Sponge-like creature may be oldest animal ever found
THIS COULD just be our earliest ancestor – a sponge-like creature that didn’t have a gut and lived three-quarters-of-a-billion years ago.
Otavia antiqua was small, sometimes about the width of a human hair. It lived in the earliest oceans, in a world that had less oxygen in its atmosphere than today.
An academic paper, released this month in the South African Journal of Science, has announced Otavia as the earliest known animal. Microscopic Otavia fossils have been found across Namibia.
It also appears that this multicellular organism was a tough critter that survived one of the worst cold spells to grip planet Earth.
The discovery of these fossils is a culmination of 15 years of research by paleontologist Dr Bob Brain in the Namibian desert.
Brain is better known for his work on hominids and cave taphonomy, but since his retirement he has searched for the earliest traces of predation. It is his hobby, is how he describes it.
“I have been interested in predation, I just wanted to see where it all started,” explained Brain.
The oldest Otavia were around 760 million years old, a 150 million years earlier than when other animals emerged in the fossil record.
Co-author of the paper Dr Anthony Prave, of the Department of Earth Sciences at the University of St Andrews in Scotland, believes that Otavia would have lived in quiet water settings, like in lagoons.
“In general, oxygen levels would have been lower than today’s and temperatures probably somewhat warmer overall,” said Prave.
Otavia would have likely shared its world with algae and bacteria, both of which it preyed on.
Scientists believes how it fed has to do with the microscopic holes that can be seen across the bodies of these primitive sponges.
Beating flagella, tail-like structures on the outer body of Otavia, are believed to have drawn water with food matter into the organism.
Otavia didn’t have a gut, so its prey would have been drawn into the inner cavity, where it would be digested.
“Later, what is left over would be pushed out of those same small holes,” said Brain.
While temperatures might have been warmer than today, life – it appears – wasn’t always idyllic for the world’s earliest animal.
Prave, whose job it was to work out just when Otavia lived, discovered that the sponge was around before and after an event that scientists refer to as Snowball Earth.
This event makes the later ice ages appear like mild cold snaps.
Snowball Earth might have left the planet entirely frozen, with the seas iced up even at the equator.
There might have even been two Snowball events that Otavia survived.
“They (Otavia) are also found in rocks that occur between the two major Snowball Earth units in Namibia, and we have also found them in rocks that post-date the youngest Snowball Earth unit.
“So, yes, they evolved before Snowball Earth, survived through these events and existed too close to the Cambrian explosion (about 530 million years ago),” said Prave.
While Otavia might not have had the means to stalk its prey, Brain sees it as a predator, the first of its kind that started an evolutionary arms race.
He believes that, ultimately, what was started by Otavia led to man dominating the planet.
“We have done it (predation) better than others,” said Brain.