and pollinators that keep our ecosystems functioning.

Arthropods are defined by their jointed legs and invertebrate bodies, but their true significance lies in their ecological versatility. They function as primary pollinators, nutrient recyclers, scavengers, and a foundational food source for countless other species. This diversity spans four major groups: insects, myriapods (such as centipedes and millipedes), arachnids (including spiders, mites, and scorpions), and crustaceans (which include crabs, prawns, and slaters).

The evolutionary history of these creatures is staggering. Their ancestors first appeared in the oceans approximately 530 million years ago during the Cambrian period—a timeframe that scientists still only incompletely understand. They have survived for hundreds of millions of years by successfully adapting to radically shifting environments, allowing them to colonize nearly every corner of the globe.

Despite their ubiquity, the 'phylogeny'—the evolutionary tree—of arthropods remains one of biology's most unresolved puzzles. Scientists currently face conflicting ideas regarding how these groups diversified from common ancestors. To solve this, researchers at institutions like the Australian Museum are using high-tech tools such as DNA sequencing, electron microscopy, and computer-aided phylogenetic analysis to decode these deep evolutionary branches.

Because so much time has passed, finding clues to early ancestry requires a targeted approach. Researchers focus on specific 'living fossils' or basal lineages that are most likely to preserve ancestral traits. To map out a highly effective biological blueprint's past, scientists examine diverse species like silverfish, leptostracan shrimps, velvet worms, scorpions, and king crabs (or horseshoe crabs).

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