Ready your Kevin Costner jokes: A new study suggests that ancient earth had no continents to speak of and was instead what scientists call a "water world," reports the Guardian. In this case, ancient refers to 3.2 billion years ago, and the study in Nature Geoscience is based on the chemical analysis of a slab of ocean crust from that age in Australia. Such rocks "retain the chemical history of the oceans," explains Science Alert, and the story told by this rock suggests that one global ocean covered everything. "An early Earth without emergent continents may have resembled a 'water world,'" the scientists write. A few bits of land might have been jutting out of the water here and there, but otherwise it would have been water as far as the eye could see.
"There's nothing in what we've done that says you can't have teeny, micro-continents sticking out of the oceans," says Boswell Wing of the University of Colorado Boulder in a release. "We just don’t think that there were global-scale formation of continental soils like we have today." Researchers reached this conclusion by studying oxygen isotopes in the slab of ocean crust. They found more of one type, oxygen-18, than they should have had continents been around, because soil "disproportionately slurps up heavier isotopes like oxygen-18 from the water," per Science Alert. Assuming the findings are backed up by future work, they could give scientists a better understanding of when and where the first single-cell organisms sprang up on the planet. (Read more discoveries stories.)