How Squid Survived Earth's Biggest Mass Extinction and Took Over the Ocean — Scientists Finally Know

Scientists have cracked the mystery of how squid and cuttlefish survived the Permian mass extinction and became ocean dominants. Here is what newly sequenced genomes reveal.

The Permian-Triassic extinction event of approximately 252 million years ago — the largest mass extinction in Earth's history, which eliminated an estimated 96 percent of all marine species — is the event that most dramatically reset the configuration of ocean life. Understanding why some lineages survived it and why many did not has been one of evolutionary biology's most persistent and consequential questions. A new study published in April 2026, involving newly sequenced genomes from squid and cuttlefish species analysed alongside global ecological datasets, has produced the clearest account yet of how these remarkable animals not only survived the extinction but emerged from it to become dominant features of ocean ecosystems.

The key finding involves a specific genetic architecture that squid and cuttlefish share — a suite of genes controlling metabolic flexibility, immune response, and developmental plasticity that appears to have allowed these animals to survive the extreme ocean chemistry changes that accompanied the Permian extinction. The extinction's oceanic dimension involved not just temperature increase but dramatic acidification, deoxygenation, and shifts in the chemical composition of seawater that eliminated animals whose metabolisms were precisely calibrated to pre-extinction conditions.

Squid and cuttlefish, the research suggests, possessed a metabolic range that allowed them to tolerate these changing conditions better than their competitors. Their ability to shift between different metabolic strategies — essentially, to run their biology on different chemical fuels depending on what was available — provided a resilience that more specialised ocean predators lacked.

The modern relevance of this finding is not merely historical. Ocean acidification, driven by CO2 absorption from the atmosphere, is progressing at a rate that some projections suggest will produce ocean chemistry changes not seen since the Permian within centuries. Understanding which marine lineages are likely to tolerate future ocean chemistry changes, and why, is exactly the kind of knowledge that the squid genome research provides.