The remains of the oldest meal on record have been identified. In fossils of a strange slug-like creature called Kimberella, which lived half a billion years ago, scientists have found food molecules preserved in the gut, revealing what and how these ancient animals ate.
The Ediacaran period is when evolution really branched out and started experimenting with complex, multicellular life about 550 million years ago. Some of our oldest animal ancestors date back to this time, and they shared the world with some truly bizarre creatures unlike anything alive today. But details on how these animals lived are scarce.
In the new study, researchers at the Australian National University (ANU) investigated the eating habits of Kimberella, one of the most advanced lifeforms of its time. It looked a bit like a mollusk, with a shell-like outer body that could grow up to 15 cm (6 in) long.
In fossilized Kimberella specimens dating back 558 million years, the ANU team detected molecules of phytosterol preserved in its middle. This molecule is a type of fat found in plants, indicating it was the remains of the animals’ last meal. The larger implication of the find is that Kimberella had a mouth and a gut – quite innovative features for its time – and digested food in a similar way to modern animals.
“Scientists already knew Kimberella left feeding marks by scraping off algae covering the sea floor, which suggested the animal had a gut,” said Professor Jochen Brocks, co-author of the study. “But it was only after analyzing the molecules of Kimberella's gut that we were able to determine what exactly it was eating and how it digested food. Kimberella knew exactly which sterols were good for it and had an advanced fine-tuned gut to filter out all the rest.”
Most intriguingly, the team applied the same techniques to Kimberella’s contemporaries and found hints of other digestive techniques. A tube-worm-like creature called Calyptrina shared a similar gut structure and diet, but no sterol molecules were found in fossils of Dickinsonia. This animal looked like a large, ribbed pancake, growing up to 1.4 m (4.6 ft) long, and the team says it seemed to have no mouth or gut. Instead it likely absorbed food through its wide body as it moved around the seafloor.
The study helps scientists track the evolution of the earliest animals, and how they relate to their deep descendants today.
The research was published in the journal Current Biology.
Source: ANU