Octopuses Have An Ancient Antarctic Ancestor

In one of the most famous Hawaiian creation myths, Kane, the god of creation, makes a series of worlds. Each world contains a unique set of creatures and gods, and each is survived by a single species. The newest incarnation is the world of humans. So what is the sole remnant of the last world? According to the myth, it’s the octopus.

Interestingly, that’s exactly what a team of scientists has recently discovered. Over the past two years, 2,000 scientists from around the world have assembled a “census of marine life”, or an inventory of the oceans. One of the most fascinating findings of the census was that the octopus is a distant descendant of an ancient species that lived in the frigid waters around Antarctica. A modern octopus called the adelieledone, which also lives near the south pole, is the closest relative of the original creature. In a way, then, octopuses are remnants of a world that existed 30 million years ago.

So how did octopuses travel from the icy waters of Antarctica to fish markets, restaurants, and oceans across the globe? About 29 million years ago, a giant ice sheet covered the Southern Ocean. The extreme cold around Antarctica and the relatively warmer equatorial temperatures created cool ocean currents moving towards the equator. These currents carried the octopus ancestor to various parts of the ocean system, where it developed into different species.

According to the census, in isolation “many different species evolved; some octopuses, for example, lost their defensive ink sacs — pointless at perpetually dark depths.” Many other startling adaptations were found in other species, too: worms and shrimp, for example, that could withstand the heat of the ocean’s deepest volcanic vent. Or a carnivorous jellyfish that was found far deeper than was thought possible.

It won’t be surprising if there are many more discoveries in the near future. While we have a fairly dependable map of land species, the oceans have been a constant source of mystery. That’s partly due to the difficulty and expense of exploring deep, remote waters, but also partly due to a general fear of dark, unknown places. The 2007-2008 census was a major step in uncovering this “lost world”.