In a seemingly unremarkable rock, the remains of some deep-sea sponges could be found. If they are as old as some scientists suspect, they would be the oldest animal fossils ever discovered. Elizabeth Turner, a geologist, stumbled upon some stones with distinctive grooves while on an expedition through Canada’s Mackenzie Mountains in 1992. She suspected they might be fossils, but at the time, research in this area was not advanced enough to confirm her suspicions. The stones remained in Turner’s cabinets for several years until Canadian researchers published a study in 2007 showing that sponges could be preserved as fossils in limestone.
Turner retrieved the stones when she learned of the new study. The limestone in which the strange tubes were found was quickly dated to about 890 million years ago. However, were the grooves actually sponge fossils, or were they the remains of a single-celled organism? Turner claimed in a study published in the journal Nature that they were sponges, but many scientists remain skeptical. It is currently believed that sponges emerged 540 million years ago, making them one of the earliest animals on Earth. If Turner’s suspicions are correct, the sponges would have lived during a time of extremely low oxygen levels.
Despite Turner’s detailed study, many scientists remain unconvinced. Jonathan Antcliffe, a Swiss paleobiologist who was not involved in the study, wrote, “Everything we know about Earth’s history tells us that the first living things emerged about 540 to 550 million years ago. To change this massive body of evidence requires more than statements like ‘this could be a sponge.'”
