Octopus DNA holds vital clues about past Antarctic ice sheet collapse and global sea-level rise. By analyzing genetic variation in modern octopuses, scientists have uncovered evidence of ancient population expansions and contractions that coincide with major climate events during the Cenozoic Era. These genetic signatures suggest that past episodes of ice sheet collapse, such as the Eocene-Oligocene Transition (EOT) around 34 million years ago, were linked to substantial increases in ocean temperatures and sea levels. By shedding light on the past relationship between ocean temperature, ice sheet stability, and sea-level change, octopus DNA contributes to our understanding of future projections of ice sheet behavior and global climate impacts.